wumpus

The above are the only crewed combat spacecraft. There have been plenty otherwise (for various degrees of "flown"). The V2 could achieve ~200km altitude (should qualify as spacecraft) if launched vertically but for long range use could only get 88km (not spacecraft). No idea if any where launched from close enough to their target to break the Karman line. There were also thousands of ICBMs deployed, but none so far has been launched armed (and presumably never tested with actual warheads). There have been at least two successful tests of anti-satellite weapons. I'd be shocked silly if there weren't plenty more orbiting the Earth.

Convert your craft to "N" ships flying in formation where "N" is the number of cores you want to use? As mentioned above, this is entirely a unity thing and unity just started using parallel threads with 5.0 or so. I'm not even sure my suggestion will work: KSP tends to model actual vessels as multiple parts flying in close formation (and handle physics individually), it is quite possible that Unity wouldn't figure out that it could split each into a separate thread (or might not be able to due to subtle physics interactions. Flames can interfere with other spacecraft (RCS doesn't).

I suspect it would be easier to simply launch someplace without weather. Mojave and Vandenberg should come close for the US, but I'd probably build in the middle of a desert known for low winds if it was all that critical (and in the end it probably isn't worth it). I also rather doubt you can really get a good launch over ocean from any constant-weather location [anywhere in the Australian outback with an unpopulated channel east to the ocean?]. Orbital (and Stratolaunch if you want to pay big bucks for more than a few tons to LEO) appears to have the answer right now (especially if you can re-adjust your window after moving the plane to somewhere that has sufficiently friendly weather). Orbital only gets a flight every few years on Pegasus, and Stratolaunch's outlook is far more bleak.

I still favor Ecuador, although you need to vastly more careful about where the stages come down.

Just as long as he doesn't block Van Gogh's view. Looks like this is what he was trying to paint.

With 10% of the payload, for the "paper rocket". Unless the Air Force project manager decides to throw even goofier requirements to the project than wings. The interesting bit of the project is similar to what DC-X is said to have pioneered: launching fast and cheap (although I suspect that the ~100 (wasn't it 99?) suborbital flights of the X-15 were wildly cheaper than any other manned rocket. And neither DC-X nor this were manned).

The Shuttle had a glide ratio of 4:1 [i.e. a brick] on those redonkulously massive wings. Presumably there were reasons you couldn't use X-15 style wings (they worked fine at mach 4. For mach 14 you might need shuttle wings). I'd have to wonder if a few fins or maybe a more elliptical booster could allow a glide ratio of at least 1:1 (although I wouldn't be surprised if falcon can do that on its own). At that point you have cut your terminal velocity (and thus your final suicide delta-v) in half.

About as likely as this:https://en.wikipedia.org/wiki/Saturn_C-3 (or on video) https://www.youtube.com/watch?v=PetUQPu1wTA [vintage space] Although I've called this the "Apollo Launch System" and would expect it to be as political as the SLS (since the whole idea of both was to reuse/maintain the infrastructure and the jobs involved). It looks good, but I really don't expect the "Apollo recovery" to really work.

I think there's a mod that can make Al-based fuel out of the Mun (or Moon in RSS). This is somewhat more realistic (I think the chemistry has been studied for a proof of concept), except you get lousy Isp. The Isp really doesn't matter so much since you only need enough delta-v to get off the Moon, and then you simply accept that you will have a lot of mass on your ship. If you can keep hydrogen in its tank (non-trivial), all you need is an oxidizer. The low mass of hydrogen makes it an ISRU favorite (you aren't going to find an oxidizer with a similar low mass [unless hydrogen can act as an oxidizer, that wouldn't surprise me].

Worked together? Political will and a pile of bucks? You would start with something like Orion, and then work up. You would likely want to launch a fleet of ion [insert high-Isp motor of your choice] powered craft to herd some asteroids into Earth orbit for raw materials, this would drastically change the scope we could work with [not to mention what happens when you suddenly crash the price of platinum for use as catalysts]. Remember, Orion works using nothing more than pre-Apollo tech, although launching from Antartica might pose problems (but would make a good symbolic place for the world to work together). We could build it now, with just the bucks and the political green light.

