wumpus

From what I've heard, successful abort simulations were the exception, and plenty of abort scenarios had zero successes in the simulator. Soyuz had two atmospheric* faults requiring aborts, and two successful recovery of cosmonauts. Aborts that don't rely on using nearly the entire spacecraft to return to Earth appear superior (which might be an issue for Starship). * IRC the first was needed before launch (and was an issue getting the signal from ground control to the spacecraft to abort), but that was still "in atmosphere" and "needed an abort before the rocket exploded".

"Tranquility Base" beat them both.

I'm pretty sure most of that was customer driven (government customers like to pile on requirements at the last minute. Contractors rarely want last minute changes). That said, if KSP is any indication, long sideways coasting is ideal for reducing velocity and making such landings easier.

~1km/s is roughly mach 3, which by my ancient rule of thumb implies that you could reduce the mass of the rocket in half. This gives you a similar problem to the Stratolauncher, where there is no feasible means to scale up your rocket to respond to what payloads need to be launched. On the other hand, that type of velocity through the atmosphere might be ideal for a ramjet/scramjet first stage to get another 1km/s or so and lop another 50% (75% total) off the rocket. Don't forget that Falcon 9 second stage is nearly all fuel, while the first stage requires 10 times as much thrust, and I'd expect that it would also be more hydrogen-friendly (and only need one type of fuel).

The Isp of a photon rocket is already infinite. Photons have momentum, but zero rest mass and thus divide by zero in the rocket equation. On the other hand, photon rockets have a miserable energy efficiency, so aren't used at all.

If you simply wait until the function returns a value, it makes little sense to delegate the work (you might as well have the original processor do the work). The whole issue comes up when the initial processor keeps going and the other processor completes the work at some unpredictable time, often causing unforeseen difficulties. I suspect that my wall of text will only make sense once you look into the various options of running on more than one CPU, especially with python. If you plan on multiple CPUs on a rocket, you might want to go with a raspberry pi or similar (multiple cores, each capable of running python).

Reading through the datasheet to integrate a I2C accelerometer can be interesting and may require you to understand low-level programming. I spent far too long finding out that you needed to send two bytes in "multi-byte mode" instead of sending them one at a time to a similar accelerometer. Hopefully you can dig up Python libraries/drivers that would work. You never know exactly when the communication will happen, and if you are sharing memory it has a nasty habit of overwriting half your buffer with different data than the other half (Python only guarentees that each *byte* is correct in such situations. A 32 bit value can have the most significant bytes from one value and the least significant bytes from another. If you can structure the overall system in such a way that all communications can be stuck in a queue (google "producer consumer multiprogramming"), nearly all the pain disappears (but it may be slightly worse than one monolithic program, or not depending on the complexity of each unit. By "stuck in a queue", I mean a single packet (probably a class or something, maybe just a variable) sent to a single point. That point might be used by more than one process/CPU, but it isn't all that critical *when* it grabs it. Once this second process is done it will look for a new packet to process. The system should be able to tolerate more than one item backed up in the queue, especially if you are sticking to an interpreted language like python. If you can manage to build your system this way, the difference can easily be between "you will never get the bugs out after months of debugging" to "your system is using all the cores/threads in your CPU in less than an hour". And yes, both situations are from personal experience (although the "in one hour" situation was particularly friendly to parallelism, but it was also my first chance to program a system with multiple CPUs). And to a certain extant, this is the only real way to use more than one core on a computer in python as the "multiprocessing" module doesn't share memory ("threading" shares memory, but python has a GIL that prevents more than one core/thread operating at once).

Superheavy is a misnomer, unless you include the mass of the orbiter itself. I'd only rate it heavy, considering that Saturn V already existed. I wouldn't be so sure about seeing "something like it again". There seems to be a strong desire among NASA and space committee Congressmen to see things like "spaceplanes" and "SSTO" without understanding that the present infrastructure simply isn't capable of efficiently building such things. So expect to see things like Dream Chaser well funded, regardless of how much it costs to boost those wings into orbit. I still maintain that it was exquisitely successful in managing Congress to fund it for 135 missions. Good luck getting that kind of funding again. Let's hear it for the sunk cost fallacy!

