[AR] Orions and PDEs (was Re: More MAX delays.)
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Sun, 26 Jan 2020 17:31:51 -0500 (EST)
On Sun, 26 Jan 2020, John Dom wrote:
Orion is a nuclear PDE concept if I understand it correctly.
Not exactly. Traditional PDEs still have chambers and nozzles, more or
less like conventional engines -- it's just that fuel/oxidizer feed and
combustion alternate, rather than both being continuous.
There are impressive videoclips showing a micro Orion take off using
conventional detonations.
Indeed so, but that was a proof-of-concept demonstrator, and nobody cared
that it used combustion energy and propellant mass very inefficiently,
compared to a conventional rocket.
I thought I never read mentioned *how* existing PDEs are built,
technically, on AR.
Try Bratkovich et al, "An Introduction to Pulse Detonation Rocket
Engines", Joint Propulsion Conference 1997, AIAA 97-2742. There may be
better and/or more recent references -- it's not an area I really follow.
Last I heard, they typically claim a 10-15% advantage in Isp, and
sometimes actually demonstrate that :-), at the cost of (so far) truly
dismal T/W -- very heavy engines with quite low thrusts -- and hideous
noise and vibration. The T/W and the resulting dry mass are bad enough
that *vehicle* performance is rather better if you use a conventional
engine and carry a bit more fuel. Maybe this can eventually be fixed...
maybe. Good luck fixing the noise/vibration problem when shock waves are
an inherent part of engine operation.
As I've mentioned before, I kinda gave up on PDEs when I ran into a paper
explaining how wonderful they were and how they would soon replace all
other kinds of rockets -- in the May 1957 issue of the ARS Journal.
Henry
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