Earlier quoted context omitted.
It's NOT rocket science?
You can reach space using air breathing jets. You can’t stay in space using air breathing jets.
Didn’t Chuck Yeager burn his face off doing that?
Space Elevator
341–350 of 414 posts
Re: Space Elevator
#342Earlier quoted context omitted.
I don't understand why you think that where you put the base of a 35000km cable makes a difference for where the rest of it would fall. I also don't understand why you think that a 35000 km long cable falling in the ocean from space would cause any less damage to the planet than it falling down on solid ground, or at least why the difference would be significant.
> why you think that a 35000 km long cable falling in the ocean from space would cause any less damage to the planet than it falling down on solid ground They’re not obviously wrong. A lot of the cable is moving at escape and orbital velocities. Tensile strength is all that holds it together. If, as the cable fails, you sever the parts above from below around escape velocity, you’ll significantly reduce the length of…
Orbital and escape velocities??? The elevator is sitting over a stationary spot... it's moving at earth's rotational velocity. Only the portion above the GEO anchor is moving at orbital velocity.
Re: Space Elevator
#343Earlier quoted context omitted.
Aha, so in the stratosphere we should use oxygen / solid carbon boosters?
Their Isp is very low, unfortunately, because the molecular weight of the combustion gas is too high. Ditto for oxygen/carbon monoxide. Maybe the Isp could be increased by mixing in some helium, but helium is very expensive.
Methalox should suffice for practical and technical reasons?
Compensate the slight loss of ISP by using aerospiked rotating detonation engines...
Re: Space Elevator
#344Loved this site. Only thing I could think to add would be the ability to click each item and be taken to a wiki page or some further source of information about the object.
Re: Space Elevator
#345Earlier quoted context omitted.
This is where Douglas Adams was right, of course: > There is an art, it says, or rather, a knack to flying. The knack lies in learning how to throw yourself at the ground and miss. You're not going sideways - you're actively falling continuously, but somehow missing the ground for the entire length of your orbit.
Missing involves going sideways.
It could just involve falling long enough the the ground gets out of your way.
Re: Space Elevator
#346Very cool. One thing I wish was better shown: space is close, it's just hard to go up. Our liveable breathable atmosphere is razor thin compared to the size of earth. In most cases, 100km is less than the distance between sizeable metropolitan areas. It's a day long bike ride. Air runs out less than a bus ride across town. A 15k jog/hike would put you in the stratosphere. Those jet aircraft that seem so high are clos…
Likewise, it is crazy to me when I realised how thin our oceans are. I used to think of them as super deep (I mean, they are) but even the Mariana trench is a mere 0.2% of the Earth's radius. Average ocean depth is more like 0.05%.
We live at human scale within a thin slice of a planet-sized environment.
On the planetary scale, humans are tiny. We're more or less equivalent to bacteria.
Our entire civilisation is a skin rash.
Re: Space Elevator
#347Earlier quoted context omitted.
Energy for 1kg to reach LEO (800km * 1kg * 9.8m/s2) ~ 8MJ Energy to reach LEO velocity ~ (1/2 * 1kg * (8km/s)^2) ~ 32MJ
But the energy needed is not an indicator of what is difficult or dangerous. Leaving the atmosphere intact is the most difficult part of launching a rocket going by failure rate. Of those that reach space, those that still fail often took damage from the launch. Once you're in space, force over distance until your fuel runs out.
Failures rate is even less a suitable indicator. Going up 100km is achievable by a simple single stage solid fuel rocket. Going to orbit requires way way more complexity, including a giant first stage that can fail in atmosphere.
Re: Space Elevator
#348This is so fun
Re: Space Elevator
#349Earlier quoted context omitted.
Energy for 1kg to reach LEO (800km * 1kg * 9.8m/s2) ~ 8MJ Energy to reach LEO velocity ~ (1/2 * 1kg * (8km/s)^2) ~ 32MJ
The rocket fuel needed to produce that 40 MJ weighs close to 1 kg, especially when you include the oxidiser. So the energy needed to accelerate 1kg of payload to LEO velocity is much more.
That whole "tyranny of the rocket equation" thing is why I am surprised the actual first stage for launching a rocket is NOT a ground based reusable "up-chucker".
Basically, I would have thought that any momentum that can be imparted to the rocket before it has to rely on its self propulsion would be a huge help. Not talking about eliminating self propulsion, just an assist so the rocket could carry a larger payload or be smaller or whatever.
IE like a variation on Jules Verne's big gun for throwing the payload up there but engineered to be plausible and having the rocket still be self propelled. And safe.
But we don't seem to do this. So why?
Edit: First part of video [0]. Apparently it's not completely dumb. Just stupid-hard/impossible to do practically at the size required for big rockets and payloads. But small ones might work. Maybe.
Re: Space Elevator
#350I get it that it requires yet-impossible materials to build a space elevator that goes all the way to space, but what if we instead build one that only extends high enough to clear the thickest layers of atmosphere, so rockets could be launched from there for massive fuel savings?
The space elevator would need to be strong enough to lift a rocket. Though, maybe without all that extra fuel they could be much smaller and lighter.