wumpus

You are asking to terraform a planet that essentially doesn't require terraforming. Perhaps something like Venus, only with available hydrogen? And if there is liquid water and carbon, does the planet already sustain life and do you plan on keeping that life around post-terraform? I'd insist that Venus should be ideal for terraforming, just expect it to take a long time between seeding the clouds with genetically engineered life (designed to slowly convert Venus's clouds to something more friendly). Granted, getting life to deal with a lack of magnetic field (and Van Allen belts) might make Venus a no go.

To be honest, Blue Origin still hasn't had a crewed launch into space, and hasn't launched anything into orbit. They do have some real contracts to produce real engines with real milestones (don't expect to slide by those contracts with just powerpoint), but they've never launched anything that Virgin Galactic hasn't (or Virgin Orbital, for that matter). [there might be some trolling about the exact height of the Kármán Line]

True, but trying to retrofit a re-entry shield, a landing maneuvering system, a braking scheme (on a spacecraft presumably designed with vacuum engines) and landing legs is going to be tricky. The Shuttle was designed with all that (plus an ambitious cross-range bit) and only had one kg of cargo space left over for each 3-4 kg of dry mass to orbit. So far, the electron appears to be the only rocket so far to try to retrofit stage 1 recovery onto an existing rocket. We'll see if they launch one a second time.

Space elevators are in orbit. This is in space. Of course, building something "in space / viable orbit" on the Moon would be a lot easier. Build it on the highest mountain with a small extension and you are clear, not to mention the much lower orbital velocity.

The obvious issue is just how high you can built your rail, which defines just how fast you need to leave so drag losses leave you with orbital velocity when you leave the atmosphere. It is obviously far more doable in KSP, thanks to Kerbol having about 1/3 the orbital velocity of Earth. This is why spaceplanes work at all in KSP. You will, of course, need at least some propellant once you enter orbit (presumably after half an orbit) because your orbit will be elliptical and cross Kerbol and intersect roughly where your launch facility is. Raising Pe out of the atmosphere should require trivial amounts of propellant (probably less than the Shuttles OMS engines), but is absolutely required. Spinlaunch is the only group I've heard of trying to do such a thing. It gets discussed in this thread : The big catches are that the rocket (and payload) have to withstand 10k gs of lateral acceleration and they also have to build something that will stop a counterweight being flung with roughly the momentum of the rocket being launch to 1km/s. On Earth, some of the mountains of Ecuador should be ideal for this (they are further away from the center of the Earth than the Himalayas and are nearly on the Equator), but have fun with the local politics (not to mention getting Peru, Columbia, and Brazil to all agree for you to launch over them). I think China has a launch facility on the Tibetan Plateau (not used for the big, important flights. Presumably because the big boys barely notice the difference in drag) while the US never bothered to put a facility in Leadville, CO despite the proximity to Colorado Springs and the Air Force Academy.

So I guess it comes down to how much delta-v is in a "full day" of thrust, and how often you have to change the rods. Also the design of your reactor changes just how quickly you want to change those rods as the big boys used for power generation last much longer (one day sounds short for even plutonium production). I still think that the "single use set of rods" simplifies the design enough for serious consideration.

Even Spinlaunch is only trying to get a "first stage replacement": release at about mach 6 and only require vastly smaller engines and fuel. But the drag losses on that are still huge. But you might have a realistic railgun (no longer than 10-20km at least) if you don't try to get to orbital velocity on the surface of Earth. A much more plausible (but requires a lot of tech to be developed in parallel) would be to use a railgun to accelerate your spaceplane to supersonic speeds. Then use a scramjet to get to ~3km/s (maybe 4km/s by the time the tech is ready). Use traditional hydrolox for the rest. Staging is optional, and more likely if you limit your scramjets to ~2km/s (within current tech proof of concept: see the x-43). Most of the problems are discussed here:

I remain unconvinced that a driver willing to trust an autopilot is going to be much safer driving the car himself. For those wondering if regulators might clamp down on this thing, all they have to do is drive a loop around the Washington DC beltway to realize that humans (especially Marylanders, Virginians, and Washingtonians) should never be put in charge of a multi-ton vehicle at highway speeds with minimal training/oversight. Insurance companies may come down hard on the things. But I'd expect the existence of enough insurance companies with a long enough view to get the humans (or at least the worst of the lot) from behind the wheel.

