Alan Bean, 4th Person to Walk on the Moon, Dies at 86

Re:Alan Bean, 4th Person to Walk on the Moon, Dies at 86 by simonh on Sunday May 27, 2018 @04:04AM (#17165999)

As an exercise, work out how much energy it would take to transport a capsule with three people in it to the moon orbit, send a 2 person capsule to the surface and bring them back. Just raw theoretical energy. Then work out how much actual energy the Apollo program took to build an entire Saturn V rocket and all associated infrastructure. Bear in mind most of the time you’re not just accelerating th capsules, you’re also accelerating the rest of the rocket at various stages. The rocket equation is a harsh mistress. I think you’ll find you are many orders of magnitude off.

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Re:Alan Bean, 4th Person to Walk on the Moon, Dies at 86 by gpm on Sunday May 27, 2018 @09:14AM (#17166764)

There are various ways to cheat the rocket equation that weren't possible during Apollo because of our level of technology, and to some extent the constraints of a mission where a substantial portion of the energy is consumed getting to LEO. I don't want to suggest I know how to build an interplanetary spaceship accelerator, but here are some common basic ideas

- Accelerate the ship be pointing lasers (or something that accelerates matter) at it from the launch point. Now one doesn't need to carry fuel and the rocket equation no longer applies.

- Use some form of ion engine where we accelerate particles to very high speed relative to chemical rockets. This makes the rocket equation very tame since so little of the mass (relatively speaking) is in propellant.

- Combine the above ion engine with some form of "ramjet" that takes hydrogen we collide with and turns it into fuel. This makes the rocket equation irrelevant since we don't carry our fuel (to the extent that we can get our fuel via the ramjet anyways).

Also as laumars says the 0.1% of annual energy usage was just a point of comparison because terwatts is such a foreign unit to most of us (including me) that it doesn't mean anything by itself.

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Re:Alan Bean, 4th Person to Walk on the Moon, Dies at 86 by gus_massa on Sunday May 27, 2018 @04:17PM (#17168901)

You forgot the option of the one-way trip. It's not possible for the Moon, but it may be acceptable for Mars.

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Re:Alan Bean, 4th Person to Walk on the Moon, Dies at 86 by laumars on Sunday May 27, 2018 @05:10AM (#17166148)

The annual energy point is a point of comparison. Obviously we don't have the means of delivering the enegery required yet, and when we do I like to assume many of the issues you raised would also be possible to work around. Such as not requiring as much weight (samples plus autonomous ship and AI means we might not even need to send humans out there in the first shipment).

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