...Mars Rover in Trouble? Or a hoax video?

wrote in message
ups.com...
On Jul 8, 6:23?pm, "George Dishman" wrote:
"Robert Maas, seehttp://tinyurl.com/uh3t" wrote in
...

From: "George Dishman"
a large part of the cost is the ground operations after they
land. The DSN in particular is a very limited resource.

I agree. But I see a solution to make everyone happy: Launch more
missions than DSN can fully support.

We are already there, last I heard there were about
20 hours of requests for every hour available. So
if even one is successful, what other missions would
you switch off?

But I agree, we could really really use more DSN capacity, both for
raw throughput, and redundancy in case of local disaster (wildfire,
earthquake, tropical storm, etc. etc.). But until we have more, we
needn't artificially limit the number of simultaneous deep space
missions for fear of not having enough DSN capacity.

There's no point launching missions if we can never
point a receiver at them. I believe there are plans
afoot to increase capacity but whether that exceeds
the planned data return rate of future missions is
another matter. Bear in mind modern probes tend to
generate a lot more data than those of a decade ago.

Certainly more capacity for the DSN would be good, but
more probes before the capacity is there makes little
sense to me. YMMV of course.

George

theres more than one way to get data back.

how about a few orbiting comm repeater satellites?

Mars orbiter already does that, unless you meant
putting the Earth segment into space. That makes
no sense, it would just increase the cost. Remember
you are talking of 70m dishes weighing hundreds of
tonnes with positions that need to be known to a
few cm at all times.

in orbit they pick up the low power transmissions boost and transmit
back?

More importantly, it picks up data at high rate
locally for the short periods the lander is in
view and stores it until it can be sent to Earth
when the DSN is available.

think out of the box the box isnt your friend

They are way ahead of you. You can learn lots he

http://deepspace.jpl.nasa.gov/dsndocs/810-005/

;-)

George

On Tue, 10 Jul 2007 14:28:39 GMT, h (Rand
Simberg) wrote:

On Mon, 09 Jul 2007 21:12:07 -0600, in a place far, far away, Scott
Ferrin made the phosphor on my monitor glow in
such a way as to indicate that:


and thank god they're not trying something like the "flying crane" to drop
off the next lander!


Oh yeah, don't forget about doing anything like flying a fully
integrated scramjet engine with airframe to mach 10, either (X-43
anybody?). ;-)
-Mike


You might want to look a little closer at scramjet progress.

There is no scramjet progress that's going to have an effect on space
transportation any time soon. The best scramjet possible will still
have inferior performance to a rocket.


Never said there was. My point was scramjet progress was derailed for
decades simply because of lack of interest. Progress isn't nearly as
far along as it should be. I blame it one the near-sighted
man-in-a-can method of getting into space.

Scott Ferrin wrote:

My point was scramjet progress was derailed for
decades simply because of lack of interest.

Ummm... it might just possibly also have something to do with

(1) the limits of CFD -- already dicey around a scramjet inlet, and
worse in the combustion zone
(2) the need for a rocket launch before you can even fire up your
prototype. There are Mach 10+ wind tunnels, but they're small and
limited to extremely brief "shots." Kinda slows down the
test-modify-test cycle...

In article ,
Scott Ferrin wrote:
...My point was scramjet progress was derailed for
decades simply because of lack of interest.

Hardly. Scamjets, er excuse me I meant scramjets, have gotten a bundle
of money in the last 30-40 years -- rather more than has been spent on
improvement of *rocket* propulsion technology in the same timeframe. If
there's been a lack of progress, it's because the technology has so many
problems, not because it's being neglected.
--
spsystems.net is temporarily off the air; | Henry Spencer
mail to henry at zoo.utoronto.ca instead. |

Henry Spencer wrote:

In article ,
Scott Ferrin wrote:
...My point was scramjet progress was derailed for
decades simply because of lack of interest.

Hardly. Scamjets, er excuse me I meant scramjets, have gotten a bundle
of money in the last 30-40 years -- rather more than has been spent on
improvement of *rocket* propulsion technology in the same timeframe. If
there's been a lack of progress, it's because the technology has so many
problems, not because it's being neglected.

