Wednesday, February 2, 2011

The Hindenberg

I was thinking about this early today with respect to the method in which JP Aerospace wants to get to orbit. The Hindenberg was a huge airship, over 800 feet long.  That's what I was thinking about.  JP's idea of using large "V" shaped airships will be even bigger than this.  I think he wants to use 900 foot long airships.

As with the Hindenberg, these should carry a lot of freight.  But these won't be the airships that get to space. The ones that will go will be the real monsters.  Over a mile long.  But these will never land on the ground. They will dock to a permanent Dark Sky Station (DSS) which will float at 170k feet in the sky.  The Airship to Orbit, or ATO, will depart from the DSS and return there after completing a mission.

JP's airships will use hydrogen, just as with the Hindenberg.  Should there be concern about this?  The cause of the Hindenberg disaster has not been completely resolved.  I have heard that the hydrogen lifting gas was not the culprit, though.

Control of airships may be dicey, especially at take off and landing.  Would it be better to have some sort of protected area that gives shelter from wind?  Launching and landing in a big Meteor Crater is way of avoiding wind.  It is always calm at the bottom of the crater.

Maneuvering the airships is also tricky.  I do not think it has any control surfaces as does a plane.  It moves the air inside the ship around in order to facilitate movement.  One thing I wondered is if it is feasible to have the ATO do an orbit around the DSS.  If the orbit is really large, say 200 miles from the DSS, it could stay within range of an energy source that can be beamed to it.  That would come in handy in attempting to get to orbit.  At least you wouldn't have to devote mass for lots of solar panels to power the thing to orbit.

The ATO could do a corkscrew type ascent while orbiting the DSS.  Once it gets high enough, the rest of the trip to orbit could be a more standard rocket trajectory.  The difference is that the launch point is much higher. Right on the edge of space, as a matter of fact.  It is a this point that aerodynamic lift is lost, but drag could still be a problem.

It is not so much mass that is a concern, but its sheer size that could be a hindrance in getting to space.  Such a large craft can generate a lot of friction at high velocities.   I would hypothesize that you may want to shrink the size of the craft to a much smaller size once you stop getting aerodynamic lift and air drag becomes a problem.  Solar panels can get in the way.  But a small, compact, heat exchanger could transfer the energy provided from the DSS into thrust to move the craft into an upward trajectory, similar to the one proposed by Parkin in his doctoral thesis.  Parkin's concept avoids the hardest acceleration while in the lower atmosphere.
That concept may be feasible in this context as well.

Another idea that I got, which would eliminate some mass, would be to use the surrounding atmosphere as reaction mass.  The air would be drawn into the heat exchanger, then the heated air would be expelled out, giving thrust.  Proceeding in this manner would eliminate the need to carry reaction mass for part of the trip to space.  This would be useful at lower altitudes.  At some point, you would have to rely upon on board reaction mass.

But in the end, how big can the craft get before it becomes unmanageable?  JP has two major issues to solve. Size is relevant to the issues of air drag and energy.  You need a way to get energy to the airship, but solar energy takes up a lot of surface area which may cause a problem with air drag at higher velocities.  The beamed propulsion concept may help solve both problems.  You can keep the solar panels to a minimum and still have an energy source which can get you to orbit.

Update 3:45 cst

I thought it may be useful to see some illustrations of JP Aerospace's concept.    Here is the first stage of his 3 stage concept.  It takes off from Earth and goes to the Dark Sky Station

Source: Floating to Space DVD
 After it takes off, it rendezvous with the Dark Sky Station (the airship is circled) look how big the DSS, the ATO is on the left.  Keep in mind each side of the "V" is over 1 mile long.

Source: Floating to Space DVD
 And finally the ATO in orbit:

Source: Floating to Space DVD

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