IncongruousGoat

There's been some talk recently in the SpaceX thread about ULA's SMART reuse plan. Part of this plan involves using an inflatable heatshield to protect the (now-separated) first stage engines on re-entry, due to the high velocity at MECO. This led me to wonder... what's the current state of inflatable, deployable heatshield technology? It would require some highly flexible material that ablates slowly enough that you only need shielding that's as thick as canvas. A heatsink design seems out of the question - heatshield mass just doesn't seem like it'd be high enough to support that, at least not using any real material. I can't think of any material that would fit the bill. On the other hand, I am not a materials scientist. So, what research and testing has been done on this tech, and how mature, reliable, and cost-effective is it?

Also, the cost of that high-tech inflatable heat shield of theirs... Anyone in here know of a suitably durable and flexible material to use for something like that? It looks like they're planning to completely chuck it after every flight, which can't be cheap. Honestly, I'm starting to think that the main motivation behind SMART reuse is to avoid bottlenecks on engine production, considering the turtle's snail's pace Blue Origin moves at.

Acceptable by what metric? I mean, if you were trying to place the satellite in any old orbit, then you succeeded. The orbit wasn't planar, though, which might be a failure depending on what the satellite was intended for. If you were asking about the launch vehicle and profile, then there are all kinds of things you could improve. First off, your ascent profile was way, way off. Flying straight up and then turning sharply over when you reach space is probably the least efficient possible way to get to orbit. What you should do instead is fly what's called a gravity turn. This is where you gradually turn over during the launch, starting the turn at 100 m/s or so, and slowly leaning over during the rest of the launch, so that you reach horizontal just as you're reaching the highest point in your trajectory. This way, you minimize losses due to fighting gravity. There are plenty of resources on the forum on how to do one of these; I've only given a cursory explanation. The vehicle design also left room for improvement. First off, the Swivel is a terrible upper stage engine. It weighs too much. Its nominal use case is as what's called a sustainer - which is a long-burning central engine that's augmented early in flight by boosters of some sort. For your use case, the Terrier would have been a better choice. Second, the Kickbacks were not a good choice for booster. They're too large and powerful for the core stage you had. See how you shot off the pad? Your thrust-to-weight ratio must have been close to 2, when it really should have been nearer to 1.3 or 1.4. You lost a fair amount of delta-V to fighting the atmosphere. Third, you didn't give yourself any good sources of control authority with either your boosters or your first liquid stage - neither the Kickbacks nor the Reliant you used had any control authority. Either pick engines that do gimbal, add vernier thrusters (Twitch engines work decently well) for attitude control, or add some control surfaces. Fourth, your second liquid stage was nearly as big as your first liquid stage. Typically, you want the second stage to be substantially smaller than the first stage - at most half as large, and nominally somewhere around a quarter as large.

No, it won't. Remember how I said that the strength of the force of gravity depends on how close the two objects in question are? Well, what this means is that there exists a speed that, if you throw your ball at that speed, it won't fall back down. This is because it's moving fast enough that it's never slowed down any faster than the rate at which gravity is getting weaker as it moves away from the Earth. This is called escape velocity, and on Earth it's 11,186 m/s, which is 40,270 km/h or 25,020 mph. From some of the stuff you've said, it sounds like what you're doing is heading straight up until you reach escape velocity. It's easy to see why this might be confusing - reaching escape velocity will result in you not coming back down, since you end up in an orbit of the Sun. However, it's not really a productive way of getting to the Mun. Well, there's always MechJeb... But I tend to discourage its use in new players, since it can be used to avoid having to learn orbital mechanics, which in my opinion defeats the point of playing KSP in the first place.