It's not been neglected, if your developing a weapon. Which is problem with
most research and development in this area. Weapons fly fast and low in the
atmosphere, and it's an endurance problem. Their purpose is destruction,
and their target is on Earth, which is about as low in the atmosphere as
you can get. An acceleration type mission profile is different, has
different requirements and different constraints. This hasn't been done.
Adding LOX to the flow, most definitely is very anti-endurance, and
pro-acceleration.

Scramjets haven't had Fluid Variable Intakes attached to them yet. As the
speed of a Ramjet increase, so does the compression (area) ratio of the
Inlet. This can be done with Fluid instead of an all variable structure
solution. At the point of instability at the throat, where the air begins
to disassociate, the Fluid is turned off. The normal shockwave at the inlet
throat travels through the engine and out the nozzle, it's now operating as
a Scramjet. All done with the twist of a valve, instead of complex variable
structures. Now as the Scramjet's velocity increase, so does the LOX flow
in the Intake, keeping the operating conditions (Mach Number) constant, or
within the design Mach Number range.

Film wall cooling can also be done with Fluid Variable Intakes, just like a
rocket engine nozzle operating in reverse. What fun it is to play with
Fluid Variable Intakes. Fluid Variable Intakes can be used with Turbojets
to operate above what is considered their normal upper Mach limit, Ramjets
to operate above their normal upper Mach limit and Scramjets above their
normal upper Mach limit. Fluid Variable Intakes simplify and smooth the
transitions from one to the next and ...

We haven't even started discussing hypersonic (or is that ultra-hypersonic)
engines (the next step after Scramjets) and how they work. Which is
probably important in understanding Scramjets.

--
Craig Fink
Courtesy E-Mail Welcome @

Craig Fink wrote:

Scramjets haven't had Fluid Variable Intakes attached to them yet. As the
speed of a Ramjet increase, so does the compression (area) ratio of the
Inlet. This can be done with Fluid instead of an all variable structure
solution. At the point of instability at the throat, where the air begins
to disassociate, the Fluid is turned off. The normal shockwave at the inlet
throat travels through the engine and out the nozzle, it's now operating as
a Scramjet. All done with the twist of a valve, instead of complex variable
structures.

You seem to have an exaggerated idea of our mastery of high-energy
fluid dynamics. It has always been *hard* stuff, and for all the
progress in computational FD it remains so. There is a reason why
physicists have been calling turbulence "the work of the Devil" for
150 years; it's where what we now call chaos first forced itself on
their attention, because very small irregularities tend to get big
very fast. There is a reason why predicting hurricane behavior is
tricky, why killing off combustion instability in rocket engines is
still half a black art, why tokamaks keep turning up fascinating new
ways for plasma to kink itself, etc, etc, etc.

It *sounds* cool as can be to shape supersonic-hypersonic inlet flows
with other flows instead of structures, and I'm not saying it can't be
done with enough time and money. But forgive me if I hear in your
optimism the ring of "Taming lions is dangerous, so I'm going to get
this tiger to do it..."

I hope you don't mind me top posting, I prefer it.

The development of computer models always follow the research that they are
trying to explain. Especially something that is still half a black art. To
me the proper approach is to go and do it, with a proper tool that allows
the subject to be explored properly. Building very expensive, one shot
experiments to verify our limited understand of the CFD models is not it.

WRT, Fluid Variable Intakes, turbulence is part of the problem, but the
majority of this problem is simply fluid manipulation, not ignition. The
CFD models are probably at a state to handle the majority of the problem,
which could be used to build a vehicle to carry the black art experiments.
Add some physicists, or aerodynamicists with the proper background to
search in the right areas to get the combustion right and come up with the
proper models. If one approach doesn't work quite right, swap out a few
parts and fly the experiment again. Experiments are the proper way to treat
black art subjects, not waiting for the CFD models to come first. Cheap,
easily modified experiments, not expensive one shot wonders.

As, I said earlier, there is a clear path of experimentation from turbojet,
ramjet and scramjet. Push the turbojet past it's normal range, then add the
scramjet running as ramjet and push it past it's normal range, then work on
the transition from ramjet to scramjet and finally start optimizing the
scramjet. The turbojet is running the entire time, providing the maximum
thrust it can, and probably providing almost all it's thrust from the
rocket equation at the end of the run. It's the Fluid Variable Intakes that
allows such a progression, and it's an acceleration type mission profile,
short duration experiments each optimized for acceleration, not endurance.