Fair warning for anyone going through Virginia (I-95 from Washington DC to down south, also the highways to the main airport in/out of DC), the speed limit can be as high as 70mph. Going 80mph (regardless of the speed limit) is statutory reckless driving and can result in jail time and other nastiness. Google "speeding in Virginia" before continuing speeds high speeds past New Jersey (Maryland doesn't have such laws, but loves ticking out of state cars).

According to the infallible google, maximum speed of a Cessna 152 (cruising speed is maybe 5km less) is ~200km/h or 120mph. Or in rocket lingo: 55m/s.

Didn't the Saturn V lift off at something like .1g? Adding lots more fuel to the first stage is way cheaper than developing even more powerful engines, and increases delta-v a little. Saturn V also shut off an engine to avoid going over 3g, which for all I know is pretty standard with crewed rockets. There's a Japanese orbital rocket where the first 3 stages are all solid (so increasing thrust mostly requires thicker walls), that takes off at ~2.4g and the acceleration keeps increasing. This nearly eliminates gravity losses, but I don't know how much they lose through aero drag losses.

The SLS frankenrocket cost billions to redesign to fit. If you are going to build a frankenrocket, look to Orbital and their success with cobbling together surplus ICBMs and modified Pegasus final stages.

Even NASA/DoD would have a hard time getting Congress to let them have a contract like that with ULA (or similar). They'd then have to divide the launch capability between all sorts of competing departments, each demanding their hands held in different ways and having a whole slew of MIL-STD (or NASA/FAA) requirements to fill. Maybe ROSCOSMOS or a Chinese company could get such a contract, but I doubt it. So not only does the for-profit business not work that way in launching the spacecraft, nobody for-profit or not is willing to pay them just to "lift tonnage". Oddly enough, the DoD paid ULA a billion dollars a year to "launch nothing". You'd think that asking them to launch 10 "10 ton space-pods" (or some sort of space shipping container) would be a better deal. But the pork must flow.

"Korona SSTO will be back. Works are planned to restart at the beginning of the next year. In the new plan it will be 31 meters tall with launch mass up to 300 tons. It will be capable of delivering 13 tons to LEO with reuse possibility. (Official renders)" So, assuming that the 13 tons is mostly the ship, then you need an Isp of 292s. Certainly done many times before by Roscosmos (not sure about launch to vacuum), but just how much cargo is that 13 ton ship going to have? And if it is supposed to land and be reuseable, that is even less likely. For perspective, that's about twice the mass of the Soyuz spacecraft (the capsule, not the booster) and it has to have the main engines, propellant tanks, and guidance systems.

Magic: For when you want a reason for your spaceship to arrive at the precise time the plot requires. ("speed of plot" doesn't require magical drives, but it certainly helps with unspecified thrust & delta-v).

If this was KSP he could have just waited the 20 days to return to land (infinite air, water, and snacks). Possibly in 5 days with physics time warp. I've abused this plenty more times than getting out and pushing.

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I'm pretty sure the shock and vibe issues for a tank are significantly higher for the tank than the rocket engine (ok, *vibe* might be harder for the rocket engine with lots of nearby rocket engine and a significantly less sturdy vehicle, but shock requirements for the tank pretty much involve anything that doesn't immediately kill the crew). And such military applications require explicit specs (MIL-STD 810) and less formal tests, like when an Army reserve officer/mechanical engineer mentioned that they took his landmine detecting device (mounted in front of a tank) and proceeded to knock down enough trees to satisfy the tankers that it was strong enough. I worked for a company that made RADAR consoles for the Navy, and they had an internal required test (thanks to an unfortunate story staring the man who hired me) requiring the lead mechanical engineer stand on the bullnose (? whatever they called where the controls are).