All right. You've said that you don't really understand what an orbit is, so I suppose I should try to explain what an orbit is from first principles. I'll try to lay off the math as much as possible. Just as a disclaimer, I'm ignoring the atmosphere for much of of this explanation. The presence of air makes things needlessly complicated. First off, gravity. All things with mass pull at each other, with the pull getting stronger as the objects get closer. For most of the stuff you interact with on a day-to-day basis, this force is so weak as to be completely insignificant, but when you deal with objects as big as planets, moons, and stars, the force of gravity starts to matter. Something important to note is that when a very large object pulls on a very small object, the small object is going to speed up towards the large object at the same rate, regardless of how much mass the small object has, specifically. So, for example, a 10-pound bowling ball will fall at the same rate as a 15-pound bowling ball. If you're standing on Earth and you throw a ball straight up into the air, gravity will pull it back down. If you throw the ball at an angle, its trajectory (the path it follows as it moves) will form an arch shape (a parabola) - which means the ball flies along a curve. Now, this is the really important bit: the Earth is round. Gravity doesn't pull you down towards the ground, it pulls you in towards the center of the Earth. This means that, if you take your ball and throw it really, really hard, it'll fly so far that the direction gravity is pulling it will change as it travels. This is because the ball is moving with respect to the center of the Earth, so from the perspective of the ball the center of the Earth (and the source of all that gravity) is changing position. If you throw the ball in just the right direction, at just the right height, and at just the right speed, the rate at which gravity pulls it down will match the rate at which the center of the Earth changes position from the perspective of the ball. The ball will then be stuck, "falling" in a circle around the Earth. This is called an orbit. If you were to throw the ball at a slightly slower speed, gravity would pull it down faster than it could move around the Earth, and the ball would fall back down. If you, on the other hand, threw the ball a little harder, it would travel away from the Earth for a while, slowing down as it moves further away, and eventually falling back down and speeding up to the height and speed that you originally threw it at. The path of the ball now forms an oval (an ellipse). The highest point your ball reaches on this oval is typically called the apoapsis, and the lowest point is called the periapsis. There are other terms that describe this oval, but for your purposes those are the two you'll want to know. You're probably wondering, what do rockets have to do with this? Well, just trying to throw a ball (or a spacecraft, or a car, or whatever) isn't entirely practical. The speed you'd have to get to in order to orbit the Earth at 200 km up, for example, is approximately 7,790 m/s, which is 28044 km/h or 17425 mph. Way faster than you could throw, or even a bullet from a high-powered rifle. Plus, you'd need to have a starting point that's 200 km up. The highest point on Earth is Mount Everest, which is 8.8 km up. Not nearly high enough. This is where the rocket comes in. A rocket is just a means of getting your ball up to the correct height and correct speed, which it typically does by flying a curved path known as a gravity turn. This path heads straight up at the beginning, then slowly curves over to one side to build up the speed needed to get into an orbit. We have to use rockets because they're the only sorts of things that have enough thrust to take off from Earth and that work in space. Aircraft, for example, rely on the presence of the atmosphere, and so aren't useful sending things to orbit. The numbers are different for KSP (the game's solar system is built to 1/10th the scale of ours), but the concepts and physics are the same. If you have any questions, feel free to ask. I will do my best to answer.

If the weather is good, spend the day outside. Find a nice bench in a park and read a book, or just go for a long walk. It'll be your last chance to do that guilt-free for a while.

Well, for more realism I recommend going up to 6.4x scale, although it might put a bit of a crimp in your interplanetary colonization plans given how much harder it'll make everything. 3.2x might be a bit better. Just don't stick with the default scale; it makes everything way too easy. Oh, and Persistent Rotation. You'd be surprised how much of a difference it can make. For parts, I'd recommend SSTU. Lots of good engines and spacecraft, especially for the early work of colonization while you're still in chemical engine territory.

Well, I've been playing a lot of Realism Overhaul lately, so I need a ~3 second hold-down on all my launches to give my engines time to spool up. In stock, though, I start the engines and release the clamps in the same stage. The thought of wasting fuel on an unnecessary hold-down pains my inner efficiency-obsessed nut.

@jinnantonix Congratulations on completing the challenge! I liked the cage-style mothership especially (I've always been partial to that kind of design). You have been added to the Hall of Fame; feel free to pick up the badge at your leisure.

So... it's a space truck stop. Wow. Remind me to not underestimate the Teamsters again - their influence is clearly farther-reaching than anyone suspected.

Two words: gravity losses. When you fly straight up, you're always burning against the force of gravity, which means a good part of the force generated by your engine gets cancelled out by gravity. Think of it like trying to swim upstream in a fast-moving river - you're going to have to exert a lot of force just to not get swept downstream. When you're flying to orbit, however, gravity losses are far less significant, since you spend most of your time burning perpendicular or near-perpendicular to the force of gravity. The end result of this is that, even though it seems like you need a lot more delta-V to fly to orbit and then raise your apoapsis, it ends up effectively cheaper due to all the gravity losses you avoid in the process. The difference is exacerbated, of course, by KSP's toy solar system, since it's really easy to get into orbit in the first place. But that's a discussion for another time.

I'd say the vision is secure as well. From what I've seen of various interviews with Shotwell, she's an even bigger dreamer than Musk when it comes to that. Plus, I think most of the engineers working there also buy in to the vision, considering the hours they're working to make it happen.