Note that my equations are a tad ... optimistic. A better assumption would be to convert the entire energy to gamma rays, and then compute the momentum they contain. Of course, the reason I mention gamma rays is from electron/positron annihilation while antiprotons (and anti-neutrons) would provide most of the energy. But the point is that you need very, very little antimatter to get off a planet. Just don't ask how much it costs to make even that amount of antimatter using 21st century methods.

They might fish the second stage out of the Pacific, but there's no way that the second stage is returning to Vandenburg. I don't think it was a Falcon Heavy either, which would make it easy to make that mistake with the two "return to launch site" boosters.

Once it hits antimatter it isn't [molten] iron anymore. It is pure energy. And that plume will have many of the nasty effects of neutron bomb radiation flying around so you don't even notice the trickle of unburnt iron. Antimatter is something that exists and researchers have managed to store. Anti-gravity is pure fantasy, although for all I know we might manage anti-gravity before finding a means to mass produce antimatter. But I'd still recommend leaving the anti-gravity off, and simply using the anti-matter drives to leave each planet (it should barely take any antimatter). If you want an even less exotic fuel (although it might seriously date your science - it could be quickly proven impossible/wrong): try metallic hydrogen https://www.youtube.com/watch?v=nMfPNUZzG_Q

This is two questions: 1. What effects would a device to neutralize gravity's pull have? The amount of fuel required to launch/land/move between planets approaches zero. Simply burn enough fuel to reach a speed that will get you there in a reasonable time, then burn the same amount of fuel to stop. Note that according to general relativity, the internal effects on a spaceship due to acceleration is identical to gravity: your gravity neutralizer should remove all acceleration issues from your craft (possibly also providing a steady 1g for the crew), so you can accelerate as fast as the engines can without squishing your crew. 2. How much power does antimatter have? Good question. The energy levels are extremely straightforward: E=(2)mc2 tells you how much energy you can get out of the antimatter (the 2 is because regular matter is "free", and we only care about the antimatter). v=mv2/2, so a 100% antimatter engine would net a velocity of 2*sqrt(mantimatterc2/mtotal_rocket_mass). Switch to relativistic equations (not much harder) if you notice your spacecraft is going more than 10% of the speed of light. Don't expect 100% conversion, and a better method would be figure out how the Orion worked (it was designed to efficiently use the momentum generated by atomic explosions, should be similar to your antimatter), and work out the math from there. Also liquid hydrogen is a terrible material to use for reaction mass: it is one of the least dense things in the universe and has to be kept terribly cold to avoid being even less dense. Water, CO2, air (N2), argon, iron, regolith would all make better forms of mass to through at the antimatter (you might care to have something that can work with a "fuel injector" of some sort, just don't be too picky about it. The means of constraining the antimatter will be really weird and high-tech, so melting and squirting molten iron would be a no brainer compared to injecting antimatter.

How does the saying go? Horseshoes, hand grenades, and nuclear weapons? Sputnik certainly showed that the R7 could be maintained within a few degrees of target all the way around the world (this might not hit Washington DC, but the place might as well be surrounded by "consolation targets"). The real problem was that aside from recon, there was no particular reason to send up a spaceplane. And only the spaceplane was likely reusable, so the costs would be vastly higher than using an ICBM or a capsule. A spaceplane is like a flying car: it is trying to cover two worlds that aren't similar enough for one design to cover both. The Air Force certainly wanted a spaceplane. They had plans for a spaceplane. But the laws of physics, mainly the rocket equation (and thermodynamics for the X-15 (not that the X-20 wouldn't have reentry issues)) made it next to impossible to build an effective spaceplane. Once Sputnik and Yuri Gurgarin made it clear that the US needed to get in space *now*, this impossible dream needed to be sidelined (but kept popping up in Shuttle and Dream Chaser). It is almost like a faction in NASA/USAF have this steampunk-like fantasy, only instead of Victorian-era they want the sci-fi of the 1950s (with spaceplanes, not Elon Musk's tail-lander 1950's throwback). It doesn't matter how badly this fits the situation, they just demand that style. Edit: there also seems to be a faction demanding SSTO. How you can make funding decisions at NASA without understanding the rocket equation I'm not sure (except after hearing second hand how such things are handled, I'm no longer surprised), but far too many things get budgets for this stupid fantasy.

