ksp fuel transfer
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ksp fuel transfer Post Review
Stelvy took two tourists to Munar orbit & onwards to a Minmus landing. If I had a science point for every landing I’ve done on a fuel tank I’d have an ion engine... 😉 Fantastic 29m/s transfer between moons, 320 ablator is usually enough for a harsh reentry or two #KSP https://t.co/YR76lwJsfB
Docking and fuel transfer complete! Valentina now has the center seat, ready to set course for Duna! #KSP https://t.co/QDzSZ4kZHS
EveLander2 was almost refueled but the small ship used to transfer the fuel also ran out off propellant. Also, it's not easy to keep two non maneuverable ships from drifting apart. Sending the last tank of fuel directly. It's becoming an expensive mission #KSP https://t.co/3ia9DjLS4z
The engineering team at the Rockomax Conglomerate decided to revamp the RE-L10 “Poodle” Liquid Fuel Engine and turned it into a dual combustion chamber closed cycle engine that will continue to excel at landings, orbital insertions and transfers. Do you like it? 🚀#KSP #Preview https://t.co/VLmFTaJVha
Au revoir ATV! ESA's Automated Transfer Vehicle, carried into orbit by the Ariane 5 launcher, carried supplies and fuel during the course of 5 missions. Program ended on February 2015. #KSP #ESA #atv https://t.co/7zPfcLXhz6
DE I after achieving orbit around Kerbin. Plenty of fuel left for the transfer! The top part lands on Duna. #KSP http://t.co/uwEJeWwAOc
McCandless Station is complete! At some point today, she will see her first shuttle visit from the Dynawing orbiter, to test her abilities to transfer fuel and crew. #KSP https://t.co/BA0J1falfN
Today I performed a training flight of OKM-7A7 "Burya" spaceplane with 50 tons of payload. 🚀 Lunar Transfer Vehicle needs a lot of fuel, so I'm trying to increase "Burya"s payload up to the limit! Orbital flight will be happened ASAP! #KSP #SSTO #games #space https://t.co/tyirHOjLOz
UB-R Space's Minmus Fuel and transfer station is operational. #ksp http://t.co/WXirgo4EqJ
Uhh! Today I've perform the first orbital flight of a new version of "Burya" (OKM-7A8T) with a huge payload of 87 tons of Lf+Ox+Mp. 🚀 With such amount of fuel delivered by one tanker, simple usage of LTVs (Lunar Transfer Vehicles) became possible! 🌔 #KSP #SSTO #space #games https://t.co/kjjgubwHyC
ksp fuel transfer Q&A Review
How accurate is Kerbal Space Program to real life?
Since the version 1.0, there is no major flaw in physic that would look ridiculously wrong. They managed to make a believable, educational and highly enjoyable space simulation. When you look at the detail, they are inaccuracies everywhere., But there are good reasons for them, as I'll explain bellow, mainly due to ,gameplay,, or ,computers' limit,, and I am glad to see there has never been "things left behind because we were lazy" and that there is no more "things left behind because we are working on something else" ; every flaw of the physic makes sense gameplay wise. A quick glance at ,Realism Overhaul,, a collection of mods designed to improve realism, gives you tons of information of what is wrong in KSP. Inaccuracies and omissions that serves gameplay When you make a game where the player makes the job of thousands of people, you have to commit on realism to make the game a game, enjoyed by a large public. Here is a non exhaustive list of omissions and inaccuracies that serves playability : Scale size :, KSP is 6.4 to 10 times smaller than real life, depending what you are looking to. ,That way, a typical KSP launch is 2 mins long instead of the 10 mins long real life launch., Methinks, this is the greatest inaccuracy, because, for balance and entertainment purpose, it leads to a huge set of inaccuracies and misconceptions : the Kerbal System is so small than real life rocketry would destroy any challenge (eg, there would be no point to stage). The game developers have found a balance were brute force and silliness (like vertical ascent to the Mun) is not punished, yet clever thought and realistic designs are rewarded. Consequent inaccuracies include : Efficient engines :, chemical engines in KSP have an incredibly high efficiency, only matched by our hydrolox engines, but those have drawbacks KSP engines haven't (like lower Thrust to Weight Ratio). Heavy hulls :, empty fuel tanks and engines are by far heavier than their real life counter part. It makes up for the efficient engines and go a bit further. With normal hull and lower efficiency, the size of both rockets and interplanetary ship would have been ok, but there would have been no point to stage. The 1:9 dry ratio of a fuel tank is absurdly high ,to encourage staging,, and efficiency had to been raised to keep balance. Denser fuel, : I am not sure about it, but I'd bet it is to have a nice looking rocket at KSP size scale despite the heavy dry tanks. Circularisation waiting time :, I already mentioned a real life launch is 10 mins long, but it also is 10 min of acceleration, while in KSP, the easiest designs to come up with include a "wait to circularize" time in the launch process. It is possible to do so in KSP, but far easier with a fully grown Earth where you can go mainly horizontally yet still having 5 minutes before apoapsis. Incidentally, KSP rockets generally need higher Thrust to Weight Ratio for their last stage. Life support :, There is none in KSP. Communication :, There are a lot of things that are not addressed in KSP concerning communication. Basically, you put your hand-made radio antenna on your vessel and you instantly communicate back to KSC through the whole system. Network :, In real life, we can communicate through space with a network of satellites, each having direct line of view to their neighbor, often with dishes antenna than can only look for one direction. Delay, : Even in the small Kerbal system, light takes minutes to travel. Executing orbital manoeuver is no big deal, but operating a rover on Mars is something totally different, and that is partly why rovers only cover some few meters a day. Apollo 11 has been tested without a crew, but the Moon landing was a first time, simply because we had nothing but human to pilot the lander (no computers) and earth is to distant to perform the landing from there. Electricity :, Ksp has its own electricity system, and include quadratic reduction of solar flux, which is both realistic and interesting game wise. As far as I understand, generators are too powerful, solar panels too heavy, and end game consumers too greedy. Control : ,KSP accomplishes the (unrealistic) wonder to let amateur to drive poorly designed planes with a mouse and a keyboard. Stability ,: reaction wheels are way to much powerful, for two reasons : it helps making stable craft without painfully tuning weight balance and aerodynamic, and it helps rotating your space station within 60 seconds, while the ISS would take a whole day. Control binding :, KSP is really marvelous on this one : you build a craft and it guesses how you are supposed to drive it, what thrusters are used to pitch, yaw or roll... The counterpart is that specialized vehicle, like hoovers, are hard to do with only action groups. Structural resistance, : KSP material are very sturdy, especially wings. Not too much so that things still break, but far less often than in real life, so that very little attention is required to it. The most ludicrous example are kerbals themselves, enduring up to 50 m/s (180 km/h) shock only to bounce without a scratch. Weather :, another (deliberate) omission. Aerodynamic and overheating :, They are present in the game, but a bit easier/simpler than IRL. Given Kerbin’s size (therefore velocity needed to establish orbit) and Kerbin’s atmosphere size (nearly as big as Earth's), drag loss is more a problem and overheating is barely one, even on reentry, while in most of the case, Real Life drag loss are negligible and overheating a mind blower. It is not as ludicrous as before, but in KSP, you make a gravity turn instead of burning directly horizontally mainly to avoid insane drag, while in real life (at least with realism overhaul), you do it mainly to avoid disintegration. Fuel type :, In real life, there are numerous kind of fuel, specific to each engine, but also specific tank to contain them, pressurize them and ignite them. Some fuels are prone to leak out while exposed to the void space. Fuel flow :, From a realistic perspective, the cheap yellow fuel line is very laughable. Fuel flow inside a tank is already a major problem to solve building actual rockets, transferring from a tank to another requires an expansive and complex pump. Add that to heavy hulls and the aspargus staging became unrealistically easy and advantageous. Solid Booster, engine ignition and throttle :, In real life, solid boosters are not the only one to be "unthrottlable", and we have more control on their thrust over time than many liquid engines (by shaping them). Most rocket engines aren't. By default they aren't, because it adds complexity to the design, and complexity equates chances of failure (and cost). Only last