Throwing away the endurance mission profile requirements totally, in favor
of the acceleration mission profile requirement in the turbojet, ramjet,
and scramjet final designs too. IMO, the two different requirement sets
yield different end results. And personally, hope the endurance
requirements are abandoned...

As to the hypersonic engine mentioned, it's not an extention of the
scramjet, or a hypersonicramjet. The engine I'm talking is probably best
developed from the other end of the atmosphere and would meet the scramjet
somewhere in the middle of the atmosphere. I think an understanding of this
engine and how it works is important to scramjets used in acceleration type
mission profiles. It could also be use to go to the Moon and Mars. Might
even shorten the time to Mars by quite a bit.

Not a Taming of Lions, but more like a child learning to crawl, walk and
finally run.

**
Craig Fink
Courtesy E-Mail Welcome @
**


Monte Davis wrote:

You seem to have an exaggerated idea of our mastery of high-energy
fluid dynamics. It has always been *hard* stuff, and for all the
progress in computational FD it remains so. There is a reason why
physicists have been calling turbulence "the work of the Devil" for
150 years; it's where what we now call chaos first forced itself on
their attention, because very small irregularities tend to get big
very fast. There is a reason why predicting hurricane behavior is
tricky, why killing off combustion instability in rocket engines is
still half a black art, why tokamaks keep turning up fascinating new
ways for plasma to kink itself, etc, etc, etc.

It *sounds* cool as can be to shape supersonic-hypersonic inlet flows
with other flows instead of structures, and I'm not saying it can't be
done with enough time and money. But forgive me if I hear in your
optimism the ring of "Taming lions is dangerous, so I'm going to get
this tiger to do it..."

Craig Fink wrote:

Scramjets haven't had Fluid Variable Intakes attached to them yet. As the
speed of a Ramjet increase, so does the compression (area) ratio of the
Inlet. This can be done with Fluid instead of an all variable structure
solution. At the point of instability at the throat, where the air begins
to disassociate, the Fluid is turned off. The normal shockwave at the
inlet throat travels through the engine and out the nozzle, it's now
operating as a Scramjet. All done with the twist of a valve, instead of
complex variable structures.

On Sun, 15 Jul 2007 23:07:20 GMT, Monte Davis
wrote:

Scott Ferrin wrote:

My point was scramjet progress was derailed for
decades simply because of lack of interest.

Ummm... it might just possibly also have something to do with

(1) the limits of CFD -- already dicey around a scramjet inlet, and
worse in the combustion zone

ROFL!!! They were working on stuff LONG before modern CFD on a
computer came along. But scramjets, RBCCs, TBCCs, ramjets, LACE,
external burning, you name it, all got put on the shelf once they
started putting stuff into space with expendable boosters. NASA was
on the verge of testing a scramjet engine on the X-15 back in the day
and yet it takes them another 40 years to do it?



(2) the need for a rocket launch before you can even fire up your
prototype. There are Mach 10+ wind tunnels, but they're small and
limited to extremely brief "shots." Kinda slows down the
test-modify-test cycle...


Never stopped them before. It's not like you need to have an X-43 and
a Pegasus to test a scramjet. Australia seems to have been doing okay
using retired SAMs for boosters. Russia tested theirs on a SAM. It's
not like the US has been lacking for missiles to test with.

Scott Ferrin wrote:
Never stopped them before. It's not like you need to have an X-43 and
a Pegasus to test a scramjet. Australia seems to have been doing okay
using retired SAMs for boosters. Russia tested theirs on a SAM. It's
not like the US has been lacking for missiles to test with.


Lockheed built a test vehicle, the X-7, during the 1950's specifically
for testing ramjets.
Much like our cruise missile programs during the 1960's the ramjets got
put on the back burner, and the Soviets pulled ahead of us in ramjet
technology to the point where it became a common propulsion method for a
lot of their missiles.
The GELA ramjet test vehicle was working toward the type of intake
geometry needed for scramjets: http://www.aviation.ru/Raduga/Raduga.jpg
They also showed a scramjet vehicle at the 2001 MAKS air and space show,
called the HFL-VK:
http://www.russianspaceweb.com/topolm.html
Which may be associated with the Topol-M missile.
If we wanted to test out rocket boosted scramjets we could do it at
fairly low cost using decommissioned Minuteman boosters, or if the test
vehicle was small enough, even sounding rockets.

Pat