Why go to Norway ?
If you are from Queensland an want a large desolate area to drop a Mach8 brick onto?
Queensland's SCRAMSPACE research scramjet has arrived in Norway for a test launch to be scheduled somewhere between September 15 and September 21. Given that the project has gone from origins in the “back of a truck” (in leader Russell Boyce's earliest HyShot experiments) to a research effort worth $AU14 million, the …
You've missed 3 things...
Firstly the drag factor which means it'll take longer to accelerate (though not by much initially).
Secondly the fact that gravity is not constant - earth being an oblate spheroid, gravity is stronger at the poles, but is also weakens with altitude (and they're intending to go a long way up).
Thirdly, and most importantly, they're not using gravity to accelerate to mach 8. They're using gravity to accelerate to a speed where the scramjet will work. The rest of the acceleration will be jet powered!
Oh come on. Gravity may be detectably different at the poles but really this is not a factor in doing rough sums. And they are not going a long way up - the Earth's radius is ~6400km so they are only going to be 5% further from the centre of mass than you are right now. Again, measurable but pretty minor.
Oh look, an engine that... doesn't work until it's going really fast. That's useful.
Oh, wait, it IS useful... as a weapon. Very high speed missiles. Bombing the cr*p out of somewhere when it takes a couple of hours for your tomahawks to arrive just isn't any fun, it seems. Gotta have it there in 10 minutes or less or your next hard-on's free.
And in the meantime, there's little research into reusable rocket engines, cheaply-manufactured rocket engines etc because... yep, you've guessed it, scramjets are the new 'sexy' thing that's sucking down all the research money.
The point of a scramjet is that it's a jet. It uses atmospheric oxygen instead of stored oxidiser that it would have had to carry with it, thus making for a much lighter vehicle with greater range/payload.
Yes, it does need to be accelerated to a ludicrous speed before it works, but here's one (non-military) scenario where it can really help:
Three-stage orbital rocket:
First stage: Traditional rocket. Fuel and oxidiser stored in rocket. Gets whole vehicle up to scramjet speeds.
Second stage: Scramjet. Only needs fuel, saves weight on oxidiser.
Third stage: Ok, we're out of the atmosphere now, so we have to go back to rockets. But we have still saved the weight of the oxidiser in the second stage, and that effectively allows an equivalent increase in the payload.
Oh, that's right, this story is missing the obligatory statement about how this technology can be used to make airline travel faster, letting passengers arrive much sooner. (And of course when they say "airline" they mean "missile", and when they say "passenger" they mean "warhead". But you already knew that.)
Which may leave the American's slightly miffed, given they are much better funded.
SCramjets back a great research subject but their practical uses seem pretty limited. They are very far below the flight readiness of a regular (subsonic combustion) ramjet and take a lot more grunt to get to working velocity.
TBH if you were looking for a useful ramjet research programme you'd want to a)Widen their operating Mach range (realistically it's about 3 Mach numbers and has been since the '50's). Widening this would mean a smaller booster to get to the same high operating speed. EG A M5 ramjet needs a M2 booster to get to ignition speed would now need a (much smaller) M1 booster.
b) Lower the amount the inlet has to be slowed down before reaching the combustor. Historically that has been to M0.5, but raising that to say M0.9 or M0.95 would lower the drag losses quite a lot (and the amount of heat the airframe has to absorb doing so), and since it's it's already pretty hot ignition should not be a problem.
So thumbs up for the Australian effort but I won't hold my breath this is anything close to flight ready.
Lower the amount the inlet has to be slowed down before reaching the combustor. Historically that has been to M0.5, but raising that to say M0.9 or M0.95
Surely the "SC" bit of SCRAM jet means that they don't need to slow the air to below Mach 1 for combustion?
"Surely the "SC" bit of SCRAM jet means that they don't need to slow the air to below Mach 1 for combustion?"
I was talking about a useful ramjet research programme.
That's something that would give a flight vehicle, or vehicle upgrade, within 5 years.
The first SCRamjet tests were done under classified USN Programmes at the APL of Johns Hopkins in the early 1960's.
We are still waiting for an actual application vehicle to fly.
My prediction is (funding permitting) Skylon will be in service and flying to orbit before this idea gets anywhere close to a working flight test vehicle.
@John Smith 19
This is useful supersonic ramjet research. Who knows what will come of it? No-one really. But isn't that the point of research? Some of it results in stuff, some of it doesn't. Since no-one has really got a SCRAMJET to work well yet (despite these tests in the 60's? Really?), surely any research is almost by definition, useful.
"This is useful supersonic ramjet research. "
I'm sure it will increase the number of PhD's in hypersonic flow. Some may even find work in the field as well. That would not include yourself by any chance?
"Since no-one has really got a SCRAMJET to work well yet (despite these tests in the 60's? Really?), "
Yes really. The work was finally de-classified in the late 80s when the AIAA released a history paper on it. The first time even a small vehicle achieved positive thrust IE switching on the engine speeded the vehicle up was around 2010.
And yes the US X30 was basically built around one of these. Something over $1Bn they discovered a)They should have checked the Principal Investigator had used the right values for basic physical constants and b) It's damm tough and pretty much anything else is simpler.
If you want to play the conspiracy theory card I'll simply say that if the US had got it working decades earlier (which is what your implying) they would have either not bothered to fund this or focused it in areas away from such technology.
I recommend you go away and down load TA Heppenheimers "Facing The Heat Barrier."
Isn't that a hospital?
Ah. Hang on. Now we've got Aussies in the act. It's not missile research. It's all about getting the Flying Doctor to the well in the outback that little Bluey fell into and which Sippy has just hopped for three days to the nearest mobile phone mast where he could twitter the message from?
"What's that you say Skippy?...."
-----> Yeah, the one with the front pouch.
So if the autodestruct doesn't happen.
What is a mach 8 rocket going to do to the sea.
1. Enter like a diver and do little else?
2. Make a big ripple?
what it will do is create a very large radioactive cloud
Whoops who forgot to remove the live nuke war head
"I'd have thought that the speed would drop fairly rapidly as the friction with the air built up - true, momentum will probably keep it above terminal velocity, but I doubt it would retain enough to hit the water at Mach 8."
Wrong. 320 Km is roughly 1.05 million feet.
Like the Swiss skydiver. Almost no air --> almost no drag.
Vehicle picks up speed. Not sure it'll get up to SCRamjet ignition speed in free fall on its own, But I'll take their word for it.
When it hits dense air OTOH....
"As John Smith 19 points out above, almost no air --> almost no drag, so yes they are relying on free fall to get it to Mach 8. "
I finally applied Newton and yes, in principle, most of that fall speed can be gained by a straight free fall from that altitude. I'm guessing htat saves them the cost of a booster rocket pointed down (yes that has been used before) to increase the speed. I think there will be some thrust produced and they get to study it's flight from 0-M8, which is difficult if you go from +x 1000s mph up to -x 1000 mph down.
Hopefully they will get positive thrust when it fires (that's not guaranteed. They only started getting thrust in 2004).
One thing they did not mention was (if they have someone on the water) they will get some great data about what does happen when an object at M8 hits the water.
Short answer. There will be one hell of a bang and water plume (for such a small object) as it transfers its kinetic energy to (a lot of) water.
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