stage, some interplanetary or landing engines have the ability to throttle or to ignite several time (which is yet another thing). logistic :, KSP is not an economic simulator, so the career part is more milestone to progressively discover possibility or set challenges than something accurate Cost :, Kerbal space program has it wrong that a rocket's cost is the sum of the cost of its part. The real cost is to develop new part (symbolically here in KSP), to design a rocket and to actually glue the parts together (completely absent). Recovery :, There is no such thing as a 100% or even 90% price recovery. IRL, we have yet to design a space craft that can, after coming back from orbital speed, be reused within the week, let alone be competitive with non reusable launch systems. There are no maintenance/repair cost in KSP, wheras IRL, this is precisely what makes the space shuttle so expansive. Time :, Rockets take time to build, and technology to be developed. In KSP, it is possible to complete the tech tree within 30 days or even less, and the VAB can continuously spit out kilo tons of rockets. Attrition :, Space is a rough place to be and everything dies out or randomly fails at some point, at least from sublimation, if not for solar radiation or corrosive atmosphere of other planet. Much more things I can't think of Almost any of this inaccuracies or omissions have been addressed by mods, and realism overhaul has keep the few that makes it looks realistic and bring challenge, from "let's launch a rocket, see where we can go and do science!" to "let us meticulously plan each part of our trip and design our rocket accordingly, and wait tenth of failed tests to finally grin as you achieve your goal". Inaccuracies and omission because of hardware limit When you make a game for home computer where you can simulate years in minutes while displaying a fancy 3d interface, you simply cannot hope to be as accurate as the beasts I bet space agencies have. And RL orbital mechanics do need these beasts. Here is a non exhaustive list of inaccuracies and omission that are (mainly) due to the limited power of computer. Orbital mechanic :, KSP solely rely on a 2-body approximation because it has some nice closed formed solution (it is not necessary to compute steps by steps), with the following inaccuracies : No n-body mechanic, ,that is : planet are on rail, and not influenced by others, for ships : no Lagrange points and no interplanetary transportation network. Ponctual ships:, I am not sure about this one, but I think every part of the vessel are subject to the same gravity (those who would apply to the vessel's center of mass), so no tidal locking. Ponctual planets :, The gravity field of the planet is the same as if the planet was perfectly round (or a point, it's the same). For example, planets not perfectly round allow ,Sun-synchronous_orbit Atmosphere :, Aerodynamic is very greedy on CPU Size and orbital decay :, The atmosphere cuts off "sharply". It may not be sharp for the player that barely lowered his periapsis under the atmosphere and must watch its craft slowing for hours to land, but right passed the KSP atmosphere limit, a craft would not last a month, time scale that also intervenes in KSP Focus :, Physic, including atmospheric mechanics are only applied to the ship focused on and the ones within 2.5 km or so (it may have increased since I last checked), otherwise, the ship either disappears or goes on as if it were in the empty space, depending on its altitude. It is particularly annoying when you want to launch a rocket from a plane and recover the plane. Number of celestial objects :, You can only track a bunch of asteroids at a time, and having proper rings or asteroids' belt with asteroids defined individually is inconceivable. Mods have tried their best at them, but the computers set an hard limit where you can not do resource greedy calculations on many objects at a time. Inaccuracies that are there for technical reasons Or things that are not absolutely necessary but I think it's a shame KSP has not them, and that are discarded for technical reasons rather than gameplay choice or hardware limitations. Rotation :, Time warping kills rotation. It is quite convenient, but it would be fun it does not, and honestly, constant rotation is far simpler than 2-body mechanic. Axial tilt, : in KSP, every single planet rotates around the same damn axis, which cuts off a great and interesting part of rocket science. It is really a pain for modders working on Realism Overhaul. Sadly, no mods for this ones, they are hard coded in the game. Making an orbital simulation that include them is darn easy (the maths behind tilts and rotation are far easier than those behind Keplerian orbit and can be added independently), but Squad did not incorporate them since the beginning, and it would be a pain to add them now, especially tilts. So you got My point, KSP is far from accurate, and I have stuck to things I can conceive. It is a necessary over simplification. But since the aerodynamics is fixed, it does not teach anything wrong. In addition to making patched conics intuitive, it also generates curiosity and leads me to search more about rocket science, whether it's in the game or not, and I think this is more valuable than realism.
Is the "Kerbal Space Program" PC game a good way to teach people about rocket science?
The game won’t necessarily land you a job at NASA. But Kerbal Space Program (KSP) really helps the ordinary geeks among us gain a far greater understanding of ,why, things are what they are in spaceflight. Let me give you my favorite example. In the real world, getting to the planet ,Mercury ,is so difficult that we’ve only sent two probes there, with one on the way. The problem is that it takes far, far more energy to slow down enough to reach Mercury (orbiting or not) without a lot of work. Now, KSP allows you to tackle a similar dilemma with its counterpart to Mercury, the planet ,Moho,. The game’s rocket technology is a bit advanced and overpowered than what we have here, and the game’s worlds are scaled down. So you could design a spacecraft that can reach Moho by a direct ,Hohmann transfer,. But you will burn far more fuel to brake into Moho’s orbit than the rocket you used to launch your spacecraft in Kerbin orbit in the first place. ,(Kerbin is the Earth-like home of the little green men and women who are just starting to explore their solar system, which is similar to our own.) And good luck having enough fuel needed to return home to Kerbin, much less land and return from its surface. In the real world, we simply can’t send a probe to Mercury directly that way. This is why the three Mercury probes (,Mariner 10,, ,MESSENGER,, and ,BepiColombo,) used or will use ,repeated gravity assists of Earth, Venus and Mercury itself, which not only slow down the spacecraft as the Sun’s gravity forces it to accelerate, but make important adjustments that change your spacecraft’s inclination so that it matches Mercury’s to save more fuel. BepiColombo’s flight path, below, shows a similar path to what I’m trying to do in my current KSP game. Like the three real-world probes, I launch from my home world and then aim for making a gravity-braking flyby of the Venus counterpart planet of Eve, which will eventually give me my first Moho flyby. At the Moho flyby point, I will make small corrections in combination with Moho’s gravity braking ability to slow me down, lowering my orbital height and adjusting my orbital inclination. In the screenshot above, my probe is in its final pass before trying to attain orbit of Moho, after using an Eve gravity brake some time before. It’s already made one Moho pass, preparing for a second, which will lower the orbit and speed enough to make a significant fuel savings in attaining the innermost orbit line. An important note is that I, the player, am using the game’s interface to make these maneuvers manually. There are add-ins, or mods, which can do these calculations automatically. But you’ll learn much more about why things work by doing it yourself. KSP allows you to accelerate time, which is important in my example. Like the BepiColombo animation, you have to wait for the right time in KSP to make the small course corrections to make your flyby gravity brakes as the planet and your spacecraft align for another pass. As I don’t have years in the real-world to wait as the European Space Agency or NASA have to do, so I set a maneuver, then accelerate game time to reach the next burn. KSP also teaches the fundamentals of orbital mechanics, rendezvous, delta-V (change in velocity, based on your fuel, spacecraft weight and rocket engine thrust), landing on a world, with a little design needs, such as center-of-mass, center-of-lift and the like, thrown in. You can go very overboard with a rocket or spacecraft that can’t possibly exist in the real world. But, as in my example, KSP also allows you, if you choose, to emulate real-world missions with similar limitations on fuel.
How much DeltaV did the Apollo CSM have docked with the L.M. and undocked?
