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Comment by JulianMorrison | Hacker News Reader

1g at 1 atmosphere has disadvantages. Namely: to get off the planet, you will need a fully fuelled multistage rocket with an almost identical profile to rockets you'd launch from ground level on Earth. Something like a Falcon 9. That's a bit heavy to lug all the way from Earth.

Bonus: you have to launch by dropping it into a hell-cauldron of poison gases miles above a crushing, melting surface, better hope you don't have an engine out, because there are no launch aborts or do-overs. Then you have to fly it out through a hot corrosive acid atmosphere which I don't imagine would be very friendly to machined aluminum.

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Not quite an identical profile; it's not quite 1g, since Venus is less massive, and you're already quite a ways off the surface.

It's still not trivial, but it's not like there are a whole lot of do-overs when launching valuable human cargo from Earth, either. (What happens if the space shuttle's engines go awry? Everyone on board dies, and everyone on the ground speculates as to whether they died within 30 seconds, or survived to hit the ocean.)

The shuttle was an outlier, a rocket without an escape mechanism once the crude, firework-like boosters were lit, which relied on ultra-advanced, brittle and damageable heat shielding for re-entry because it had wings.

The space shuttle was unusual in this regard; Apollo had a launch escape system and IIRC so did its predecessors.

> 1g at 1 atmosphere has disadvantages. Namely: to get off the planet, you will need a fully fuelled multistage rocket with an almost identical profile to rockets you'd launch from ground level on Earth.

Condense Carbon Monoxide and Sulphuric Acid from Venus's atmosphere for use as fuel and oxidizer in a hypersonic rocketplane that tops out at about Mach 11. Have the rocketplane rendezvous with the end of a rotating tether.

http://www.tethers.com/papers/HASTOLAIAAPaper.pdf

No multi-stage rocket. No expendable launch vehicles. That's probably not the actual solution, but it shows that you don't have to have a Falcon 9 equivalent.

> Then you have to fly it out through a hot corrosive acid atmosphere which I don't imagine would be very friendly to machined aluminum.

It should be possible to condense HF out of the Venusian atmosphere, so we should be able to manufacture PTFE locally with input from non-Earth resources. (Mining chondrites from Mercury and Venus-crossing asteroids.)

With a denser atmosphere balloon-based launches become more feasible (on Earth we're already close to the margin where they'd become a good idea).

Why not a space plane? Surely reaching orbital velocity on a platform that is already moving at a decent speed around the planet would ease it somewhat?

For the first problem, we can probably build small "launcher" platforms from lighter gases so it brings the spaceship to an altitude with much less gravity.

The sulfuric acids should be fine with enough protective coating. Earth's atmosphere isn't all that friendly either with rust able metals. Thus we have corrosion-resistant paint.

For the first problem, we can probably build small "launcher" platforms from lighter gases so it brings the spaceship to an altitude with much less gravity.

Uh, no. Sit down with the equations yourself. The main way one counteracts gravity is by gaining orbital velocity. Astronauts aboard the ISS experience almost as much pull from Earth's gravity as you do on the surface. It's that their orbital velocity puts them in a frame of reference that has "microgravity."

When I posit launcher platforms on Venus, the point is to launch from a higher altitude, thus avoid some losses to air friction, and also to use the entire station as reaction mass for launching the payload from an electromagnetic cannon. Doing this avoids the near-exponential nastiness of the rocket equation.

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