ment18

They should be able to do something like skylon, a huge horizontal landing spaceplane running on hydrolox. Use vacuum expanded engine like ssme, and no airbreathing. Something like 20t dry, 10t payload, 220t prop. Mid air topping up of props would be fun.

If your rover could go significantly faster, it would get rid of a lot of problems. Moon rotates relatively slowly, so you could spend 24 hours inspecting, then 12 hours catching back up if you can go 30 mph.

Unfortunately, it was GTO-2277. https://www.reddit.com/r/spacex/wiki/launches/gto_performance

Nuclear lightbulb is feasible, they had tested the quartz that the bulb was made of. Your statement about methane ntrs is completely false. In a normal solid core you still get 650s isp, about 200 more then hydrolox. You get a high density propellant that can actually be stored for long duration missions. It requires less water, which and is the main limit for Martian ISRU. The exhaust of a solid core engine is not radioactive. Nearly all nuclear engines info I've seen has very good atmospheric isp, usually like 80% of vacuum, which is better then hydrolox. Shutting down these engines are all relatively simple. Insert control rods, then taper off the flow of propellant as the engine cools. Simple math problem. And spacex already has a nuclear project, it might not have nuclear material yet though. A nuclear powered methane BFS could ssto 100t to leo with the same hull shape.

Your right, real engines cannot arbitrarily reduce their thrust. Most engines can throttle a little bit, like +-5% I think, but it takes special engine designs to get higher than that. The Apollo landing engine was unique in its ability to throttle to 11% I think, and Be4 and Merlin can throttle down to 40% and 70% if I remember correctly.

Laser launch allows you to ignore many of the difficult parts of putting things in orbit. It allows you to have nearly infinite power without much mass on you vehicle. The huge infrastructure things like mass drivers and tethers are limited on where they can launch vehicles by inclination and distant targets need their own launchers. Laser can be used for nearly everything, ex starshot.

Its ridiculous how society is willing to accept thousands of deaths in many areas, but none in space travel.

I actually did a SRB propulsive landing in KSP for the laughs. I just gave the landing thrusters a certain amount of deltaV that I thought would be enough, and then tweaked that deltaV by removing and adding more thrusters (sepatrons). I used KOS to trigger the thrusters at a very specific height from the ground, which I tweaked until it worked properly. I eventually got it to work, though the engine burned a little too long and it jumped after touchdown, non-destructively. Here is the video.

-Martian Atmosphere 95% CO2, its super thin to begin with -Methane and LOX have very similar temp ranges (methane freezes at -182 and LOX boils at -183, tanks do not need to be badly insulated from each other.) They already have to be cryogenic for LOX -Better ISP, I can't find good number but Methalox is probably 20 or 30s better then ammolox. -Not using hydrogen in long duration spaceflight, tri-propellant engines are not easy. -Can ammonia do autogenous pressurization? -Why would you want hydrazine. The point is to have as few propellants as possible. Make everything simple. -It just has lower performance. WW2 jet propellants are garbage specific impulse. Everything is super mass limited, need maximum mass efficiency from propellant. -Methane cars exists, it is easy rover fuel, a specific CO/O2 engine would far outperform any other propellant combo on Mars surface. Nobody even cares about reactors on rovers between fuel cells and batteries. -Already have to do electrolysis to get hydrogen, the water is easily dealt with.

Based on the wiki page you linked, each pair of solar arrays and associated stuff is about 16t. There are 4 of them total on the ISS, which produces about 120kw, so 30kw per pair. This means that the solar is actually around 500kg/kw. And as you pointed out the ISS solar arrays are old and not very mass efficient. Those 16t figures includes a lot of extra junk, like radiators and batteries, so the figures are much better for solar in reality. Edit: The batteries per truss weight about 4t. So more like 400kg/kw. https://www.nasaspaceflight.com/2017/01/spacewalkers-upgrading-iss-batteries/ (48/4) * 335 = 4t This paper claims 10kg/kw currently exists https://digitalcommons.usu.edu/cgi/viewcontent.cgi?referer=https://www.google.com/&httpsredir=1&article=1941&context=smallsat

They shrank the design because it was too costly to create a 12m rocket, but 9m was much less expensive. There is the possibility that ITS scale vehicle is still planned, just after the BFR, sorta like falcon 9 v1 to v1.1. BFR is nothing like the space shuttle, like nothing at all. They serve completely different purposes and have completely different designs. BFR doesn't have wings, it has control surfaces. BFR is for interplanetary travel, not orbital maintenance. BFR is composite, not aluminum, runs on completely different propellants, with completely different engines. The shuttle had no propellant tanks, and the BFS itself has more propellant storage than the orange tank (by mass). BFR heavy is not going to happen. SpaceX has learned from the FH, and the forces don't make sense. BFB is designed for very specific force loads, straight through the bottom, so the side forces from other boosters would be very bad. Require complete redesign of core, much worse then Falcon 9 because carbon fiber is a pain with how it responds to forces. If you can't break you payload into 150 ton pieces, thats ridiculous. We have created the ISS out of <30t parts.

