Scram Success

So you've all probably read that the latest Mach10 flight was
successful. The statements from NASA's O'Keefe seem to indicate that
this technology will be used to advance commercial flight, as well as
cheaper access to space.

So in light of these post-Nov16 statements from NASA, will there be a
future for scram?

Some of you have said it's easier to get into space with a rocket, but
some of the news coverage I was reading said scram could at least be
used for a lower-stage booster.

Could scram be suitable for heavy payloads in particular?

(sanman) wrote in news:f144e162.0411161717.6bc4ade8
@posting.google.com:

So you've all probably read that the latest Mach10 flight was
successful. The statements from NASA's O'Keefe seem to indicate that
this technology will be used to advance commercial flight, as well as
cheaper access to space.

So in light of these post-Nov16 statements from NASA, will there be a
future for scram?

Some of you have said it's easier to get into space with a rocket, but
some of the news coverage I was reading said scram could at least be
used for a lower-stage booster.

Could scram be suitable for heavy payloads in particular?


Not at all, I think. Lots simpler to use conventional rockets; scaling
a scramjet for heavy payloads is way off into the future, if it all.
There's a basic problem of just getting the vehicle up to a speed
where the engine will work at all, airframe heating/cooling, and
actually realizing the weight savings when the complex airframe eats
up the weight budget that came from the supposed oxidizer savings.

Looks nice on paper, but the practical reality has a long way to go.

Some sort of air-augmented combined cycle rocket engine might have
some possibilities (think of a rocket engine firing into a ramjet
duct, with a variable fuel/oxidizer ratio).

But when you look at the complexities involved, the basic simple
rocket still makes a lot more sense. And it's off-the-shelf.

--Damon

sanman wrote:

So in light of these post-Nov16 statements from NASA, will there be a
future for scram?

Yes, but not for launchers.

Paul

On 16 Nov 2004 17:17:02 -0800, (sanman) wrote:

So you've all probably read that the latest Mach10 flight was
successful. The statements from NASA's O'Keefe seem to indicate that
this technology will be used to advance commercial flight, as well as
cheaper access to space.

Don't scramjets need to be started at upwards of Mach 4? If you
already have an airliner that can do Mach 4 (an enormous technological
leap, by the way), why bother with the scramjet?

Brian

In article ,
sanman wrote:
So you've all probably read that the latest Mach10 flight was
successful. The statements from NASA's O'Keefe seem to indicate that
this technology will be used to advance commercial flight, as well as
cheaper access to space.

Those are standard fantasies, but both fairly unlikely.

Commercial flight simply does not see substantial payoffs between about
Mach 5 and near-orbital speeds. Mach 5 cruise gets you anywhere on the
planet in four hours, assuming a direct route. Beyond that, incremental
benefits fall off sharply as preflight/takeoff/landing/postflight time
overheads swamp the further time savings, and costs rise sharply as the
aircraft and their maintenance get more expensive, new fuel infrastructure
becomes necessary, and traffic-control problems multiply.

And the idea that it makes sense for launchers to trade simple, cheap,
lightweight, well-understood LOX tanks for complex, technically
problematic, heavy, and poorly developed scramjets is utterly ludicrous.
It would be difficult to find a *stupider* design change.

So in light of these post-Nov16 statements from NASA, will there be a
future for scram?

For military applications, perhaps. They're the only real customers.
Hint: the detailed design of the X-43 scramjet is classified.

Some of you have said it's easier to get into space with a rocket, but
some of the news coverage I was reading said scram could at least be
used for a lower-stage booster.

If somebody else builds a large scramjet aircraft for some other purpose,
using it to carry an air-launched rocket up to speed and altitude would be
interesting. There's no way that *developing* it could possibly be
justified as part of a launcher project.

Could scram be suitable for heavy payloads in particular?

Contrariwise: almost any air-launch scheme will have quite limited
payload because of the limitations of the launch aircraft. For getting
big payloads into orbit, brute force using rockets is far superior: they
scale much better.
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |

On Tue, 16 Nov 2004 19:32:48 -0600, Damon Hill
wrote:

Some sort of air-augmented combined cycle rocket engine might have
some possibilities (think of a rocket engine firing into a ramjet
duct, with a variable fuel/oxidizer ratio).

But when you look at the complexities involved, the basic simple
rocket still makes a lot more sense. And it's off-the-shelf.

