Thursday, April 08, 2010

Space Access 2010 - Affordable Spaceflight Beyond LEO by Henry Spencer

Henry Spencer traditionally gives the opening presentation. He started with a couple simple drafts showing the near earth space. He points out that the obvious place to visit first is the moon. Mars is farther away in terms of time, and delta-v. Possible to visit a near earth asteroid. It would take several months. Henry’s said best to go out a month or two, hop on, ride till get closes to earth, and then hop off. A big problem is that the asteroids typically are going fairly fast.

The hardware needed to get to the moon can take us to other places, but going to Mars has additional issues. Get a lot of radiation in going through the Van Allen belt. Good to refuel in Low Earth Orbit.

General Approach: think long haul, focus on transportation services (not programs), plan for multiple destinations. Henry says a focus on Mars is a bad idea, better to be more general. Better to fly more often than to fly with a big spacecraft. Versatility is better than lots of new programs. Henry says NASA likes development, great for an engineer jobs program.

Good to have backup systems. Deep space missions should have more than one ship, so if something goes wrong, have a better chance to survive.

Better to design missions so they don’t have to be self-sufficient. With a general support system then each mission would be cheaper to create. A support system would have things like fuel depots, assembly bases, stopover points, bases and colonies, navigation aids, communication relays, scouts, tugs and so on.

Henry had several suggestions on how to simplify the problem: 1) Pick resonant orbits for first-orbit rendezvous. 2) Tugs for altitude matching. (This means will keep some space hardware in space.) 3) Expendable tether as “upper stage.”

There are several benefits with orbital assembly. If want more, just do a few more launches. Currently the big costs are the development costs. Fuel is relatively free. A simple basic system which takes payload into orbit at an assembly point would be cheaper than developing a large spaceship to be built on earth. There are some issues with building in space, things like thermal controls, power issues, structural stiffening and damping. An assembly base allows you to avoid these issues. Henry said there were some problems with having an assembly base, and gave solutions. He showed a proposal for an assembly base. It looked like a shed with solar arrays. The bottom of the shed was open to the earth. The shed protects the assembly from the heat of the sun and the cold of deep space, and from other stuff in orbit.

He went back to the issue of going to the Moon. There is no good place for an orbital base around the moon. He proposes a ship he calls “The Turtle,” One of them can start the other for the moon.

Henry believes LOX (Liquid Oxygen) is the right fuel for Low Earth Orbit. There are several problems with initially developing LOX on the moon.

Main entry point.

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