Osprey was also massively over budget and behind schedule.

The only remotely similar engines are rd-0120 and rs 68, rd-0120 won't be used for political reasons, and the rs 68 would incur very large payload loss due to terrible Isp and large mass (would work*). No engine even comes close to meeting their requirements, maybe because those requirements necessitated the most complicated engine ever made.

Honestly, not really. When you want to launch multiple times per day, you don't have a choice. A conventional launch system will not evolve to that need within a reasonable time. In addition, these rockets are huge, so the locations where land based launch sites can be is super limited. Boca Chica is limited to only F9 and FH, 12 per year. Not even close to BFR, and there are people too close to it to launch BFR. In addition, how are you going to get approval for landing the BFS at a land based site, it cones from orbit without glide capability, it could miss and hit populated areas. Also, they dont have to go far, only 10-20 miles off shore and launches won't be heard from shore. It allows you to choose your launch inclination as well. There is a huge difference between current rockets where you need to ship in all of the parts of the rocket and the BFR, where the only thing you need it prop (tanker or on site creation), and payload, which is usually prop anyway.

Wasn't there an issue in the skylab era where they found that people couldn't work very well in wet labs?

I think spacex is planning to use sea based launch platforms soon, before P2P. These are listed under Launch Engineering: http://www.spacex.com/careers/position/215429 - Literally Called Naval/Marine Architect http://www.spacex.com/careers/position/215424 - Experience with shipyard work, experience as ship engineer http://www.spacex.com/careers/position/215307 - More maritime experience, shipyard I haven't looked through the whole catalog, but I doubt these are the only ones.

Nope: Katelyn M. Cooper, Anna Krieg, and Sara E. Brownell Not really, this is more quantifying the self-concept different between men and women.

Can you explain this? Lower total mass should help first stage, and more engines on the 2nd stage, depending on gimbal, could allow for some sort of engine out, maybe only later in the burn.

I'm confused by the drastic decrease in 2nd stage thrust.

Generally, any engine that doesn't use up nuclear material is safe. For example, if an engine converts enriched uranium to depleted uranium its ok, but if the uranium just disappears then it probably spews nuclear material and is considered unsafe. Nuclear material can be a variety of things such as deuterium, tritium, plutonium, uranium, thorium etc.

350*9.8*ln((115+4.5 + 60/4.5+60) = 3768m/s. You need to refuel the stage in orbit, which is pretty difficult. You can only get about 70t of propellant into orbit with an empty falcon heavy launch.

https://en.wikipedia.org/wiki/Project_Mogul Was balloons that were intended to spy on the USSR. Explains the extreme secrecy. I think they were designed to be radar resistant, which make their design very strange, like f117, which further developed the rumors.

Mass Market Reusable Launch Vehicles

Yeah, your right. Since one can actually ISRU oxygen from the moon pretty easily (energy expensive, but rocks have lots of oxygen in them), hydrolox is >80% oxygen, so if you carry hydrogen for your entire trip and fill up oxygen on the moon, you can get a pretty good payload fraction. https://curator.jsc.nasa.gov/lunar/lnews/lnmar97/oxygen.htm

I think that is will be a methalox rocket similar in scale to the ITS (so 300t to orbit), but optimized for lunar operations rather than mars. It will have a much lower designed payload fraction than ITS/BFR, since the deltaV budget for the Moon is much worse then Mars. It might have an over-sized methane tank, so that it can do partial ISRU, and oxygen takes up over 70% of the propellant mass anyway. Also a Be5 engine that is ffsc, probably slightly lower efficiency than Raptor since BO likes to take a less stressful engine design philosophy. Definitely Methalox so that space travel has a common propellant, they are already using lng. Probably a much more lift oriented design than ITS, larger wings on ship that actually serve major role, and some on the booster.