I'm pretty sure it is a hard requirement in GSO. Especially if you have a lot of fixed antennae pointing at the thing. They get batted around by the moon, even if they don't need any prograde boosting.

That's mostly true, but the merlin engine was designed for Falcon [1], which they never really attempted to recover. Future plans for both Falcon [1] and Falcon 9 were based around parachutes. Oddly enough, the merlin engine doesn't appear to have had issues lighting while falling with air blasting into the nozzle while the raptor engine (which was designed with retropropulsion in mind) has crashed a few times thanks to failing to ignite while falling. Granted, we don't know what "plan C" was for recovering the rocket, and if it would work. Don't forget, "plan A" not only failed for recovering boosters (parachutes), it also failed for fairing recovery (catching it in nets). Plan B (fishing it out of the water) is working well enough that plan A was scrapped. So while you might claim that Spacex was "lucky" that merlins have a property that was never a design goal, recovery appears to be more due to a dogged insistence of solving the problem than pure luck. The original recovery plans wouldn't work (although presumably merlins *were* designed for long enough working life for reuse), and they simply kept at it. You shouldn't be surprised if some parts are eventually found to have the properties needed to solve the problem in *some* way (if not the original plan, i.e. parachutes).

I brought this up in the "using dirt for a NTR". Using water in a NTR will give you *less* Isp than hyrdolox, because hydrolox is typically run fuel rich for higher efficiency. Use anything heavier, and things get worse (CO2 will give you much lower Isp than kerolox). Also don't forget that turning off an NTR is non-trivial. The reactor will keep reacting, and thus still require cooling. So you have to keep pumping out propellant through your open loop cooling system at lower and lower temperature. And this all happens when your wet mass is lowest and you are expecting maximum return for your Isp, but not getting it. Simply ejecting the fuel rods (have several single use fuel rods) may be an option.

If it could work in a subsonic "jet" I'd expect them to have plenty of funding long before now. Mach 6 is pretty much only good for suborbital flight, either for transportation or as the first stage to orbit. Granted, mach 6 is plenty for orbital rockets. This certainly surprised me after learning some wrong lessons from KSP (sure, in theory you want to stage at roughly half the delta-v to orbit, but the engines for lift off are heavy, and there's little point in giving them more delta-v than you have to. And real propellant tanks are nowhere near as heavy as they are in KSP).

Even with Sabre, that would be difficult. The problem with SSTO is that approximately for every ton your SSTO can lift to orbit, a TSTO can be designed to do the same thing, and deliver the same tonnage to orbit. And by tonnage, I mean the SSTO payload, plus the mass of the SABRE engines, plus the mass of whatever fuel tank is needed for all that extra delta-v (note that while SABRE 'first stage' might have extreme Isp, it is hydrolox, and that means a fuel tank with volume issues). Officially, the secret sauce is the air/air cooling system for the intake air. Really, the "secret sauce" is the magic of the promise of a "spaceplane". That gets a lot of attention, but not enough money to really build anything but powerpoint.

The difference is that once you pass the Schwarzschild radius in a black hole, there are no known laws of physics to break. I'd have to agree with you that whatever laws are governed by such areas are unlikely to allow the magnetic car to work. It violates the law of conservation of momentum, instead of the law of conservation of energy. Slightly more plausible (especially knowing that mass isn't necessarily conserved), but still extremely unlikely. I like to point out when the EM drive comes up that an LED is perfectly capable of taking electricity in and producing a momentum out, much like the goal of the EM. It just doesn't produce nearly as much momentum as they want.

Sometimes these type of things serve as useful test articles. You design the thing in Solidworks and send the output to be made out of foam core instead of sheet metal (or whatever). Then the customer looks at it, requests a few changes, and you update your Soldiworks model. Finally you send the output to a machine shop to make the thing out of the "correct" material. The only problems that I can think of it was in the early days all work would stop as all the engineers would have to gather around and look at it. Later, there must have been some pretty big fights over whose kid gets this amazingly cool toy for their playroom (albeit probably one of the toys much cooler in retrospec than when you had it).