It’s bad enough that I’m playing Kerbal Space Program obsessively, learning all about ,delta-V,—the change in a spacecraft’s velocity necessary to reach orbit and/or leave a planet or moon, be captured by another body’s gravity, land, or return and leave orbit. And now, your question triggers my KSP OCD, combined with my love of space history. I ,love ,this stuff. With my improved understanding of orbital mechanics, my Google-fu is sufficiently primed. So NASA, being NASA, made a graph in 1966 that illustrates the answer. Each light-shaded (not solid) bar, from left to right, denotes the delta-V required for each (literal) stage of the mission. The Saturn V moon rocket first, second and third stages chewed up over 5.6 million pounds of propellant to get the S-IVB third stage into Earth orbit. Then, for trans-lunar injection, the S-IVB burns later to push the Apollo spacecraft away at escape velocity (about 25,000 miles per hour, or 11176 meters/second). The graph uses Imperial measurements in feet per second so I will make rough conversions as many of you are doing the metric system as most humans use. (Hopefully I’m interpreting the right bars correctly and my numbers aren’t too far off. Any of you real rocket scientists can feel quite free to correct me in the comments.) Since you asked only about the Apollo Command/Service Module, let’s jump to it. The CSM was loaded with about 9,199 ft/sec (2804 m/sec) delta-V. During lunar orbit insertion, it would use around 3,800 feet/sec (1158 m/s) delta-V to achieve an orbit. After lunar orbit rendezvous with the Lunar Module ascent stage, crew transfer and jettison of the LM, the CSM would use around 2,500 ft/sec (762 m/s) to escape the Moon to return to Earth. I do recall that the extended-stay Apollo J-missions used a bit of the spare delta-V of the CSM to bring the LM to a lower orbit to save more of the lander’s Descent Stage fuel. This graph doesn’t note that as an older H-mission chart, so perhaps somebody else can inform us what that might be. I would think that the CSM would then re-circularize its lunar orbit after LM separation for descent. Those with better math skills than I might then note how much delta-V is left over in the Service Module by the time a Command Module nears re-entry and jettisons that propulsion module. It’s around 2,899 ft/sec (884 m/s). Those KSP players are going, “Why so much fuel left? That’s extra weight that could’ve saved fuel later on for the landing.” Perhaps. But there’s another reason why there’s about a quarter-tank of spare fuel: ,A direct abort. If something very critical failed in the spacecraft after the trans-lunar coast started that wasn’t associated to the Service Propulsion System (SPS)—something that would eventually or immediately endanger the astronauts (including a serious medical condition), a direct-abort burn would be done. It would take about 1853 m/s (6,079 ft/sec) delta-V to do this. Depending on the scenario, the burn could use only the SPS, the Lunar Module’s Descent Propulsion System engine, or both, based on decisions from Mission Control. As the chart shows above, a direct-abort burn could be immediate or conserve fuel. ,You can read more about Apollo’s abort planning in this NASA document. As fans of the ,Apollo 13, film may recall, a direct-abort was considered but the character of Gene Kranz dismissed it, given that Mission Control and the astronauts had no idea what damage that destroyed an oxygen and the spacecraft’s main power may had done to the SPS. Igniting the SPS could’ve caused the SM to explode or collapse. In the real-life mission, the option for direct-abort wasn’t viable because a time-critical direct-abort would require ,jettisoning the LM,—which, as you may recall, was the only option for life support as the fuel cells and SM oxygen starved out. The LM’s DPS alone hadn’t sufficient delta-V to make a direct-abort, even if the SM was jettisoned. And making the most desperate direct-abort—jettisoning the SM, burning the DPS to depletion, then jettisoning the LM Descent Module to use the Ascent Propulsion System engine in the Ascent Module—it was too much risk that would leave only hours of life support and limited battery power in the LM Ascent Stage (jettisoning the Descent Stage would lose 5 of the spacecraft’s 7 batteries). All that is assuming that the total delta-V in the LM could make a direct-abort. I don’t think it could. Using the LM as a lifeboat, returning the CSM/LM to a free-return trajectory to loop around the Moon with the LM’s limited delta-V was the safer move. And now I need to prepare to make a landing of a crewed Kerbal rover on the Mun. Wish me luck—although I loaded that rover with enough delta-V to land itself twice.
What is the most impressive thing you have built in Kerbal Space Program?
I am most proud of a Kerbaled return mission to Eve. It involved six different spacecraft, three of which were fuel tankers. But what I am most proud was the orbit return lander, which was one of my most satisfying designs ever. Here it is. It’s beautiful because the constraints of an Eve return launch necessitated me to ruthlessly cut any excess. My first prototypes were more than one hundred tons ; This baby was cut down to roughly 20. Still, back in those days launching it wasn’t easy. Here it is sitting pretty on the launch pad: It also required another launch to dock itself to a transfer stage that would actually send it to Eve! Nevertheless, I was super-proud of it. Sure, it required a mod - the hexagonal attachments were aerostatic parachutes (baloons, esssentially) that made the mission possible, but I ,still, had to cut the thing down to the bare essentials. It was ,just barely, enough to lift two Kerbalnauts up to low orbit…strapped to the final stage’s fuel tanks, in their exterior seats. That is how they looked after the ride back to orbit: The orbiting Kerbin return vehicle went to pick them up later. Nowadays it would be virtually guaranteed fatal, since I tend to play with life support mods, but back then it was a glorious way to save a lot of mass. The mission also involved horrifying torture of a Kerbal. See, that return vehicle was inserted into orbit via aerobraking. That required its solar panels to be retracted. After the aerobraking phase was done, I switched to the crewed lander/rover (another wonderful invention of mine) and forgot to extend the panels. The lander ran out of juice and was stuck in orbit. So…I made this, and sent a single Kerbal on a lonely journey through the eternal void. ,In nothing but his spacesuit. 105 days ,in space. Alone. Strapped to a nuclear-powered rocket. In a spacesuit. He wasn’t happy. But in the end, he did his job, extended the closed panel and enabled his comrades to return from the surface and back to Kerbin for their ticker-tape parade, and his therapy. The trials and tribulations of this mission, coupled with the need to strain my thinking muscle just to come up with the hardware for it, made it my proudest moment in KSP to date. I did more complex flights since then, built huge space stations and sent nuclear-powered jets to Laythe, but I remember this one with the most fondness of all.
How hard is Kerbal Space Program?
That really depends on the player, and not just the player’s ability to pick up concepts and such. KSP, even in “career mode,” which is not a campaign regardless of what some people think, is a sandbox type game. The goals are entirely your own. I’ve seen players that perform wildly complex and precise missions with tons of pre-planning, I’ve seen people that will gladly send overkill amounts of hardware and fuel on every mission, and I’ve even seen a few that go hundreds of hours not even leaving low Kerbin orbit. I’d say that there are further players that don’t even leave the atmosphere for long lengths of time, but truth be told, aerodynamic flight is more complicated than rocketry in KSP, and I’m pretty sure that in at least some aspects that’s true in reality as well. Getting to orbit is one of the easiest things to do in the game, and there are people that have issues with that at least at first. Docking in orbit is actually one of the harder things to do until you get used to it, at which point it becomes easy. Efficiently transferring to a different planet can be hard at first, but is pretty easy if you brute force it. One of my first attempts to go to Eeloo, the farthest planet out in the stock game, took centuries because I kept missing. Some parts of rocketry or orbital mechanics can be counter-intuitive. For example, rockets tend to be more maneuverable if they’re top heavy. If your rocket wants to flip over during ascent, that’s because it’s bottom heavy, not top heavy. Or orbital rendezvous, where some times in order to catch up with something ahead of you, you need to slow down. So in general, the difficulty in KSP usually isn’t in doing something, it’s in doing something efficiently. KSP players will tend to start to have a gut feel for orbital mechanics even if they don’t study the math behind orbital mechanics. There are far more KSP players that understand the basic implications of the ,Oberth effect - Wikipedia, than can explain what causes it or do the math to show how much it will affect the mission. However, once you get to the point you can do most things efficiently, you can up your challenge a few different ways. First, if you’re playing in sandbox mode, where you start with all parts unlocked and have no budget, you can try science or career mode. Science mode means you have to earn science points in order to buy access to parts. Career mode goes one step further, where you pick up contracts that pay you funds when completed, at which point you not only have to unlock the parts with science, you have to purchase the parts themselves with funds. Personally, I was playing KSP long before science or career mode was added, so there’s no challenge in playing sandbox mode to me, so I haven’t used sandbox mode to do anything other than familiarize myself with new parts since science mode came out. Likewise, once career mode came out, I started playing that mode just about exclusively. Once you’re playing career mode and it’s providing little to no challenge, you can reduce the rewards so that it’s harder to unlock parts or earn credits to buy parts. In other directions, not exclusive with sandbox/science/career mode, there are mods that can increase the difficulty. Stock KSP doesn’t deal with life support, so there are multiple life support mods, depending on the type of challenge you’re looking for. These range from simple consumables to more advanced consumables to recycling consumables to making sure that you have enough room for the kerbals not to suffer from cabin fever to dealing with radiation issues. Other types of mods add other complications of reality, like different fuel types, cryogenic fuel boil off, limited re-ignition engines, etc. Other types of mods you can add to increase difficulty increase the scale of the planets. RSS is a mod that replaces the Kerbin system with the Sol system, and even goes so far as to have you launching from Cape Canaveral rather than some place conveniently located very close to the equator. So really, like so many other parts of KSP, the difficulty itself is largely up to the player.