43: A towel, to go with the copy of The Hitchiker's Guide to the Galaxy 44: A slide rule, in case of calculator failure

I have 10,000 snowflakes. So... I guess I can make a snowball? Hooray?

A picture from Death Valley in winter? All right, here's a picture from the Adirondack Mountains in summer. Specifically, from the summit of Gothics, taken yesterday.

Some more pictures from the Adirondack Mountains of upstate NY, this time from the trail up and the summit of Gothics:

The first is never going to happen. Phones just do not have the processing power required to run KSP, and there really isn't a way to get around that. The small profile restricts what's possible with the device, due to limits on the size of a transistor and because of cooling (or lack thereof). Also, a typical phone touchscreen doesn't have enough room to fit enough buttons to permit the playing of KSP. It's easier to list the keys on a standard QWERTY keyboard that KSP doesn't use than it is to list the ones it does. The second suffers from many of the same problems, considering the complexity of the editor controls (and there really is complexity in there), as well as the amount of KSP that you'd have to port, and difficulties getting files to and from the phone. Oh, and the craft designer would be worthless for modded installs, as well as career and science mode, and you'd have problems dealing with Making History. I can't think of a workable mechanism for pointing the designer at a KSP install on some remote machine, which makes it a bit difficult to use. Oh, and the demand among the playerbase just isn't high enough to make an enormous project like this one worth it to the devs. The number of people who've said "Oh, I wish I could play KSP, but I only own a phone" is not very high.

You know what this thread doesn't have enough of? Folk rock.

Well, if you've only been at it a week, how do you know you hate it? What language(s) have you been trying to learn, and what resources have you been trying to use to teach yourself? You could easily have picked a badly or confusingly designed language, or simply been using a bad resource for learning, without realizing it. There is something else to this general problem, though - to design your own programming language, you're going to have to teach yourself a good amount of theory of computing, in order to not design a language that is either impossible to parse or insufficiently expressive to do what you want to do. And if you think learning a programming language is boring, just wait till you get to finite state automata, context-free grammars, and Turing completeness. Writing your own programming language could easily become at least a master's thesis if you make it interesting enough.

Ohhh boy... Compiled or interpreted language? Both are going to require a tokenizer and a parser, but the semantics are typically different. From what you've said it sounds like you're writing some kind of interpreter, since you're talking about scanning directories (which wouldn't make much sense for a compiled language). If you are in fact trying to make something useful for aerospace, I recommend you re-think this choice. Interpreted languages are typically far slower than compiled languages, which isn't good for the kinds of high-performance computing needed by aerospace. Additionally, you've already gone and assumed that you're going to be running on some system that has a directory tree. This isn't guaranteed - plenty of microcontrollers don't (and can't) run an operating system in the first place. Even if you're running on something with a directory tree, though, you'll have to deal with cross-platform compatibility. You say your language is based around "operations". What, exactly, do you mean by this? Because depending on how you define these operations, you could easily end up with a language that isn't Turing-complete - i.e. a language that is essentially useless for computation due to its limitations (this is a generalization, but for our purposes is close enough). It sounds to me like what you're shooting for is some sort of grammar for defining the operation of a finite state machine, which wouldn't be Turing-complete.

Nope. The current record for turnaround is 12 days, 4 hours, done at LC-39A between BulgariaSat-1 and Intelsat 35e.

Sourcing could be diversified, but SpaceX would never agree to it. Their whole shtick is extreme vertical integration, because it drives costs down. Sourcing large components of the BFS from all over the country would do exactly the opposite. Remember, SpaceX aren't trying to just go to Mars, they're trying to make going to Mars a financial possibility for as many people as possible. They're not going to take any step that would lead to increased manufacturing costs on the BFR without improving the vehicle itself, regardless of what short-term funding they could get for doing so.

Because NASA is beholden to Congress for its money, and Congress for the most part only cares about keeping the pork barrel train running. Working with SpaceX on a heavy-lift vehicle doesn't qualify as keeping the pork barrel train running. I mean, SpaceX only has major facilities in 4 states! How is the noble state of Arkansas supposed to profit from this endeavor, I ask you?

This is the booster that launched Bangabandhu-1, right? For some reason I can't find any concrete mention of which booster this is anywhere. EDIT: Live stream confirms, this is the booster that was used on Bangabandhu-1

I will call an animal "he" (or she, or other) if and when said animal asks me to do so, and not a minute before. Until then, what I call the animal is my choice and my choice alone. Not like the animal cares, or could ever know what it would mean to care about something like this. I respect intelligence, not the ability to flail about. So sue me.