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Indeed. As usual XKCD is helpful here. https://what-if.xkcd.com/58/ https://what-if.xkcd.com/58/ It's similar to why launching from a mountain top isn't worth
by simonh 4y ago
Indeed. As usual XKCD is helpful here.
https://what-if.xkcd.com/58/ https://what-if.xkcd.com/58/
It's similar to why launching from a mountain top isn't worth it. If you're launching to a few hundred km altitude, a 2km or even a 10km head start is peanuts. And altitude is only a small fraction of the problem, compared to orbital speeds large jet aircraft are barely even moving.
If you're launching anti-satelite missiles that's different. Getting altitude is the main aim, and military jets can get reasonably high with a small missile as payload.
- hoseja 4y agoThe major savings is in exponentially less air to go through, so you can do more aggressive gravity turn so you have less gravity losses. And he didn't even address the reentry questions, both of which are actually plausible - if you somehow have the fuel to drastically reduce your orbital velocity, you're suddenly no different than a sounding rocket, indeed not needing a heat shield. And if you cleverly slow down your reentry over many orbits, it can be very gentle.
- SonicScrub 4y agoThe benefits of the "exponentially less air" diminish once you have to slap an aerosurface on the vehicle (added weight + drag) to perform the pitch up maneuver Coupled with the fact that on deployment the vehicle is gaining velocity in the wrong direction until the engines ignite, accelerate forwards, and the vehicle begins the turn. The theoretical benefits of air launch quickly fade away given these practical realities. Nevermind the much more complex operations that comes with air launch. There's a reason why air launch has more or less died as an idea. The theoretical savings don't typically manifest once the additional complexities are accounted for.