What is the difference in fuel required to launch a rocket from the surface of the moon to Mars, compared to launching from Earth?
Ah, once again, experience in KSP comes in handy. Launching from the Moon’s surface, then departing lunar orbit similar to a return to Earth, but with a periapsis high enough that the craft doesn’t encounter significant aerodynamic drag, then doing the transfer burn at periapsis, would have one major advantage and at least two disadvantages. NOTE: It would probably make more sense to launch from lunar orbit, and use other craft to ferry the fuel from the Moon’s surface up, that way your “transfer craft” doesn’t have to be capable of landing. The advantage would be that for the cost of reaching lunar escape velocity, you hit your Earth periapsis approaching Earth escape velocity, and that is a HUGE difference. We’re talking a quarter the delta-v. So yes, done right, the fuel savings from the point of “final” launch can be huge. The disadvantages? It only makes sense if you’re manufacturing fuel on the Moon. If you’re not doing that, then the effort of getting all of that to the Moon is going to eclipse what you saved. And if you’re only manufacturing the fuel there, then you’re still going to have to spend quite a bit of delta-v getting the rest of the rocket there, you just get to top off. And some types of fuel won’t be easy to manufacture on the Moon. In fact, I’d go so far as to say that none of them will be “easy,” they’ll just be more practical. They will probably require large amounts of electricity to create, and probably more to refrigerate, since many of them need to be kept at cryogenic temperatures in order to not take up too much volume. The other disadvantage is that your transfer burn needs to happen in a fairly specific location, not just anywhere in low Earth orbit, so you need the Moon to be in the right position when your transfer window opens up. This generally means that you won’t be hitting the most optimal point of the transfer window, but the difference shouldn’t be as much as you’re saving. While it’s all doable, even in the simplified environment of KSP, it isn’t particularly practical unless you either already have the refueling infrastructure set up or are sending a particularly large mission somewhere.
Hey, I just started playing KSP 2 weeks ago, and I'm having trouble doing a rendezvous, any tips or advice on how to do that?
Welcome to KSP! I’ve found this an easy yet difficult game, and if you play it the right way, very enjoyable and you will find that you learn a lot. Let’s get some background behind orbital rendezvous, and then I’ll share some good tips for doing a good rendezvous. Orbital mechanics are a case of spherical geometry, in that much like a car can be defined as being on a specific road with a specific velocity, an orbit can be defined by a specific number of unique values. KSP simplifies this to a point, in that several values are ignored. In KSP, an orbit is defined by the apoapsis (the highest point in the orbit), periapsis (lowest point), inclination (the angle between the orbit plane and the planet’s reference frame formed by the equator), the ejection angle (defined as the angle between the object and the parent body’s orbit vector, the Longitude of the Ascending Node (basically defines the points where the object’s orbit passes over the equator), the Argument of Periapsis (the angle between the previous point and the periapsis), and finally, the eccentricity, which basically is the difference between the orbit and a perfect circle (an orbit with an eccentricity of zero is a perfect circle). I would assume that a fair few just skimmed over that last paragraph once it became clear that it was a list of definitions, here is a picture that shows a lot of them The reason for listing out all of these definitions is that a particular orbit will have a unique value for each of these, and in order to successfully rendezvous with an object in orbit, your controlled craft will need to match all of these. Maneuver planning can be quite complicated in real life, however, to make this a lot more accessible to more people, KSP has a graphical interface and a simplified maneuver node. Let’s take a look at that. A maneuver node is defined as a three dimensional vector, in that a change in velocity is assigned in each axis in cartesian coordinates, that is, x, y, and z, shown in this image as normal, antinormal, prograde, retrograde, radial in, and radial out. These are also among the presets for the SAS system. KSP will calculate the results of any burn in real time given the inputs for this maneuver. To understand how to use the maneuver mode, let’s examine each of these. A burn prograde will increase the velocity at the point of the burn, raising the apoapsis and lowering the velocity at that point. The reverse is true for burning retrograde, in that it decreases velocity at the point of the burn, lowering the periapsis. Burning normal and anti-normal is used to change the inclination, however, as this also increases the velocity of the control craft, this also raises the apoapsis similarly to burning prograde. Burning radial in and radial out has some interesting effects on the orbit. These effect the control craft’s radial speed without changing orbital speed. If you burn radial out, this has the effect of raising the apoapsis since you are increasing your radial velocity, and since the orbital speed doesn’t change, the periapsis is lowered at the same time. The reverse is true of burning radial in. A combination of these are used to achieve a rendezvous with an object in orbit. As an example, let’s use this model of the International Space Station as the rendezvous target, set at an altitude of just under 139 kilometers, at an inclination of 35 degrees. We’ll use this craft as the control craft to show rendezvous with the ISS in orbit. To reduce fuel use , you will want to match the orbital plane of the target object. For a target in an equatorial orbit over Kerbin, you can launch whenever you want, since the KSC in the game is on the equator. In this case, we have to wait until the orbit of the target passes just ahead of the launch site. To really reduce the amount of time it takes to dock with the station, you could launch at a time when once you reach the target altitude, the target is there and you can reduce speed and dock, however, this is somewhat difficult to achieve by eyeballing, so what we will do is launch into an orbit which has the same parameters as the target except that we will be at a lower altitude. Launch site not in right place There we go, now we can launch,. Another bonus of this is that the heading for the launch is simply the inclination angle, 35 degrees, from the equator, in this case 125 degrees from true north. Now that the vehicle has reached orbit, I can explain a bit more. I delayed a little too much in launching, which means that there is slight differences between the control craft orbit and the target. This means that I will need to change my orbital plane to match that of the ISS. This is where the two points marked AN and DN come in. These are called Ascending and Descending Nodes, and mark the points at which the control craft’s orbit passes through the target orbit plane. A burn in Normal or Anti-normal at these points will serve to match the orbital planes. This makes rendezvous a two dimensional problem instead of a three dimensional problem. Instead of worrying about numbers, just put the target orbit in this view, so that it looks like a single yellow line, and manipulate the normal and anti-normal velocity changes until the dotted line matches. Alright, we’ve matched orbital planes. However, there is a mistake that I made back at the launch step that may be noticeable. The control craft is the one further to the right, just over the DN marker. The ISS is further behind, higher in the image and to the left. What this means, is that there will be a delay in reaching the target. What you want is to launch below the target’s altitude and behind in the orbit, that way you can transfer to the target orbit easily. This is very similar to a transfer orbit from Kerbin to a planet at a higher orbital altitude, such as Duna, or a transfer orbit to either of Kerbin’s moons. Now that we are behind the ISS in its orbit, we can now plan the approach. We’ll just create a maneuver, raise the apoapsis to match that of the ISS, and then we can play around with the time of the burn to achieve a close approach, this is where having the same orbital plane as the target is helpful. If you raise the apoapsis to just the right altitude, you will see a single pair of arrows. This marks the locations of the control craft and the target at closest approach. In this case, what this shows is that we waited too long, and once we get to the target altitude, we’ll be ahead of the target. If you raise the apoapsis higher, you’ll see two pairs of arrows in orange and purple. This shows the locations of the control craft and the target at the first and second time of closest approach. This may be helpful in certain cases. To get a closer approach, I played around with the time of the burn, as well as the change in velocity in each axis. Also be sure to take advantage of the newer approach tools in the lower left hand corner. This shows the details for each closest approach on the left. The right hand side is a similar interface to that of the node itself, where you can change the velocity in each axis, and change the sensitivity of the alteration with the scroll option next to it. I managed to get the closest approach to about 200 meters, however, to make this a bit closer to what happens in reality, I set the closest approach to just over 1 km (in real life, rendezvous and docking with the ISS is done in stages, with craft getting to 20 km behind and holding, and then steadily approaching, with checkpoints in order to ensure the safety of the station). What’s also helpful with this approach is that in this case, the closest approach occurred in Kerbin’s shadow, which can hamper visibility and make the docking a little difficult. Also bear in mind that I am using a craft with RCS fuel and thrusters. While docking can be done without RCS, I prefer using RCS as it makes it more realistic and easier, especially when docking with something that doesn’t rotate easily. For the next step, we’ll use the RCS thrusters to point our prograde marker in the same direction as the target, this is using the Target setting on the HUD. I would advise not approaching at a fast speed, try for something between 1 and 2 m/s. This will require a watchful eye, as even this close, the orbits aren’t exact, and the prograde marker will tend to drift. Next we will need to determine an exact docking port to target. Here I have set the control craft to hold at about 1 meter and have selected a docking point. This is done by right clicking a docking port and selecting “Set as Target”. From this image, you can see that we