Looks like the X-20 uses a similar strategy as the Shuttle in returning from orbit. I wonder if they would have had similar (or worse) issues with tile replacement on the X-20. A point of view that insisted that the glory of the air force officer corps trumped such unimportant issues such as mass when going into orbit for example... Van Braun showed that missiles were an effective (if overexpensive means for delivery of conventional ordinance. Although sending bombers straight into the RAF to attack London instead of attacking the RAF directly was probably even worse) means of delivering bombs. It just didn't get Air Force pilots those required combat missions to advance. Recon made a lot more sense for manned missions: the means to return film from space might have impressed Rube Goldberg (at least until electronic cameras and storage caught up). Doesn't look like they would have any advantages of looking through less atmosphere. Combat: see bombing run, and even less reason to drag around all of that non-weapon mass. The X-20 program simply was a preview of the Shuttle issues, where the "spaceplanes are cool" vision won over boring issues of mass. Seeing how it was started in 1957 (when Sputnik launched) it was hard to believe it managed to continue through 1961 (Shepard's suborbital launch) and 1962 (John Glenn's orbital flight), although it is possible that it was hard to kill space programs during the spacerace. Oddly enough, the Saturn 1 had lifted off in 1961, paving the way to lift such heavy contraptions and might have saved the thing. But it must have been disheartening watching the string of failures to respond to Sputnik all the while knowing you had to build a far more massive booster to heave this heavy load into orbit. For those interested in the Dyno-Soar: it is Amy Teitel's favorite spacecraft and a number of videos should be on "Vintage Space": https://www.youtube.com/channel/UCw95T_TgbGHhTml4xZ9yIqg

As much as I love the idea, two huge issues almost certainly killed it. 1. Do you really think it is easier to provide 7000m/s to an X-15 than 9400m/s to a Mercury capsule? They aren't light, and don't really have the delta-v (only 2400m/s) you'd expect from an upper stage. 2. Re-entry heat. A X-15 goes to heroic efforts to survive the heat from extreme speed, but it isn't designed for 9000m/s. All returning spacecraft that I'm aware of keep the compressed heat away from the spacecraft to minimize heat. A X-15 simply attempts to survive the heat, which is unlikely to work at de-orbiting speeds (it technically did re-enter from space). It is also low-drag, so it will have to survive those temperatures for much longer and will certainly vaporize.

I doubt they got far enough to worry about such things. I'm also continually amazed at how early some tech appears: there was a team seriously trying to put the first man in space with ramjets as a significant source of delta-v! If you don't know what "isn't possible" with your infrastructure, there's often no reason not to try it. Pretty much every "fancy" tech in cars (except maybe some stuff that absolutely requires computers) was available in the 1920s. Mass producing long-lasting parts would often take till late in the 20th to early 21st tech.

Gemini: Elon is waxing and Shotwell is waning. You need to reach out and touch someone* (preferably via outrageous tweet). * this was an old ad slogan in the 1970s-80s by AT&T to sell more long distance calls.

