Re:The Launch Landscape: Small Rockets
by throwaway69123 on Monday June 28, 2021 @07:00PM
(#27669417)
Excuse me but I really appreciate your replies, so my reading of what your saying is the launch is less about reaching a height but instead reaching a velocity that can escape earth’s gravity and launching from a higher altitude just decreases the distance the rocket has time to reach this speed?
Re:The Launch Landscape: Small Rockets
by SonicScrub on Monday June 28, 2021 @09:12PM
(#27670481)
Things in orbit like satellites and the moon have not escaped earth's gravity at all. There's lots of gravity in orbit. Being in orbit is when the centripetal force from an object's tangential velocity matches the force of gravity. In other words, get thrown so fast that the arc of your trajectory continually misses the Earth as the surface curves away from you.
The only reason why you need to go up at all is the pesky atmosphere works to slow you down, making it difficult to maintain such high speeds. Satellites have to be up high enough that drag becomes less of an issue. If it weren't for the atmosphere, you could achieve orbit 10 feet off the ground if you moved fast enough.
Re:The Launch Landscape: Small Rockets
by gremlinsinc on Monday June 28, 2021 @01:52PM
(#27665113)
What about vertical launch from 10k feet up, or even higher on a mountain or something, would that provide a better energy savings?
Re:The Launch Landscape: Small Rockets
by SonicScrub on Monday June 28, 2021 @02:00PM
(#27665236)
That savings has to be worth the building of expensive infrastructure at altitude, which is unlikely to happen. Air density at 10k feet yields is only 25% less than sea-level, so you're not going to see substantial performance gains. It's much better to focus efforts on choosing a launch location as close to the equator as possible where you can shoot due East (to take advantage of Earth's rotation) without flying over-top of people. This will yield much greater energy savings. There's a good reason why the world's launch locations are where they are.
Re:The Launch Landscape: Small Rockets
by gameswithgo on Monday June 28, 2021 @04:24PM
(#27667533)
you get more savings being near the equator than being high. if you can manage both you get a very small win that might not be worth it if you are far from infrastructure. better to add a little more fuel than make the satellite get shipped to your remote equatorial mountain
As for a balloon launch, well, balloons have absolutely dismal maximum payloads, so there's no way you're going to be able to hoist a vehicle with enough propellant to reach upwards of 7 km/s underneath a balloon.