I think the real problems in getting this to work are base station power, targeting the beam accurately enough in later stages of launch and keeping the heat exchanger from point burn through in the case of uneven fuel flow. I also see shooting a beam of microwaves through a cloud of superheated steam being a problem when they switch from helium to hydrogen - steam is much more absorptive of microwaves than is regular mix air and the hydrogen plasma is going to combine with oxygen in the atmosphere in it's entropic journey back to equilibrium..

Dave
Your 'reality', sir, is lies and balderdash,
and I'm delighted to say that I have no
grasp of it whatsoever.
- Baron Munchausen

On Thu, Jul 23, 2015 at 5:34 PM, Ethan McKinney <ethan.mckinney@gmail.com> wrote:

Yeah, safety.
On Thu, Jul 23, 2015 at 5:29 PM, Richard Aiken <raikenclw@gmail.com> wrote:
On Thu, Jul 23, 2015 at 8:22 PM, Richard Aiken <raikenclw@gmail.com> wrote:
On Thu, Jul 23, 2015 at 8:14 PM, Richard Aiken <raikenclw@gmail.com> wrote:
This article says hydrogen fuel provides thrust after passage through an exchanger heated by the externally-generated microwaves. The result craft would simply "glide back to the launch pad, refuel, and will be ready for its next flight."

And googling further . . .

Wikipedia says that such a microwave powered exchanger was proposed as a concept in 2001.

So maybe the "breakthrough" is that they've actually made it work? At least in the lab?

Although . . . one has to wonder why they used helium in the tests rather than hydrogen, if the later is the fuel they're aiming at actually using for a craft.

Safety concerns, perhaps? Hydrogen being a tad explosive and all?

--
Richard Aiken

"Never insult anyone by accident." Robert A. Heinlein
"A word to the wise ain't necessary -- it's the stupid ones that need the advice." - Bill Cosby
"We know a little about a lot of things; just enough to make us dangerous." Dean Winchester
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