That sounds better. I've been going by some old article (probably popular mechanics or similar level) that presumably thought the stuff was classified and came up with that claim of price. I wonder if it was true in the 1950s, when Scotland was likely broke and JP7 was new? That still seems low for such a specialty item, and don't forget the factor of 10 markup when selling to the government* (that isn't all profit: all the paperwork and regulations involved can eat up the markup and then some), but a lot closer than my "fine scotch" claim. * I think my number comes from selling floppy drives to the government (if not, a similar device where I was more than familiar with wholesale and retail prices). The price included a ton of support and replacement provisions, along with fully custom mounting/enclosures (the *real* enclosures were often milled out of solid aluminum and cost far more than any electronics inside) and the government buyers didn't blink at the cost.

You mean the M-21? Scurries off to read article... er, no. But still killed by the disasters encountered by the M-21. My understanding from general back of the envelope math is that launching a rocket at mach 3 should reduce the amount of fuel needed in the rocket by about half (doesn't take into account that the first stage can approach vacuum efficiency throughout its flight). On the other hand, there is the issue of supplying enough JP7 fuel (said to cost as much as fine scotch, and burn almost entirely running on afterburner) to get the AP-12 (nee SR-71) to both mach 3 and 20,000m. Same issue that the stratolaunch has: it almost always makes more sense to stretch the first stage fuel tank out rather than use an air launch. Of course with the stratolaunch, it *might* make more sense now that the plane is built and paid for, but it still has to compete with simple SRBs ringing the first stage (if thrust is limited from the extra fuel).

Back in the 1990s I was running some equipment through tests before it could be put on board (military) submarines. One of the tests involved susceptibility to magnetic fields: the device in question was placed inside a 2m circle of highly wrapped wire (enough to drop 150VDC without too much of a short circuit). When they ran the test, the wrapped wire instantly aligned itself with the Earth's magnetic field, but my device kept on chugging. The device was primarily a video display, and fortunately used the "fancy new [for the time]" LCD displays. I knew when I saw that test I couldn't have passed with a CRT (without a lot more work and a ton of research).

Nobody has mentioned loading times? I've heard of some horror stories on the "how many mods do you have and how long does it take KSP to load?". I have a bunch of mods included, but I think most of them break compatibility and aren't loaded (I think the "real astronaut/cosmonaut voices" mod is in there, but doesn't make any sound). KER is the only one that I can't live without (I suppose I could figure out how to use the stock readouts, but I'm used to using KER while building/flying rockets).

Long, long ago I visited Patuxent Naval Air Station (a place where the US Navy tests aircraft, vaguely near Washington DC and Wallops Island) and was told that one of the ways pilots could wash out of the test program was "no apparent fear of death". I suspect these pilots have the badS flag set.

SSTO implies a tech level so much higher than ours it isn't clear exactly what you are optimizing. Does aero matter? Then you want a classic tall, thin cylinder ("rocket shaped"). If construction materials matter, then a fat cylinder. If ease of construction matters, then a large cube. Also note a large, fat, cylinder might be ideal for keeping a reasonable g-force by spinning. If you assume that future tech will be built around 21st century ideas, then a fat cylinder is a good bet. In reality, expect spaceship designers to care more about "cool" and "tradition" than coming up with a design from a clean sheet of paper for every planetary surface they land on. Once a design solidifies into one traditional form, it is hard to convince people to accept another form. PS: I'm not sure what Isp you need to make SSTO happen, but expect it to be more than 500s and closer to 1000s. You can't realistically upgrade the shuttle (or add aerospikes) and make SSTO happen on Earth (without a tiny payload that could be easily comfortably sized had you used TSTO).

I'd suspect at least some initial training in Java. I can't imagine why anyone would build a class to call something built into the language. Unfortunately, this looks like something that will lead you to threaded code way too soon. Of course, so will doing real time rocket control.

Sounds like it is due to mechjeb putting everything at exactly equatorial inclination and a 100,000m orbit. Sooner or later you will hit something in that tight ring. I'm way to sloppy to relentlessly hit such tight orbits, so haven't had such a collision.