Sunday, December 16, 2012

Getting rocket fuel into orbital space depots

Speculation alert
MAB post 11


John Powell of JP Aerospace wants to get up to orbit with an airship.  John Hunter wants to use an air gun to get fuel up to orbit.  Now, this may be a crazy concept, but here goes.  Combine the two by sending 100 lb payloads to orbit from JP Aerospace's Dark Sky Station.

Hunter says he can do 10 shots per day.  That would be a 1000 lbs per day.  After a month, you have a respectable amount of fuel in orbit.

Another purpose for using the Dark Sky Station this way is to avoid the energy loss of going through the lower atmosphere at high velocity.  This enables a smaller gun to do a bigger job.

As I noted earlier, you can't put a gas gun on a plane.  You can't even put a gas gun on an Ascender.  But you can assemble one in a Dark Sky Station because the Station is frickin' huge.

Getting the gun there is only half the problem, though.  Maybe the easier half.  The other half is what to do about the recoil of the gas gun?  It will be too much for the Dark Sky Station to handle.

One thing that could be considered is to capture the energy of the recoil and use it to make work.  That work will act as the buffer that will soften the recoil of the gas gun.

How to do that? The old 64K dollar question.

You could use the energy to spin up one or more flywheels.  A flywheel with enough mass and capability to spin at great velocity.

Update:

As long as this is a speculative post, let's use the MAB concept in concert with this concept.  The MAB would take it to orbit.  The Hunter gas gun would give it a boost to 1/2 orbital velocity.  The total wet mass calculated assuming 20% payload fraction ( Parkins assumption) gives us a vehicle of under 1k lbs.


Wet mass for 100 lb payload launched from DSS/MAB assuming 20% mass fraction (MAB module)

What to do about that recoil?  Use the Airship to Orbit module launched from the Dark Sky Station for your launch pad.  Point it in the direction so that the recoil forces the Airship down.  The buoyancy of the Airship will force it to come back up.  You could also dampen the recoil a bit as described above.

The gas gun would have a smaller payload than what Hunter is talking about.  But the extra mass brings it back up to full size.  That's much too big again.  So, we pare down the size of the gas gun by making it less ambitious.  It will only go 1/2 orbital velocity.  A conventional rocket will take it to orbital velocity from there.

Still worried about the recoil.


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