are above and to the right of the axis running through the docking port. To make it simpler, we’ll use the techniques that are used for actual docking in order to make this less complicated. Off-axis docking in KSP can work, but often results in collisions, as well as for smaller target craft to start spinning, which is frustrating. This is also why I like to have RCS thrusters, as it makes this problem simpler. We align with the docking port by first eliminating the distance in one axis and then in another We are now on the axis of the docking port, and the rendezvous has been reduced to a single dimension, and is only a matter of distance and approach velocity, which should still be slow. This allows for a smooth and accurate docking, exactly where you want to go. In summary, here are some of the tips that were dispersed within that example. Launch in the same orbital plane as the target, if you are taking off from the surface. If you are attempting to rendezvous after a transfer to another object, attempt to insert your vehicle into the same orbital plane. Perform orbital plane changes at the AN and DN points, this will minimize the effects on the rest of the orbit. Always reduce the number of dimensions. Achieve the same orbital plane, to make the transfer to target orbit easier. Get onto the axis of the docking point you want to dock with at a fair distance from the target, which also makes docking simpler. Have RCS on your craft if possible. This allows for much smaller velocity changes than the main engine. Plan on needing a little extra fuel (My first example target craft didn’t have enough fuel to reach orbit, an oversight on my part.) Plan out everything. My example follows a pretty good procedure on docking with a craft in orbit. This will lower the potential for mistakes, even though that’s what F5 and F9 are for (quicksave and quickload). Don’t rush through anything. There is a reason why rendezvous and docking in actual space missions take forever. This is particularly important in KSP, as being impatient is both going too fast and using too high a time warp. Missing a critical event can be both annoying and dangerous, as you could accidentally collide with something important. Don’t be afraid of making mistakes. The number of times I’ve messed this up. . . Have fun and play around with it. KSP is known for its explosions for a reason. Hopefully this helps. I’m serious on that last tip, have fun with this, play around with things. Next thing you know, you’ll be constructing a massive station in a polar orbit around Laythe using an SSTO (I’m serious, the sky is not the limit in this game.)
Is this delta-V subway map accurate? And how do I relate it to payload mass?
This map is accurate. For your first question, you still might want to learn about ,Launch window, : in space, if you plan to go to a place, may it be a planet or near an other space craft, you not only have to go to the right place, you have to be there at the right time. They are called launch windows because in real life, as all spacecraft are Earth-born, they mostly dictates the time of an actual launch, but many KSP player (myself included) often refer to them as ,transfer window,s, because more than launching a rocket, you want to travel, and travelling in space means transferring oneself from an orbit to another orbit (for example, if you sent a crewed craft in Moon’s orbit, there is a transfer window during which it should do its return burn, if you want to efficiently bring it back earth). Later, I’ll dig into details as for how this map has been obtained, and how to create your own in your custom stellar system, and how to add object like artificial space stations… But for now, let’s jump to your second question : how to use it? If you want to go from Earth to Neptune, follow the line that link them and add the delta-v you encounter : this is the delta-v budget of this mission, the cost of such trip. If the space craft can resist the atmospheric pressure, you can skip or at least cut greatly (skipp for now, and compute the landing/ aero braking cost when you’ll want more precision) the parts of the trip with a white arrow in the direction you are heading. If he can’t, he cannot ,land, whenever there is an atmosphere… An important note is that this map is Earth centred and can only be used for Earth-X or X-Earth trips. Now, to know how far, regarding delta-v, a spaceship can go, use this : \Delta v = v_e \ln{\frac{m_0}{m_f}} This is the ,Tsiolkovsky rocket equation,. It comes from the fact that in order to accelerate in vacuum, you have to throw something in the opposite direction (at speed ,v_e,), and that the reaction mass you throw away for accelerating yourself also have to push the reaction mass you carry for later use. That is why the mass ratio between your initial mass ,m_0, and the final mass ,m_f, goes exponentially worse with the speed change ,\Delta v, you want to achieve. It is extremely similar to the famous problem of the camel and the bananas : ,A camel transporting bananas,. The exhaust velocity ,v_e, is the part that depends on the characteristics of the (reaction) engine you use. Here are several specific ways to use this equation. For example, for each craft, you can store their dry mass, their tank capacity and the exhaust velocity of their engine Doing a manoeuvre/trip, you can plug its cost into the ,\Delta v, of the equation, and ,m_0, and ,v_e, from the craft, the former being the total mass (dry + fuel + payload, if any), to deduce the final mass ,m_f, (dry + remaining fuel + payload) and deduce the remaining fuel. Compute and display the available delta-v of a craft, plugging its ,v_e,, its initial mass (again, dry + fuel + payload) as ,m_0,, and the final mass (dry + payload) as ,m_f,. That way, it allows player to know whether some trip is possible or not. For refuelling purpose or spacecraft designing : given a space craft exhaust velocity, its mass along with those of a payload (the sum of these two is ,m_f,), and the delta-v budget of a mission, compute the total mass required (,m_0,), or equivalently, the mass of fuel (,m_0 - m_f,). Still for spacecraft designing : given a spaceship dry and wet mass, and a delta-v budget, compute the maximum payload. If we call ,m_p, the payload mass, we have to plug ,m_0 = m_{wet} + m_p, and ,m_f = m_{dry} + m_p, and inverting the equation to express ,m_p, (in bold because I think it was your question). I have supposed that the spacecrafts we talk about only burn fuel, but current space craft do leave their empty tanks and their engine behind as they get lighter, because dead-weight is awful in space. You can cut the spacecraft’s DV computing into steps, corresponding to its stage. If you only drop identical empty tanks, you can also computing an equivalent pseudo exhaust velocity (eg if ,v_e = 100,, an empty tank weights ,1t, and hold ,9t, of reaction mass, after emptying the tank, you throw 9t at speed 100 and one at speed 0, which is almost the same as if you threw 10t at speed 90. This reasoning is slightly flawed because the empty tank is dropped after the reaction mass, and had to be pushed, but reasoning directly on the Tsiolkovsky’s equation works) I imagine the two last point more for an design assistant, than for a completely automated spaceship designer (that an AI could use for example). The former does not need to make accurate prediction, as they can be corrected by the first point, while the later needs an accurate prediction and needs to take into accounts the facts that bigger (empty) fuel tanks are heavier, and that heavier crafts need heavier engines. If it is linearly heavier, it can be reasonably (explicitly) handled, but in reality, it isn’t (bigger is better. eg. : a spherical tank, mass rising as the surface, the square of the radius, fuel capacity as the volume, radius cubed). As my answer is already long, I will throw some brief points that I think are worth mentioning, trying (and possibly failing) to make it short, so you can ask about them if needed. I haven’t dug into details on how to build such a map, but understanding Hohmann transfer is all you need to understand to build such a mas for weightless bodies. Understanding ,Patched conic approximation,, lets you produce this map with massive bodies taking account of the Oberth effect. Each node of the represents a position, that is, either an orbit, or a planet on which to land/crash. The map is Earth centred, and the label Earth intercept does not means the same thing as intercept for other planets : the first corresponds to a circular orbit around the Sun similar to those of Earth but out of Earth sphere of influence, the later is the elliptical orbit that links the Earth orbit to another. The following map is more verbose. With this map, when you go into an orbit, with good timing, you can rendez-vous with anything (station, ship..) on that orbit. If you need to keep track of the remaining fuel at any time, you have to fully understand to what orbit correspond each node, to know what burn is done when. The map is assuming optimal ,Hohmann transfers,. Other transfers are possible, like sub-optimum transfer that enlarge the transfer window or shorten the trip, for a greater dv expense. Gravitational slingshots are possible. ,Interplanetary Transport Network, exploit three body mechanics (a pain to simulate or predict, compared to patched conics) and Lagrange points to find extremely cheap, but often very long (time wise) paths. Hohmann’s transfers require instantaneous burns, which is a weak assumption for current powerful chemicals rockets, but do not hold using weak (but extremely mass efficient) ion thrusters, which needs to take a path that needs more DV. The map supposes all planets are on the same plane, which is false. Plane correction burns, which are generally shared between the initial transfer burn and mid-course, augment the cost of dv in a chaotic way, depending on the position of the planets during the transfer window relative to their ascending node. That is (partly) why Pluto does not appear on the chart : the trip cost vary so much that any value would not have been very relevant. The truth is, there is not much trade-off between payload and distance : each vehicle are designed for a payload and a dv budget, deviating to much in any direction often means that an other vehicle could fit better. I’d say that to be efficient, the payload mass has to be roughly in the same orders of magnitude of the last stage dry mass, and the delta-v will vary of roughly the engine exhaust velocity. All of that means that, the better the technology (engine exhaust velocity), the more flexible will become the crafts. Currently launch systems are mainly optimized for LEO+ : the flexibility allow for polar or retrograde orbits, but only the most powerful launchers could go up to GEO, but in practice, we design variants of generic launchers for such use. Once again, things might get better with technology and possibly mass use and production.
