Well. Neal. That was fun. Thanks
Space Elevator
131–140 of 216 posts
Re: Space Elevator
#132Earlier quoted context omitted.
That is mostly because the international space community works with metric, so the Karman line is at 100km above earth, and converting to imperial units would be forced. Remember, there are only three countries that use imperial units; two third-world counties, and a global superpower.
That’s not entirely true. The UK and Australia use Imperial measurements quite frequently, especially for speed.
hi, i’m australian, the only time i ever use imperial is if i work with hydraulic hoses or (rarely) tell someone my height
we pretty much only use metric, unlike the uk
Re: Space Elevator
#133Couple of things I learned from this: 1. Some birds go really high into the sky. Not sure how they evolved to tolerate such a hostile environment. But it seems that Duck-like birds are able to handle very high altitude. 2. There are lots of cool spaceships that man has made. But it seems most of these were made in the 1950-1990 era. It's a shame that we are no longer doing that.
List of cool spaceships being worked on now or recently: * The Falcon 9, the first partially reusable spaceship that actually costs less than not re-using anything * Terran R - a fully reusable space ship in the works by relativity space * RocketLab Electron - an active rocket that is unique in its use of electric turbo pumps, 3d printed engines, and advanced composites use * RocketLab Neutron - in the works, a large…
> * The Falcon 9, the first partially reusable spaceship that actually costs less than not re-using anything
We don't really know that. This _appears_ to be the case but the accounting is strange. We would probably get better numbers if the company was publicly traded.
I really like the RocketLab designs.
Where's the funding for Skylon? Some US company with deeper pockets should license the design (the heat exchangers are incredible)
Re: Space Elevator
#134Earlier quoted context omitted.
Just the opposite. This is engineer-driven testing.
[flagged]
Yeah. It's one thing to blow up during test firings, or when trying completely novel maneuvers like the belly flop.
It's another thing entirely to do that during stage separation. Sure, historically separation has been risky, but it's nothing novel. They didn't seem to expect the vehicle to survive past that anyways.
There would be a delay even if another vehicle was ready to go - the launch site is a wreck.
Re: Space Elevator
#135Earlier quoted context omitted.
but do you need to reach geostationary? couldn't you just switch to a rocket at this stage? Maybe a small one to bridge the gap? I would have thought that the first kilometres are the ones where you have to invest the most work so if you just bridge them using the space elevator it would be still an improvement. Maybe for cargo the 20 days are not really important
Getting to 100km or even 200km is easy. Staying there is hard. 80% of the energy in a rocket goes to adding sideways motion. An elevator upto GEO adds enough energy (taken from the earths rotational energy) to your payload to get it into orbit. If you let go lower down you need to add sideways velocity. In LEO you on an elevator would be travelling about 1,400mph and need to get to 18,000 to get into orbit. Sure ther…
> 80% of the energy in a rocket goes to adding sideways motion.
I have not researched this at all, so I'm not doubting you, but doesn't most of the energy go into accelerating the remaining fuel? So, by the rocket equation, shouldn't you be way ahead of the game by starting at the edge of space?
Re: Space Elevator
#136Couple of things I learned from this: 1. Some birds go really high into the sky. Not sure how they evolved to tolerate such a hostile environment. But it seems that Duck-like birds are able to handle very high altitude. 2. There are lots of cool spaceships that man has made. But it seems most of these were made in the 1950-1990 era. It's a shame that we are no longer doing that.
Regarding 1, wikipedia about Rüppell's vulture (highest-flying bird) explains the adaptation:
"The birds have a specialized variant of the hemoglobin alphaD subunit; this protein has a great affinity for oxygen, which allows the species to absorb oxygen efficiently despite the low partial pressure in the upper troposphere. A Rüppell's vulture was confirmed to have been ingested by a jet engine of an airplane flying over Abidjan, Ivory Coast on 29 November 1973 at an altitude of 11,300 m (37,000 ft)."
https://en.wikipedia.org/wiki/R%C3%BCppell%27s_vulture
Re: Space Elevator
#137I’m a simple hacker news lurker. When I see a post that links to Neal.Fun I click. Always such high quality work
Me too! They are always great.
Re: Space Elevator
#138Earlier quoted context omitted.
The structure wouldn't be able to passively stay together. If it was to be destroyed then it would burn up in the atmosphere like anything else. It is not made of a magic non-existent material that is infinitely strong. Of course if you had a massive dense asteroid attached that would not, so it makes sense to be careful with what is around it. But the orbital ring itself would break up and be no more dangerous than…
I'm more concerned about what's already within our atmosphere and isn't going to burn up. That's a lot of kinetic energy, and nobody says it's going to destroy the Earth, I said it would be devastating. You're forgetting religious extremists and countless suicide bombers.
Assuming the cable is rated for the sudden force changes and won't get split into a whole bunch of smaller pieces that will drop at just their terminal velocities. Think a shower of cable pieces rather than a whip. Not great, but it's likely that most of the energy will be dissipated by the atmosphere.
Re: Space Elevator
#139Earlier quoted context omitted.
And so what about the downsides? The ultimate target for terrorists. If that comes down and it wraps itself around the Earth, it'll be devastating.
The structure wouldn't be able to passively stay together. If it was to be destroyed then it would burn up in the atmosphere like anything else. It is not made of a magic non-existent material that is infinitely strong. Of course if you had a massive dense asteroid attached that would not, so it makes sense to be careful with what is around it. But the orbital ring itself would break up and be no more dangerous than…
To the extent that an elevator would represent both the power and interests of whatever rich entity had managed to construct it, it would be a target for those who want to reduce the power and harm the interests of that entity.
Re: Space Elevator
#140Earlier quoted context omitted.
but do you need to reach geostationary? couldn't you just switch to a rocket at this stage? Maybe a small one to bridge the gap? I would have thought that the first kilometres are the ones where you have to invest the most work so if you just bridge them using the space elevator it would be still an improvement. Maybe for cargo the 20 days are not really important
Getting to 100km or even 200km is easy. Staying there is hard. 80% of the energy in a rocket goes to adding sideways motion. An elevator upto GEO adds enough energy (taken from the earths rotational energy) to your payload to get it into orbit. If you let go lower down you need to add sideways velocity. In LEO you on an elevator would be travelling about 1,400mph and need to get to 18,000 to get into orbit. Sure ther…
> In LEO you on an elevator would be travelling about 1,400mph
That's a pretty significant speed already and it helps that you are already in space. See how tiny a Pegasus rocket is, and that one is launched from aircraft, slower, and nowhere near as high as what we are discussing.
https://www.northropgrumman.com/space/pegasus-rocket/
Getting to 100km from ground requires beefy first (even second) stages because you need to accelerate further stages plus the fuel, inside the atmosphere. We can basically pretend we are starting at the second or third stages. It now up to the rocket equation.
So, to recap, there's already 1400mph of sideways motion, at a negligible air resistance, 100 to 200km up with vacuum optimized nozzles. It is a massive win.
The question is if we could hoist what are still relatively heavy payloads.