Parkin's Microthermal Rocket revisited

Having finished with the Augustine Commission posts, let's move on to Parkin's device.


This post is based upon the pdf file referenced in the previous post above.  Who is Kevin Parkin?  Nextbigfuture blog has a post which says a bit about who he is and his device.

One of the major advantages of a beamed microwave external propulsion system, said Kevin Parkin, the deputy director of the Mission Design Center at NASA's Ames Research Center in Mountain View, Calif., is that it can bypass some of the typical constraints of a traditional propulsion engine.

There is a Cnet story from the post above which tells more ... 

But NASA is already looking into the technology, Parkin said, pointing to a research project under way at the U.S. space agency's Glenn Research Center in Cleveland.

 It appears that the Microwave Thermal Propulsion concept evolved out of work on Laser Propulsion.
From Parkin's thesis:

The use of lasers for propulsion was first suggested by Kantrowitz (1972) and independently by Minovich (1972) a short time later. Kantrowitz focused on lasers in his seminal paper because high power microwave sources at wavelengths practical for beamed- energy launch did not exist at that time (Kantrowitz, 2004).

 Also:

...Most of the attention thus far has focused on ablative laser propulsion (Pakhomov and Gregory, 2000). 

The laser lightcraft (Wang et al., 2002) has a diameter of 12.2 cm and weighs roughly 50 grams. It is powered by a 10 kW CO2 laser. A parabolic mirror on the underside of the craft, shown in Fig. 1-14, focuses the beam into the engine air or propellant. The pulsed laser heats the air, causing it to break down into a plasma. The plasma strongly absorbs the incoming pulse, heating to roughly 18,000 K before exploding from the annular  underside region, generating thrust.

 And:

The ablative microwave lightcraft concept of Myrabo and Benford (1994) shown in Fig.1-15 uses microwaves rather than lasers. The concept is airbreathing but switches to an on-board hydrogen supply for the later stages of ascent (in vacuum).  

It was a short step from there by building on the work of the nuclear thermal concept which was almost brought to prototype during the Apollo era. 


Why use Microwave Thermal Propulsion?  From the thesis:

This thesis sets forth the new approach of microwave thermal propulsion, which belongs to the wider class of heat exchanger-based propulsion techniques that includes nuclear thermal and laser thermal propulsion. 

Also:

The past 40 years of launch prices (Fig. 1-1) suggest that the elasticity of demand is locally flat at the present launch price of $10,000 per kilogram of payload, in essence a metastable level, and that an evolutionary path to a lower launch price does not exist.

And:

This thesis offers a technological solution to the problem above: The Launch Problem.  ...

The combined effect of lower structural cost, greater payload fraction and higher flight rate can profoundly alter the economics of launch, minimizing the need to boost launch demand in order to solve the launch problem.

According to the Nextbigfuture blog post above, the device may go to prototype by 2018.