How much more energy would it take to send a rocket to the sun than to send one to Mars?
The answer to the amount of energy needed to send a probe to the Sun, as compared to Mars, depends on whether the Sun itself is or is not your actual destination. At the time of this answer, I’ve actually encountered this problem in the space simulator game, Kerbal Space Program. But let me use two real-world examples first. The ,Parker Solar Probe,, launched in August 2018, is a solar orbiter. It’s goal is to make many close orbits to the Sun to study its characteristics as closely as it can get without destroying itself. To help in all the examples, let’s imagine the Sun rests at the bottom center of a very wide, deep circular depression, like this: (Original work by AllenMcC. - This diagram was created with Mathematica, CC BY-SA 3.0, ,File:GravityPotential.jpg - Wikimedia Commons,) This is the ,gravity well, analogy. The pull of gravity is analogue to the energy needed for you to travel “up” and away from the Sun at the bottom of the well, to the top. Now imagine how other planets relate to it, as they have their own wells. Think of getting from Earth to Mars is like having a car with sufficient power and gas to travel “uphill” fast enough away from Earth so you can reach the “edge” of Mars’ gravity well. On getting closer to Mars, its gravity well will have more influence on your probe. This widely used drawing by Randall Munroe of XKCD pretty much nails the challenge. So while leaving Earth to get to Mars isn’t a trivial thing, it’s going to be easier than reaching the Sun. Remember that a rocket is just a vehicle. It’s not the same as the ,spacecraft,, which is its passenger, or ,payload,, to go somewhere. We’re not sending ,rockets ,anywhere. The rockets are sending spacecraft somewhere. Spacecraft often possess a little rocket energy of their own to move themselves once released, however. For either a Mars or solar probe, you need a rocket that can fly fast enough to spin around the exterior of the well…that is, achieve an ,orbit ,around Earth. You’re still trapped in Earth’s gravity, however. So the next phase is to use more energy to not only get uphill from Earth and to Mars—remembering that both Earth ,and the Sun, are trying to pull you back. That’s ,escape velocity. All of this energy is commonly expressed as ,delta-V,, or change in velocity. We’ll use kilometers per second for the measurements. Here’s the energy needed for an Earth-Mars trip, from Earth’s surface to an orbit of Mars, ,based on this handy delta-V map,. I’m not a mathematician or space scientist, so this stuff is going to be rough. Earth orbital delta-V: 9.4 km/s Escape velocity from Earth orbit to Mars transfer trajectory: 3.6 km/s Braking to enter Mars orbit: 2.11 km/s Total delta-V budget for a Mars orbiter to reach its destination: 15.11 km/s Now, if you don’t bother carrying much, or any additional fuel to Mars, you can use the planet’s thin atmospheric to make aerobraking passes in the upper atmosphere to slow down. Or, in the case of landers and rovers, ,you just drop right into the atmosphere,. You’ll save at least 2.11 km/s that way. Now let’s plot how much energy that the Parker Solar Probe needs. An important point is that PSP isn’t designed to slow down., It simply wants a course that will let it spin about the Sun without falling too close to it or into it. But the star’s extremely powerful gravity will cause it to fall ,very fast ,into its gravity well. Unlike most space probes to the outer planets, going to the inner worlds of Mercury and Venus takes you “downhill,” accelerated by the planet and the Sun. If you don’t adjust your trajectory right, you’ll fly past where you want to go. And today’s spacecraft really can’t carry a lot of energy. Unlike going to Mars, ,PSP has to try to decelerate a lot to reach where it wants to go. That’s why Venus is involved. The good news for PSP is that it can leverage gravity braking (or a ,reverse ,gravity assist,) around Venus, leveraging the planet’s gravity to slow down and adjust its course to reach where the scientists want the probe to be in solar orbit. PSP will make several encounters of Venus in the course of its mission to brake and adjust its course to get ever closer and closer to the Sun—about 3.8 to 4.2 million miles (Mercury orbits around ,36, million miles). My numbers are approximate because NASA took a direct-ascent path from Earth to Venus for the probe’s first flyby, skipping an orbit. The energy’s about the same, however. Earth orbital delta-V: 9.4 km/s Escape velocity from Earth to Venus encounter trajectory: 3.77 km/s Total approximate delta-V for PSP’s first Venus flyby: 13.17 km/s From here, PSP makes a series of orbits, accelerating faster and faster, making more Venus flybys over time. It’ll become the fastest human-created object by its closest approach: About 690,000 km/h (430,000 mph). It has maneuvering thrusters to make any course corrections to reach the flybys, but that’s not a lot of energy in them. So, as long as slowing down to reach a ,circular ,solar orbit isn’t your plan, Venus can help you get to an ,eccentric ,(wide and looping) solar orbit without a lot of power. But what if you’re going to Mercury? Now that takes a LOT more energy if you tried to build and fly a rocket and spacecraft that used nothing but its own energy to reach Mercury orbit. Earth orbital delta-V: 9.4 km/s Escape velocity from Earth to Mercury transfer trajectory: 3.49 km/s Braking into Mercury orbit: 9.59 Total approximate delta-V to put a Mercury probe into orbit: 22.48 km/s No real-world spacecraft can do a direct Mercury transfer. Instead, several reverse gravity assists of Earth, Venus and Mercury are used to slow down to reach a Mercury orbit. That’s what the ,BepiColombo, probe is doing. In Kerbal Space Program, I have a career mode mission contract to rescue a Kerbal stranded in close solar orbit. KSP’s solar system is comparable to Earth’s, but scaled down. Even so, you can see the challenge I have when you compare the orbital speed of the Mercury analogue, Moho, to the orbital speed of the vehicle I have to rendezvous. My rescue is moving almost twice as fast as the Mercury-like planet and about as close as PSP gets to the sun on a flyby. I should mention I need to bring along sufficient fuel (mass) to drag the Kerbal away from the sun and back home. The idea of trying to catch something moving as fast as PSP, gets is probably the hardest thing I’ll try to do in KSP—and that’s despite the fact that I can add far more energy on my rockets than the real world allows.
What makes SpaceX's Starship different and better than other rockets, is it faster, cheaper, or what? How will Starship change the way we travel in space and the way we explore space? When will Starship be commercialized?