This is pretty much a standard circuit called a DC-DC converter (up or down). Typically 80% efficiency, you can get a bit over 90% if your load is known (and constant) and you are willing to sweat a bit (pretty much mandatory for any space application). The output isn't even all that choppy (assuming a less naive design) even before the capacitor filtering. Look up the design of any switching power supply to get the basics.

Comments in red because I couldn't figure out how to break up the quote block. Started out well, but the snark fell into trolling toward the end (when you ran out of "marketing/PR" to puncture).

Sooner or later I will trip up and say "have a nominal trip" to a non space nerd.

Interesting (and a long, long, way from space). I suspect the ability to quickly quench the reaction (assuming it can, I only did a quick read through and lack the nuclear physics to know) would be the most valuable feature (compared to other nuclear rockets). Note that hydrogen's wonderfullness as a fuel tends to decrease after escaping Earth's gravity well. That stuff simply doesn't like staying in the fuel tank.

Odd. I wouldn't be at all surprised if 30 Proton engines could be reliably started together. I'd even be trying to decide which would be worse: 60 turbopumps or dealing with pressure-fed hypergolics. Mostly this would depend on just how much delta-v I could get out of the "0.2 stage" pressure fed stage and simplification to a 10? 20? 5? engine 1.2 stage.

I clicked the link thinking about a toy from my youth [1970s, although I think the toy dates from the 1960s]. I'm guessing it was the same tech as a supersoaker only pointed down (I don't recall trying to use one as a water pistol, then again it would be hard to fire and there was no throttle). I think there was a more expensive model with a standard (small) rocket and a larger first stage. I suspect when the water pressure of the base dropped enough below the water pressure of the top stage, a spring released and launched the top stage. Don't expect the thing to go too high. The only thing slowing down the flight down was the angled rear fins that made the thing spin on the way up/down.

At that point you needn't bother looking for the guy in the suit: aim for the white-hot rifle and the guy firing it will be nearby. If you have time before they shooting starts, you still have time to find the [presumably optimal] guys in the marketing pictures.

The last group that maximized computer density by limiting wires was likely Seymour Cray (and whatever computer company he was at). Even then, cooling was the critical element, and wildly moreso now that nvidia is producing 300W GPUs for supercomputing (yours for $15k a pop). SRAM vs. DRAM. Modern computers are based on a memory hierarchy: SRAM (small SRAM areas burning the most Watts) are fastest (~1ns) followed by larger SRAM areas (~10?ns) [and typically two levels of SRAM with different speeds], followed by DRAM [~50ns], followed by NAND flash [10,000ns?] followed by rotating discs [10,000,000ns?]. The idea is that as the speeds get slower and slower, you have to read less often (and typically need larger batches. Everything from L1 [~1ns] to DRAM and below is read in batches of 64bytes a pop, everything above that has issues reading less than 4k bytes a pop. And of course cost varies with price (except your fastest SRAM slows down if you make it bigger. You can't have a large two-cycle L1 at any price). 3d memory is here, for values of NAND Flash (I think 64 layers is shipping). Intel's 3dXpoint sounded like an attempt to barge in between DRAM and NAND flash (changing DRAM to something like a cache in HBM form, and turning NAND into a commodity). Until they get the endurance they were claiming no more than a year ago, it isn't going to happen. Don't forget that programming a computer made out of many processors is tricky [wild understatement] (notice that after the Unity upgrade and everything else, KSP largely uses only one CPU?). You can trivially make a computer fast by slapping lots of processors together, and this has been true since the late 1980s. Software techniques are slow to build up to use such a bounty.

Silly Falcon Heavy idea: Aluminum carrot. Preferably launched to Mars.

