Pulse Detonation Engines

The recent issue of AviationWeek features Pulse Detonation Engines,
including one being showcased at Oshkosh by the Air Force Research
Labs:

http://www.pr.afrl.af.mil/divisions/prt/pde/index.html

Cool info, pics and videos on the AFRL site.

Hmm, that they're using a LongEZ is to me rather reminiscent of XCOR
using it as a testbed for their alcohol-powered rocket engine. It's
also impressive that they were even able to get a test demonstrator
model to work using just off-the-shelf auto parts.

(sanman) wrote in message . com...
The recent issue of AviationWeek features Pulse Detonation Engines,
including one being showcased at Oshkosh by the Air Force Research
Labs:

http://www.pr.afrl.af.mil/divisions/prt/pde/index.html

Cool info, pics and videos on the AFRL site.

Hmm, that they're using a LongEZ is to me rather reminiscent of XCOR
using it as a testbed for their alcohol-powered rocket engine. It's
also impressive that they were even able to get a test demonstrator
model to work using just off-the-shelf auto parts.

I'm doubt PDE will help much for rocket tech. Quite simply the fact
that it is *not* a constant thrust device means that everything needs
to be heaver than a constant pressure rocket enegine equiviliant (ok
you save on turbopumps). Also the fact that you have a shockwave
futher complicates the peek stresses involved.

Greg

(Greg) wrote in message m...
I'm doubt PDE will help much for rocket tech. Quite simply the fact
that it is *not* a constant thrust device means that everything needs
to be heaver than a constant pressure rocket enegine equiviliant (ok
you save on turbopumps). Also the fact that you have a shockwave
futher complicates the peek stresses involved.

Well, consider that the device is a simpler and more rugged design
with fewer moving parts, and despite the cyclical stress spikes, its
efficient combustion offsets that. With recent advancements in
materials strength, stronger may not always mean heavier.

The idea of pulsed thrust also seems more suited towards dealing with
the full range of dynamic/turbulent stresses of atmospheric flight, as
opposed to constant thrust which is merely idealized towards fighting
the constancy of gravity. I'd wonder if some kind of hybridized engine
might not be possible, perhaps in a DC-X type of configuration.

(sanman) wrote in message . com...
(Greg) wrote in message m...
I'm doubt PDE will help much for rocket tech. Quite simply the fact
that it is *not* a constant thrust device means that everything needs
to be heaver than a constant pressure rocket enegine equiviliant (ok
you save on turbopumps). Also the fact that you have a shockwave
futher complicates the peek stresses involved.

Well, consider that the device is a simpler and more rugged design
with fewer moving parts, and despite the cyclical stress spikes, its
efficient combustion offsets that. With recent advancements in
materials strength, stronger may not always mean heavier.

Rugged design is a feture of just that, the design. Rocket engines
could be very rugged, with reliable turbo pumps and all, it just
requires proper saftey margins etc. As Jet engines are very
reliable... Also PDE's will probably end up with just as many moving
parts as a pump fed engine due to very fast timing requierments.

Also can you have an effecent nozzel with a PDE?.. last i read the
answer was no. So efficient combustion counts for zero.

And for any givin material *stronger* means thicker means *heaver*....

The idea of pulsed thrust also seems more suited towards dealing with
the full range of dynamic/turbulent stresses of atmospheric flight, as
opposed to constant thrust which is merely idealized towards fighting
the constancy of gravity.

Pulse thurst means *bad* vibrations. Usally on the order of
100Hz..What are you on about?

Remember Rocket engines are already very good at what thay do. Its
hard to beat.

Greg

I'm doubt PDE will help much for rocket tech.
And I very much doubt that three little sailing ships can discover a new
world across the ocean.
Pessimists talk that way because they think it makes them sound smart.
^
//^\\
~~~ near space elevator ~~~~
~~~members.aol.com/beanstalkr/~~~

"Allen Meece" wrote in message
...
I'm doubt PDE will help much for rocket tech.
And I very much doubt that three little sailing ships can discover a
new
world across the ocean.
Pessimists talk that way because they think it makes them sound smart.
^
//^\\
~~~ near space elevator ~~~~
~~~members.aol.com/beanstalkr/~~~

Perhaps ... SOME pessimists talk that way because they they know quite a
bit more than you do.

Really, just how many PDE's have been flown in the past 50 years?

How many have boosted a payload to supersonic speeds let alone hypersonic
speed?

How many funded projects are there researching PDE's and their application
working toward a flying prototype?

If the answers to those questions are zero or some close approximation,
it's not hard to see why doubt is the best approach today. Flippant
remarks such as your 'Pessimists ...' remark only sound smart in
hindsight. It is easy to forget all the crack pot ideas that failed for
every one that succeeds.

Allen Meece wrote:

I'm doubt PDE will help much for rocket tech.

And I very much doubt that three little sailing ships can discover a new
world across the ocean.
Pessimists talk that way because they think it makes them sound smart.


Or perhaps they know something that you don't?

BTW, Columbus wasn't *looking* for a new world, but another route to
*known* locations. Earth was spherical, but larger than he believed. The
continents of North and South America were unknown to him, and had they
not existed, his ships would not have made it to Asia. Rather like
trying to reach Mars with an unmodified Apollo.


--

You know what to remove, to reply....

How many funded projects are there researching PDE's and their application
working toward a flying prototype?

AFRL in Dayton has a PDE that works and they are putting it in the good old
Long EZ aircraft to test, same as Xcor did. Their website says they'll fly
it... last autumn 8-] Well, soon.

If the answers to those questions are zero or some close approximation,
it's not hard to see why doubt is the best approach today.
Doubt is a self fulfilling sentiment so I do without it and see what destiny
holds.
^
//^\\
~~~ near space elevator ~~~~
~~~members.aol.com/beanstalkr/~~~

Joann Evans wrote in message ...
Or perhaps they know something that you don't?

BTW, Columbus wasn't *looking* for a new world, but another route to
*known* locations. Earth was spherical, but larger than he believed. The
continents of North and South America were unknown to him, and had they
not existed, his ships would not have made it to Asia. Rather like
trying to reach Mars with an unmodified Apollo.

I'll add a nit here that Columbus did have some information
that there were populated land masses not too far to the
West across the Atlantic. He took this for confirmation
that Asia / Japan was not far off, though it actually
indicated something else entirely.