I will try to be unbiased in this answer, but honestly I think SpaceX is setting itself up for short-term failure with Starship, so just a fair warning. Also, my TL;DR is at the end of the answer, so if you want to skip a LOT of information, feel free to. But if you have any comments to make, please read the whole thing through before you make them. I tried to make this answer as comprehensive as I absolutely could, so it resulted in an answer that was EXTREMELY long. The Starship System isn’t better than any other rocket current or past, nor is it the holy grail of rocketry. There, I said it. A comparison of the various past, present, and future rocket systems. SpaceX likes to brag that their reusability makes them better than any other rocket in the history of ever (especially SpaceX fanboys, sorry, not sorry). But the fact of the matter is that in order to become reusability, it requires a cost. The Falcon 9 is used as an example that it makes space travel cheaper. And while this might be true to some extent, especially when used in a rapid launch cadence, the truth is that in order to make it reusable, the Falcon 9 cannot haul as much stuff into orbit as a lot of other orbital class rockets simply due to needing to conserve fuel. It manages to counteract this a bit by just being much larger than most rockets for that weight class, but it still is a loss. A chart of all in-use and retired rockets that are in the Falcon 9’s lift capability. It took me two and a half hours to assemble this information, so please appreciate it lol. I tried to assemble a general conglomeration of rockets in that weight class. As you can see, the Falcon 9 is actually one of the least efficient rockets on this list, as evidenced by the specific impulse. Specific impulse is a measure of how efficiently a given reaction mass engine (i.e. an engine using propellant) creates thrust. The higher the number, the more efficiently it uses a given mass of propellant to produce thrust. This is why the rocket actually ends up with one of the largest by volume first stages of all these rockets, because it needs a LOT of fuel to achieve the weights it does, and yet still land again. Additionally, the Falcon 9 actually has two different landing forms, Return To Landing Site (RTLS) and Autonomous Spaceport Drone Ship (ASDS). The RTLS version requires a much larger loss in payload capacity, as the rocket has to not only make it beyond the Karman line, but also make it all the way back to the launch site. The more normal version that we see on the regular is the ASDS landing, where a ship out at sea is waiting to catch the rocket as it falls back to Earth, only controlled by its grid fin assembly. Falcon 9 RTLS flight profile. As shown, the first stage must fire its engines back to the landing site, which requires extra fuel. Falcon 9 ASDS flight profile, which only requires the booster to fire to land on the ship itself. To top all this off, as something to think about for the reader, the launch and landing both require vast amounts of infrastructure, especially the landing. Running the drone ships, keeping the pads in order, etc. all this requires money, time, and labor to get the rocket back to base to be reused. Hence, there are a lot of rising claims that SpaceX is actually underbidding its opponents to get as many launches as possible, as that is the only way that this sort of launch setup works long-term. In fact, we might already be seeing this. The last several months of Falcon 9 launches have been almost exclusively Starlink launches, which are funded by SpaceX itself. Hence, a lot of people are starting to suspect these launches aren’t as cheap as claimed. I am not saying I am an expert on any of this, but these are things to consider when thinking about Starship. Now onto Starship. I do not deny that it has some incredible engineering design and development under its fins. The rocket is designed to try and be as easily manufacturable as possible, using common materials and components that can be produced in a manufacturing environment on the regular. The engines on both the booster and the rocket are the same to avoid having to build two different engines. Basically, trying to use lean manufacturing methods on rocketry. The most recent prototype, SN15, after four full scale prototypes met their firey ends, actually managed to stick the landing profile that SpaceX has been trying to get for two years now. It flew up to 10 km, then belly flopped, and when it reached only a few hundred feet off the ground, fired its engines back up and landed upright. The philosophy behind this actually makes a bit of sense. It mimics the Space Shuttle in that it uses the increased surface area of the belly of the rocket to slow down its reentry speeds to about 100 mph, but then uses the Falcon 9 style of landing to reduce the need for a runway and wheels that the Shuttle did. However, the safety aspects of this are in serious doubt. NASA’s human certification rating usually requires at least two methods of landing in order for it to be certified. With Starship…that’s kind of impossible. By the time the system would realize a landing of this type wasn’t going to work, the rocket would be too low for parachutes. Its main engines are on the bottom, so those won’t help it. And trying to attach engines strong enough to lift this behemoth on its belly is essentially asking for more Raptors to be mounted to it…which kind of defeats the whole purpose of building it this way in the first place. Not to mention, the NASA certification process takes YEARS to finish. Mutliple launches, proof of solidarity, etc. there’s a LOT that goes into human certifying rockets. Hence why the US has only had about 10 total launch vehicles human certified as of today (only the Soyuz, Falcon 9, Atlas V and SpaceShip rockets are in use right now. The SLS will be certified following Artemis 1, Atlas V is certified but not flying humans until Boeing’s Starliner capsule is launched later this year, New Shepard is set to fly humans in the next year, and Starship is hunting for certification within a year for its Dear Moon mission). A diagram, in order, of all manned spacecraft ever made. While the Buran and Ares I never actually flew with humans, they both did pass the certification that would’ve allowed it to be used as such. The Buran failed due to the collapse of USSR, while the Ares I vehicle was originally intended to take astronauts to the ISS, but was replaced by Commercial Crew Program and, as a part of the Constellation Program, was shut down in favor of funding the massive SLS. Now, this is kind of where questions about the future of spaceflight will be decided. As of right now, no humans are legally allowed to fly on rockets that are not certified within their country of origin. However, all manned programs up till this point have been a government astronaut/cosmonaut/taikionaut/what have you. There have been private fliers to the ISS before, but they were on already proven launch vehicles. There has never been a non-government certified human flight vehicle that was actually available to commercial customers. So that begs the question, will people be allowed/want to fly on this spacecraft if NASA doesn’t certify it? NASA has traditionally shied away from propulsively landed vehicles, i.e. the propulsively landed Dragon space capsule. Not to say they have been outright against it, but the risks associated with such a system are far more likely to fail than if you use a parachute, which only has technically two moving parts, and can be directly computer controlled. CG animated landing of the propusively landed Dragon capsule. There is also the problem of the payload. The Starship is a two-stage-to-orbit vehicle. The Super Heavy booster will launch the Starship up to about the altitude that the Falcon 9 first stage does, then propel itself back to the surface for a soft landing (with its size, it will essentially have to go the route of RTLS, which will seriously degrade its performance). Starship itself will continue on until it reaches orbit. From here…it can’t do much of anything. This kind of flight profile will empty out its tanks to be able to haul the claimed 100,000 kg into Low Earth Orbit (LEO). Elon himself has stated this. Problem is, the large-scale, in-orbit refueling that Musk is banking on…doesn’t exist. It has never successfully been accomplished by ANYONE in the space industry, NASA, Russia, etc. because of the basic fact that fluids like to expand to fit their containers in a non-gravitational environment. The ISS and MIR space stations were refueled and resupplied by the Progress, ATV and Space Shuttle missions, but they can only do so through specific connection interfaces with the Russian side of the station, and only transfer about 200 or so gallons of propellant, along with some water and other various fluids that the people aboard it need to live. They don’t pump thousands of gallons of propellant between two large, but not space station sized, vehicles. Plus, the vessels sending the fuel to the station aren’t design to then land again, they simply burn up in the atmosphere (or in the Shuttle’s case, it would have extra tanks in the payload bay to refuel it). Meaning, they can fill up their propellant tanks with as much inert gas as they want to squeeze as much of the fuel out as possible. Starship won’t have that luxury, because as any engineer or rocket scientist will tell you, gas pockets in your rocket system are…unwise. Not an actual example of this happening, but there are instances in other rockets where this was the result. Final issue I see as an engineer in the whole concept of Starship, is the fact it is meant to go to Mars. That is a six month flight, and in those six months, based on readings from our unmanned probes on their way to the Red Planet, a human would receive as much as 60% of a human’s LIFETIME limit of radiation, if not more…on the ONE WAY TRIP. A graph of the estimated dosages of radiation from various sources. NOTE the scale on the side before you mention how close the bars of the graph are to one another. They grow by factors of 10 every time. So that 180 day transit will provide SEVERAL times as much radiation as the limit for workers on Earth are recommended to receive. Elon has claimed that it “isn’t that bad”, but when your spaceship is only protecting you from radiation via stainless steel…well, there are much more safe places I would rather be