I'd go so far as to say it is absolutely necessary for any near-term Mars expedition. This even includes nuclear rockets as the hydrogen they used going from Mars to Earth will leak out for the return journey (and hopefully CO is good enough for the way back). It is absolutely insane for an 8 year program (although presumably the ISRU would land in the "test run"). Since the 4/8 year window is essentially tied to NASA funding, are there any other potential windows that it might be possible in? Any idea what tech needs to be in place to make this happen? Inflateable habitats (if only for the trip there and back again): don't underestimate this. A huge chunk of delta-v goes into moving the habitat and you can't cram a crew into a Dragon for 2 months. ISRU: I'm guessing this is mostly a straightforward chemical engineering challenge, only with restrictions (mass, mass, radiation hardening?, mass) that few chemical engineers consider. heavy lift: Presumably Elon Musk will have the Raptor plans/budget in his back pocket every time he is near NASA or DC. I'd expect such things to be possible (with Kennedy-style budgets) with Falcon Heavy, Delta Heavy, or SLS. propellants: hydrogen storage: hopefully the James Webb Telescope will confirm a few things about zero-boiloff cryosystems, but hydrogen will still leak out. nuclear space systems: good luck. I have to wonder what kind of results you can get from a somewhat upgraded NTG (i.e. a low-level reactor that is nowhere near critical and expected to produce power at a level on the order of the ISS solar panels). Needed for ion power, VASIMR, and similar (note VASIMR has addition issues like hydrogen storage, ion systems won't fit in the timeframe). I'm sure there is a ton of tech needed, but these are the ones that wildly inflate the price tag if the aren't ready.

But that was never the point. Unity was fine for what Harvester announced on the Orbital forums. Unity wasn't enough once they added the solar system. And if you look at the original statement, I suggested that using Unity was likely *still* the right decision as they were able to kludge the Unity physics into "close enough" (but don't ask the principia guys about it). Software isn't a single unchanging block. The needs that the software started with aren't the needs it has now, even though it is tied to the decisions of the past.

It could simulate the physics of a rocket burn quite well. Interplanetary trajectories, not so well. Two separate issues.

"Supported all the physics necessary for rocket simulation" isn't quite true and has bitten him (and successors) more than a few times. The catch was that it could simulate rockets quite well, but since it is stuck in 32-bit (single floats, no relation to the "64 bit" edition that simply allows more memory in use) mode it doesn't work well at interplanetary scales (see the Kraken and how it was slain). Harvester didn't design KSP with anything like .18 in mind (he certainly didn't plan on having a solar system, and probably not even a Mun to visit). Had he thought it would turn into something like that, he might not have gotten started (he'd be still hacking away at the double precision physics engine). When he first posted on the Orbital forums, he was expecting it to remain 2-d... Don't underestimate the power of working code. The goal is to keep the code working, not to start out with "perfect" code.

Have you played KSP at all? [Even the demo version will teach you this, just ignore the lessons of spaceplanes outside of realism overhaul (they basically break the game thanks to the toy size of Kerbin)]. Most of what they say is likely technically true, but pointless. Getting into orbit is an exercise in speed, not altitude. A rocket that burns out 90% of its fuel in the first 10km is burning the fuel in a goal to get that speed, not to get to 10k. The two other reasons it could happen: 1. It is typically cheaper to extend the fuel tanks than to make a more powerful engine. This means many rockets will leave the pad with a TWR of 1.1 to 1.2, meaning the rocket is hideously inefficient [in terms of fuel. It is still a smart design] when it launches. About the only efficient way to add power (and later throttle down if applicable) is to use solid rocket motors (typically strapped to the sides). 2. Extra small rockets suffer aero losses disproportionate to larger rockets (effectively aero efficiency scales with length of a booster). For any rocket that can be carried with by an airplane (even the big boys like An-255 and Stratolaunch) expect aero significant losses compared to something the size of a Soyuz. Mostly, this all depends on how easy it is to modify the An-255. Orbital got its start this way (it started with a B-52 which was designed to drop bombs and they could use some of NASA's designs for dropping the X-15). Statolaunch is effectively dead (it costs billions to design a modern jetliner, don't expect Stratolaunch to be much cheaper) and there's no real way to recoup the costs.

At least one GSO satellite has been looped around the Moon after getting into the wrong position after the initial burn. Read about it roughly before 2000. Not sure how much that limited its lifespan by using up so much stationkeeping fuel. I can't help but think it would be a lot cheaper (R&D wise) to simply add solid boosters. Especially if 1.0 was designed with becoming falcon heavy in mind (of course considering how cash strapped they were when designing it, my guess was that heavy came along with 1.1 (I had no idea that 1.0 was essentially limited to launching dragon 1.0).