Monday, January 31, 2011

Combinations, Part 2

I first wrote about Parkin's microwave thruster here.  To recap briefly, it uses microwave energy to heat the reaction mass which provides thrust to send the rocket into orbit.  It differs from chemical rockets in that it doesn't use combustion to achieve thrust.  The necessary energy will come from a base station on the ground and this will provide the energy to get to orbit.

My proposed combination follows:   But what if you could place the base station in one of JP Aerospaces' proposed Dark Sky Stations?  It would provide energy to lift the airship nearly vertical until it is out of the atmosphere.  Then, without the friction caused by the massive size of the airship, it could then fire an onboard rocket and achieve orbital speed before it re enters the atmosphere.

In practice, the Airship To Orbit (ATO) vehicle will leave the Dark Sky Station (DSS) as currently envisioned.  But it would have to stay within reach of the energy source of the DSS in order for this to work.

Once it reaches it's limit of acceleration and altitude, the DSS then fires its beam and this will give thrust to the ATO causing it to rise nearly vertically.  This is the trajectory proposed by Parkin and for the same reason.  But Parkin wants out of the atmosphere because he wants to impart massive forward acceleration in order to get to orbital velocity within 200 miles of the range of the microwave source.  But to avoid massive g forces in that trajectory, just raise the airship even higher in order to get potential energy that can be translated into forward speed to orbit.  While falling back to earth, apply rocket power to counter the gravity of the earth and using that energy in the fall combined with the onboard rocket's energy will hopefully impart sufficient energy to get to orbit.

Parkin proposed a range of 200 miles for his microwave energy source.  If you could add that much altitude to the ATO, it would have the 200 miles plus the 30 miles or so of the DSS giving a final altitude of 230 or so miles before it started falling back.  If possible, forward thrust could also be supplied as in the Parkin model trajectory, but without the significant g forces.  The goal is to use this for manned launches.  Parkins model trajectory has too much g forces for humans to be onboard.  This proposition would use the same conceptual trajectory, but in a novel way in order to achieve orbital velocities without excessive g forces.

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