at that moment in time. So those are the moral and technical issues and concerns with Starship. Not to say they can’t be overcome, but they will be hefty hurdles to get over to make this vessel even able to carry humans, much less as much payload as they are claimed to be able to as far as places like Mars. The final hurdle, the one that I doubt the MOST of any of the claims, is the cost of launching one of these things. Elon has claimed and stated, and it has been repeated over and over and over, that the Starship will be able to launch for $1 million to $2 million a launch. This is not only a bald faced lie, but an impossiblity, because the claim is for if Elon can build 1000 of these things, fly them THREE TIMES A DAY, and do this across TEN YEARS. And the low end of that claim only covers the estimated $900,000 in fuel costs. If this was PRACTICAL, yeah, sure, you could make those numbers work out. But, as an engineer, I can definitely tell you that it is NOT. The absolute RECORD for the turnover for a rocket is 27 days, held by a Falcon 9 Full Thrust (Block 5) booster. If a MONTH is the record…on a rocket that is FAR simpler than the Starship…how the HELL are you going to achieve three flights of a rocket…IN ONE DAY? Times a literal THOUSAND? The $2 million claim is if you can keep up those 1000 rockets, ALL of them flying 3 times a day, and pay off all the infrastructure that these things require over ten years. You see how impractical this would be? From just a common sense perspective? Not only would you need to ignore all upkeep costs on a daily basis, i.e. repairing the launch pad, transporting all these behemoths to and from the stacking and refueling bays, all the labor involved in what would almost out of necesscity be a 24/7 flight schedule, but you would have to ignore the fact that one day, almost guaranteed one of those ships will fail. How quickly can you clear away the debris? Will the other flights in orbit be stuck there until an investigation is completed? What will happen if there is something major wrong with these vessels, and some of those in orbit already have people aboard them? Only another Starship could come to get them, because there is no other rocket in any country that is aiming to get 100 people at the same time into orbit. Not to mention, as far as I have heard, there is no transfer between two docked Starship vessels…so how will untrained humans be able to conduct an EVA? That is a process that takes astronauts YEARS to perfect, and they have mobility attachments to their suits that allow them to have RCS thrusters on themselves to manuever. This isn’t KSP unfortunately. RCS packs in real life are almost as big, and are as heavy, as the person wearing them. This all adds up to very quickly disproving Elon’s claims. Even the Falcon 9, a simpler, smaller, basic, unmanned satellite launcher takes a month to turn around. A manned vessel should take longer than that, especially one as big and complex as Starship. Now, none of this is to say that the costs won’t go down over time. But multi-hundred millions is where I would estimate these launches would go, as the infrastructure has to be supported, repairs must be made, labor must be paid, and the investment costs of the rocket itself add up to almost what the SLS has accumulated over its longer timeframe. A timeline of SLS costs, which over nearly a decade add up to $17 billion. A decent lump of cash. Starship on the other hand, has already been estimated by Elon at about $5 billion dollars…over only four years. That is almost the same yearly cost of SLS. And those costs keep going up. A few months before that one^, Musk claimed that the developmental costs would only be $3 billion. I normally don’t like using the same source twice, but there isn’t much out there on development costs for Starship, unless you are one of the investors. Not to mention, NONE of these numbers has included Musk himself stating that “the Falcon 9 costs about $54 million to produce, so Starship will be about four times that.” That’s over $200 million per rocket. Not close to the current claims of SLS being about $1.2 billion per launch, but funny enough, no one assumes it will launch 10 million times over 10 years (LITERALLY). Because it is an absurdity. If the SLS could pick up its cadence, over time it could easily drop itself to an easy $500 million per launch as the developmental payoffs happened. Maybe not Starship’s claims, but keep in mind, the SLS can launch its Orion capsule in its first iteration all the way to the Moon in ONE launch. And it will achieve between 90 and 100 tons to LEO, and about 28 tons of that to the Moon, in that first version. With the upgraded versions being able to haul over 130 tons to LEO and nearly 50 tons to the Moon with one launch. Starship will need at least two, if not more, launches to get 100 tons to the Moon as Elon claims. And if we follow that logic, even assuming they only build two rockets and just fly one of them multiple times to refuel, you are looking at over $400 million in building and refueling costs alone. That isn’t including all the developmental costs and infrastructure charges that no one wants to do the math on like they have SLS. But, that 100 ton payload, assuming it can (which it certainly seems like it could), would be equivalent to two SLS launchs to the Moon in weight. So something to take into consideration. For comparison to these rockets, the Apollo Program’s Saturn V launched just a bit over 125 tons to LEO and a little over 40 tons to TLI (Trans-Lunar Injection). It also is still the only rocket to carry humans beyond LEO, which means it is the King of the Mountain until such time as some other rocket system beats it. Which in all honesty, is going to probably come down to the SLS vs. Starship. There’s very few other vehicles in development that even approach the planned capabilities of these two behemoths, and the ones that are, don’t plan to launch till the late 2020s or early 2030s. So, I apologize for how long this was, but I wanted to get a lot of stuff out there that I have talked over about with a bunch of friends of mine who work at varying space groups, including NASA, Boeing, Lockheed, SpaceX, and Blue Origin. TL;DR,, Starship is considered “unique” because it aims to be the first commercially built and launched rocket that will be classified as “super-heavy” with a human rating (Falcon Heavy could’ve been the first, but without human certification only achieves the super-heavy profile). Additionally, it aims to be reusable, be refueled in orbit, be ridonculously cheap, and be an engineering marvel on its own. In one respect, it did achieve the engineering marvel already. Just its Raptor engine is proof of that, being the first full flow staged combustion cycle engine ever flown, as well as having the highest chamber pressure of any rocket engine in history. And its landing is even more impressive because, personally, I didn’t think they could do it. SN10’s MOSTLY successful landing. It blew up on the pad 15 minutes after this landing due to it shattering its own tanks with that little bounce you see as it touches down. So, it has already done extraordinarily well. It aims to be reusable, a factor that has yet to be proved, and we will have to wait until they start commencing orbital tests to see that. The first one is supposed to take place either late this year or early next year, and will see the rocket launch from Boca Chica, have the Starship released from Super Heavy above the Karman line, have the booster come back and fake land in the ocean off the coast of Boca Chica, and have Starship reenter the atmosphere before making orbit over Austrialia, with the aim to soft land off the coast of Hawaii. So we won’t see it reused, but we CAN see if their landing maneuver is actually feasible if they are trying to come back from space. The in-orbit refueling isn’t something that is IMPOSSIBLE, just difficult with current technology. It will probably be achieved in the near future, heck, NASA is funding part of SpaceX’s research into it because it would be handy to learn for themselves for future plans for space stations and refueling depots. In terms of cost, based on what I see, both in terms of just general common sense over manufacturing, as well as SpaceX’s current system, $1 million to $2 million is just absurd, no matter what we say. Elon’s goal adds up to putting enough payload into orbit over 10 years to be equivalent to the Great Wall of China, two times over. Something that doesn’t even really make a lot of sense in the grand scheme of rocketry, considering that’s more weight than what’s been put into orbit since we first reached space in the 1960s, over 60 years ago. As well as the fact that in order to achieve that many flights, FUEL ALONE will cost nearly 10 TRILLION DOLLARS. Seriously. 1000 flights a year, times 10 years, equals about 10,000 flights per Starship, assuming absolutely NOTHING goes wrong (which it ALWAYS does, at the most inconvenient times), and there are 1000 Starships. If we assume $900,000 a flight just for fuel like Elon has said, that is $9,000,000,000,000. That’s nearly a THIRD of the entire US debt at this moment in time. So the monetary values that are claimed don’t make any viable sense for Starship to actually be flying at $1 million a pop. And don’t take any infrastructure, labor, or developmental costs into consideration. So this value just reeks of absurdity to me, and don’t make any sense to actually be used as commonly as they are for a reason why Starship is the holy grail of rocketry and all other rockets should be discontinued. So yeah, in my honest opinion as an engineer, Starship isn’t actually as great as it is claimed, and while it has some amazing pieces of technology, will never achieve the actual floor level costs it claims it will. It might be able to achieve everything else on its list, but that is the part that makes me doubt, and the safety of the thing coming from orbit will always be a concern for me. And, if you’ve made it this far, please don’t take my criticisms as a “IT WILL NEVER FLY OR SUCCEED” sort of thing. I’ve been impressed by what SpaceX has done thus far, but ,I believe that they are not the end-all, be-all of rockets for the future, simply the next stepping stone. Anyways, I’m off to plan my trip to watch Artemis 1 take off either late this year or early next year! Cheers!
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