Re: Brit Scramjet Model Does Mach-8 - New Era of Cheap Sat Launches Near
- From: Scotius <wolvzbro@xxxxxxxx>
- Date: Tue, 28 Mar 2006 14:53:53 -0800
On Tue, 28 Mar 2006 13:40:55 GMT, bw@xxxxxxxxxx (B1ackwater) wrote:
(foxnews)
LONDON ? British scientists completed a test flight Saturday of a jet
engine that could eventually turn long-haul flights to Australia or
Japan into two-hour hops.
The Hyshot craft reached speeds of 6,000 mph ? Mach 8, or eight times
the speed of sound ? over the outback in South Australia.
The craft, which was just 4 feet 6 inches long, was testing a
revolutionary scramjet engine designed by Qinetiq, formerly the
British government's defense research agency.
Scientists believe that the scramjet could one day be used to power
super-fast intercontinental passenger planes.
They've been making those predictions since the '70s. Either
Popular Mechanics or Mechanix Illustrated ran an article back in the
'70s called "The Flying Stovepipe". It was explained that a scramjet
is like a ramjet, except that the combustion of the fuel and air
mixture takes place at supersonic speed (thus the name "SCRamjet",
standing for "Supersonic Combustion Ramjet"). They also explained that
keeping the mixture burning is like keeping a match lit while driving
at high speed in a convertible.
"Ultimately, we hope to be able to use it to launch satellites into
low-Earth orbit," said Professor Allan Paull, of the University of
Queensland's center for hypersonics, which is working with Qinetiq.
It's great for travel up to as high as the engine can breathe
air. After that they have to use pure rockets. Alan Bond of Great
Britain designed a Scramjet vehicle that used engines he called
"SABRES" (Synergistic Air-Breathing Rocket Engines). They would use
air for Scramjet operation while able to, and neatly transition to
pure rocket when the atmosphere got too thin to feed the jets. It's a
nice idea, but they've been working on these for decades already, and
I'm not sure it's going to come to fruition anytime soon.
The scramjet ? the name comes from Supersonic Combustion RAMjet ? is
among the simplest of all engines because it has no moving parts.
It works by taking in air, mixing it with hydrogen and simultaneously
compressing it, generating extremely high temperatures which ignite
the mixture to create a surge of jet propulsion. The only by-product
is water.
That's true, and it generally works better in a ramjet because
at Scramjet speeds, the incoming air is very hot, and therefore
already expanded. What they really want to be able to do is take in
air without it getting so hot and therefore not being to take in as
much as they need for efficient operation. Don't forget efficiency.
The big advantage of such craft is that they would not need to carry
tanks loaded with a source of oxygen as well as fuel, meaning they
would have much more space for payload.
A plane that has a Scramjet that can also be used as a rocket
is potentially more efficient than a pure rocket, due to the air
breathing aspect, but don't forget that Scramjets are more complicated
than rockets, and therefore heavier. They keep talking about it, but
if they haven't done it in more than three decades, there has to be a
reason. Russia is a little farther along in Scramjet development than
the other countries still working on them.
However, there are many obstacles to making scramjets.
Perhaps the biggest is that they start working only at five times the
speed of sound. Below this speed, the mixture of hydrogen and air
would not be sufficiently compressed to ignite.
This means that scramjet-powered craft must first be accelerated by
another means, such as a rocket-powered first stage.
. . . . .
Um ... I'll pass on flying in a rocket-boosted hydrogen-powered
passenger plane if you don't mind ........
However, as a platform for satellite launches, scramjet aircraft
clearly have considerable potential. Might even be useful for
getting a small manned orbital vehicle most of the way into
space - thus allowing the use of rather small rockets for the
final climb. This would knock a big chunk off the price of
orbiting people (and moderate cargoes).
Very small satellites are already launched by dropping a rocket
from modified B-52s. Getting 50,000 feet of the atmosphere out
of the way is a BIG help. Scramjet-powered vehicles, probably
automated, could get much more of the atmosphere out of the
way PLUS get the rocket up to about a third of the necessary
orbital speed much more efficiently and economically than
using a huge booster stage in a ground launch. And, unlike
shuttles, the scramjet platform would REALLY be reusable,
capable of a flight or two every DAY.
Once they can get to mach 10 then they're ready to build a
full-scale model.
Price-per-pound has always been the bugaboo limiting our use
of space technology. It hasn't really changed since the 1960s.
Cut that price in half, or by an order of magnitude, and vast
new frontiers will open up. TWO orders of magnitude however,
what's really necessary for all 'round commercial and private
exploitation, will remain out of reach. Have to wait for
'warp drive' or something ...
.
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