--Damon

Yeah. Went though all of this in scrapping scram.
I have noted many people seem doubtful if much is saved by
using the oxygen in the atmosphere.
My stand was to wait for more solid experimental data as I find
that theoretical models often miss crucial points.
Remember that 15 years ago bumble bees couldn't fly in our aerodynamic
models.
It has been pointed out that a rocket needs to accelerate continuously
and that a scram-jet for atmosphere usage only need to maintain
constant speed and that these are different problems.
As I said I need a optimal scamjet tranjectory and a optimal
rocket tranjectory to get the numbers.
I would also want to allow for advances in both scram-jets
and rockets. Remember that another exciting NASA project
is testing out a revolutionary Russian rocket engine developed
for the scrapped Russian moon program. As far as I understood
(no I am not a rocket scientist) used a turbine to power the fuel
pumps and feed it into the thrust of the engine developing 20-30% more
thrust for the same amount of fuel.
Exciting times!
I am a bit disappointed that we have not yet seen a successful
single stage to orbit rocket this decade.
But I am hopeful that we will see one in the next.
We are so close..

--
Using M2, Opera's revolutionary e-mail client: http://www.opera.com/m2/

On Wed, 17 Nov 2004 16:30:21 GMT, Rand Simberg
wrote:

On Wed, 17 Nov 2004 14:26:52 +0100, in a place far, far away, "John
Thingstad" made the phosphor on my monitor
glow in such a way as to indicate that:

I am a bit disappointed that we have not yet seen a successful
single stage to orbit rocket this decade.
But I am hopeful that we will see one in the next.
We are so close..

Actually, it's not clear that we're close at all. Fortunately, SSTO
is not necessary to make access to space affordable.

Well you probably know more about this than I do.
Perhaps I am a bit over optimistic.
Still it would be great..

--
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On Wed, 17 Nov 2004 16:30:21 GMT, Rand Simberg
wrote:

On Wed, 17 Nov 2004 14:26:52 +0100, in a place far, far away, "John
Thingstad" made the phosphor on my monitor
glow in such a way as to indicate that:

I am a bit disappointed that we have not yet seen a successful
single stage to orbit rocket this decade.
But I am hopeful that we will see one in the next.
We are so close..

Actually, it's not clear that we're close at all. Fortunately, SSTO
is not necessary to make access to space affordable.

I looked over the web site at Venture Star, but I never figured out
why the program was scrapped.
Were there fundemental problems or just that they lagged behind scedule?

--
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On Wed, 17 Nov 2004 17:11:41 GMT, Rand Simberg
wrote:

On Wed, 17 Nov 2004 14:37:36 +0100, in a place far, far away, "John
Thingstad" made the phosphor on my monitor
glow in such a way as to indicate that:

Actually, it's not clear that we're close at all. Fortunately, SSTO
is not necessary to make access to space affordable.

I looked over the web site at Venture Star, but I never figured out
why the program was scrapped.

I'm sure that that site would be quite uninformative. The answer is
too embarrassing to put it in an official site.

Were there fundemental problems or just that they lagged behind scedule?

There were fundamental problems, too numerous to mention right now,
but suffice it to say that they attempted to combine too many risky
and unnecessary technologies in a single test vehicle. It was a
tremendous boondoggle, but NASA didn't figure that out until they'd
wasted a billion dollars of taxpayer money on it.

The program was based on a false premises. Building the X-33 was
neither a necessary, or sufficient condition to building an SSTO, and
SSTO is neither necessary or sufficient to getting cheap launch.

yeah.. Put that way I can see what you mean.
I have said before that the focus should be on cutting pre launch
checks and assembly. Even if it requires more fuel perhaps giving
the specs a bit of leniency so you don't need to check every not
and cranny might pay off.


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In article ,
John Thingstad wrote:
Remember that 15 years ago bumble bees couldn't fly in our aerodynamic
models.

No, that's an old myth. The analysis that said the bumblebee couldn't fly
started by assuming that it was a fixed-wing aircraft, and the whole point
was to demonstrate that fixed and moving wings follow different rules.

As I said I need a optimal scamjet [trajectory]...

Once again, the Goddess of Fortuitous Typos strikes!

...Remember that another exciting NASA project
is testing out a revolutionary Russian rocket engine developed
for the scrapped Russian moon program.

That's a bit muddled... The NK-33, developed for the Russian lunar
program, was tested by Aerojet. The one on the NASA test stands was the
RD-180, which is a new engine -- derived from the RD-170 developed for the
Zenit launcher -- and is not related to the old lunar program.

As far as I understood... used a turbine to power the fuel
pumps and feed it into the thrust of the engine developing 20-30% more
thrust for the same amount of fuel.

Same principle used by the SSME, developed in the US in the 1970s. Mind
you, the Russians did have some interesting variations on the idea, and
they were first -- they'd been doing it since the early 1960s -- but
"revolutionary" it's not.

I am a bit disappointed that we have not yet seen a successful
single stage to orbit rocket this decade.

Me too. But as Rand notes, a successful *cheap* launcher is the important
thing -- how many stages it has is a secondary issue, and there are some
differences of opinion :-) about the best number.
--
"Think outside the box -- the box isn't our friend." | Henry Spencer
-- George Herbert |