Leo Wandersleb on Nostr: Rockets expend about 20% of their fuel just to get out of the thick atmosphere. TIL ...
Rockets expend about 20% of their fuel just to get out of the thick atmosphere.
TIL there was/is a company that tried to glide all the way to space ...
Two weeks ago, I had explored how to get to the edge of space with lighter-than-air vehicles:
I learned so much about rocket science exploring the idea of a 30km high "zeppelin" or blimp ... but got attacked viciously on reddit's r/askEngineers and r/rocketry:
https://www.reddit.com/r/AskEngineers/comments/1g700qg/why_are_heavy_lifter_rockets_not_launched_from/ (OP got deleted)
https://www.reddit.com/r/rocketry/comments/1g7qwug/how_much_would_access_to_space_improve_if_we_had/
But I learned that the biggest of rockets have virtually no drag loss but they still have a loss from atmospheric launches called gravity "loss" which comes from the fact that in the initial phase, the rocket has to go up and not sideways while sideways is what you need to get orbital speed. The flatter it accelerates, the more it accelerates in the right direction. That loss is easily 20% of the total budget to low earth orbit. Given that payload makes up only 4% of the total "wet" mass of a rocket, that's a big deal and I still believe, building a 30km high platform held in place by tethers to launch heavy lifter rockets is an idea worth exploring.
Anyway, today I found out there was a company that went even one step further. At 30km, the rocket would still have to start at an angle and could not use ion thrusters from the start Ion thrusters would allow higher top speeds with the same amount of fuel. That company - http://www.jpaerospace.com suggested a platform 42km high with the space ship being a giant, lighter than air mono wing that would gently accelerate and climb from there all the way to orbit. And they did not stop at reddit posts. They did build some small scale models but it looks more like rudimentary hobby scientist builds than the future of space travel.
TIL there was/is a company that tried to glide all the way to space ...
Two weeks ago, I had explored how to get to the edge of space with lighter-than-air vehicles:
quoting nevent1q…4nuaIn an interview, Elon Musk recently said that Earth has just the right gravity at which space travel [with chemical rockets] is theoretically possible. A bit less gravity and it would be easy. A bit more and it would be impossible.
I'm not sure what the limit would be but the fact that we have enough in the tank to do a propelled landing tells me there is still some margin. But not much, as much of the breaking before landing is done by air friction.
So while a bit bigger planet would not be able to land as smoothly, a much bigger planet basically needs nuclear propulsion to get off the ground.
So what are the actual limits here? Earth invented life and went through snowball times and global extinction events. Bigger planets' intelligent life cannot get off their surface - or might not have a solid surface at all that's not covered by liquid hydrogen. Could intelligent life develop on a gas giant? If so, what would be the hurdles to even communicate out? How would one go about sending a radio signal from Jupiter? Would life on Jupiter even come up with radio technology given it's probably useless on their planet? Or can more complex molecules not develop at all on gas giants?
In the other extreme, smaller planets, getting to space is "easy" but getting to life or intelligent life probably not. With less of an atmosphere, comets are more frequent to hit the surface. It needs less rock for "global" events.
I don't understand enough about the origins of life to rule out non-carbon based chemistry but I would find it hard to believe life to spring into existence on a planet that has no liquid for chemistry to happen in.
I learned so much about rocket science exploring the idea of a 30km high "zeppelin" or blimp ... but got attacked viciously on reddit's r/askEngineers and r/rocketry:
https://www.reddit.com/r/AskEngineers/comments/1g700qg/why_are_heavy_lifter_rockets_not_launched_from/ (OP got deleted)
https://www.reddit.com/r/rocketry/comments/1g7qwug/how_much_would_access_to_space_improve_if_we_had/
But I learned that the biggest of rockets have virtually no drag loss but they still have a loss from atmospheric launches called gravity "loss" which comes from the fact that in the initial phase, the rocket has to go up and not sideways while sideways is what you need to get orbital speed. The flatter it accelerates, the more it accelerates in the right direction. That loss is easily 20% of the total budget to low earth orbit. Given that payload makes up only 4% of the total "wet" mass of a rocket, that's a big deal and I still believe, building a 30km high platform held in place by tethers to launch heavy lifter rockets is an idea worth exploring.
Anyway, today I found out there was a company that went even one step further. At 30km, the rocket would still have to start at an angle and could not use ion thrusters from the start Ion thrusters would allow higher top speeds with the same amount of fuel. That company - http://www.jpaerospace.com suggested a platform 42km high with the space ship being a giant, lighter than air mono wing that would gently accelerate and climb from there all the way to orbit. And they did not stop at reddit posts. They did build some small scale models but it looks more like rudimentary hobby scientist builds than the future of space travel.