NASA 'Hyper-X' Series Scramjets 58
swight1701 writes "Sciencedaily.com is reporting that NASA has revealed its plans for developing Hypersonic aircraft within 2 decades. These plans include planes that could routinely go Mach 5+ and capable of taking off from an airport and visiting the IIS, or for you earthbound folk, from one airport to any other within 2 hours. And you thought your luggage gets lost NOW.:)" NASA's release includes some graphics showing what the test vehicles look like.
How do they see? (Score:2)
Re:How do they see? (Score:5, Informative)
Any useful window has to have a large area projected to a plane perpendicular to the direction of travel. This would mean an extremely large window because of the wedge angle at the front of the plane. And this angle is required to be very small to keep the losses associated with the bow shock from becoming astronomical. The faster you are going (relative to the speed of sound) the smaller that angle must be to keep the shock attached and oblique.
The really interesting stuff on this craft is the engine inlets, the entire plane is designed to minimize engine inlet losses, due to shocks. Cool stuff
Re:How do they see? (Score:1)
decade or two from now, the entire hull could be
made of synthetic diamond. Strong, lightweight,
conducts heat really well, and transparent...
Re:How do they see? (Score:1)
Re:How do they see? (Score:2)
Re:How do they see? (Score:1)
They said they may be able to visit the _IIS_...
Re:How do they see? (Score:3, Funny)
Re:How do they see? (Score:1)
Re:How do they see? (Score:1)
Nasa getting back to high tech. (Score:2)
Visiting the IIS... (Score:4, Funny)
If I want to visit the IIS, I'll just go into the computer room, thank you. Oh, you mean the ISS...
Re:Visiting the IIS... (Score:3, Funny)
12.34.56.789 - - [28/Feb/2002:05:44:58 -0500] "GET
>:)
It's HUGE! (Score:2)
Re:It's HUGE! (Score:1)
Re:It's HUGE! (Score:1)
Re:It's HUGE! (Score:2)
The X-43B is much larger, for sure, and is not powered by a pegasus, but it is still going to be dropped from either a B-52H or an L-1011. Probably the B-52H which Nasa just acquired from the USAF.
Now, when you start talking about single stage to orbit vehicles with combined cycle engines designed to carry freight cheaply,you will be talking about aircraft 200 feet long weighing upwards of 1.5 million pounds. Anything less and the incredible inefficiencies of fixed structure cause your useful cargo load to be negative (I could write a whole lot more about this, and may, later, but it is going-home-time now
Neh
aero geek
May I ask... (Score:1)
Re:May I ask... (Score:4, Informative)
Re:May I ask... (Score:2)
Another way is to build the rocket engine into the Scramjet but that's much more difficult.
Re:May I ask... (Score:2)
Probably not. The problem is you need extra equipment to breath the air- and you carry that all the way to orbit. It turns out that's really critical- you gain most of your speed as the tank is running out (because your fuel level is low and the vehicle is really light then, so you get better acceleration per unit of fuel at that point). And you're in a vacuum, so this equipment doesn't help at all at that point.
Adding in extra mass for airbreathing means that the latter part of the launch is messed up- and so the designs to do this have not succeeded well- they end up using more fuel not less, and/or the payload ends up being really tiny.
Also, you're probably solving the wrong problem- the fuel is less than 1% of the cost of building and launching a space vehicle.
Re:May I ask... (Score:1)
Re:May I ask... (Score:2)
The problem is that because the shuttle is man-rated, they basically have to take it apart and put it back together again to make sure everything still works. This costs a _lot_. Fuel is cheap, but shuttle parts and skilled engineer time are not.
A secondary problem is that the cost of maintaining all of the facilities for servicing the shuttle must be amortized over the (relatively few) shuttle launches. This too is very expensive.
The main reason why finding more effective fuels is important is that they let you reduce the total craft size and weight for a given payload weight. This makes the craft much cheaper to build and maintain, reducing the cost of lifting the fixed-weight payload.
Re:May I ask... (Score:3, Interesting)
Your numbers are a bit off BTW. The cost to launch a man is generally reckoned to be about $10,000 per kg. The russians charge less than $20 million, basically because they can. Their whole rocket costs about $5 million. There's a big difference between cost and price...
The real cost goes into the salaries of the employees. There's about 10,000 or more involved with the Space Shuttle. But don't get the impression that the Russian rockets are cheaper just because the Russians are paid a lot less- they are, that's a big factor, but the way they put their rockets together is more efficient as well. NASA don't seem to care about low cost in quite the same way.
Please don't mention the external tank... it gives me a headache just thinking about that much waste.
SLI? Hah!
Re:May I ask... (Score:1)
Re:May I ask... (Score:2)
google cache [216.239.35.100] You'll see the cost per kg of liquid hydrogen was $2.60 in 1980. I expect it has gone up since then, but not so very much; and it does vary a bit- e.g. if you order enough hydrogen the price goes down.
The Space Shuttle's main tank contains 101 tonnes of liquid hydrogen. Assuming a price of $5/kg, that's $505,000 worth of hydrogen (since there are 1000kg to the tonne). Right?
The cost of adding an extra Space Shuttle to the yearly launch manifest is about $200 million.
Congratulations, you have just learnt something!
Oh yeah the Space Shuttle also burns 606 tonnes of LOX. LOX costs vary, but they are typically a few cents per kg. You can multiply that up if you wish, but the costs are more than 10x less than the hydrogen.
Re:May I ask... (Score:2)
About your cheap fuel point, you're missing the problem of weight. Yes, the fuel is cheap. Getting the fuel to 100,000 feet with a rocket is not cheap. Rockets are not the most efficient propulsion system. They are needed in space because nothing else works.
I'm not an expert. If you are, I'll concede the point.
Re:May I ask... (Score:2)
Yeah, that can work. But then you've got a two stage rocket; which is messier. Anyway they already do that- with a normal jet- the Pegasus launch vehicle carries a rocket up and then fires it from there.
About your cheap fuel point, you're missing the problem of weight.
That's mainly an issue with ground handling I think.
Yes, the fuel is cheap. Getting the fuel to 100,000 feet with a rocket is not cheap.
Actually it probably is, it mostly just costs fuel, but fuel is cheap.
Rockets are not the most efficient propulsion system.
Thermodynamically a rocket is the most efficient propulsion system. It can turn practically all of the energy in the fuel into fast moving fluid flow. It's more efficient than jets because it runs at incredibly high temperatures. However, jet engines can get more total thrust ('impulse') per unit of fuel because they suck in the oxygen from the atmosphere. If you count that in; Jets are less efficient in fact.
I'm not an expert. If you are, I'll concede the point.
It's not that the idea is silly, it's just that the constraints on it are tight enough that nobody has managed to get it to work well.
Re:fa! (Score:2, Insightful)
But now rockets tend to get the job done more often than not. This new thing might be 'an airplane' but it's still a new thing and new things tend to not work the first time. There's process called learning involved. Sometimes, alas, it is terribly expensive.
Stupid designs. (Score:2, Insightful)
The correct model for spacecraft is to take off and land on a tail of fire, as God and Robert Heinlein intended. The DC/X proved that; 11 successful test flights, including an 11-degree 'walking tilt', before NASA took over that program and (deliberately?) crashed the prototype on their first try with it.
Re:Stupid designs. (Score:3, Interesting)
One of the ways around this is to use plasma. If you generate plasma ahead of an aircraft with a welding-torch type of thing, you can reduce the drag by as much as 30%. The Russians are using plasma in their next generation of MiGs. (BTW, plasma also absorbs radar)
Another thing is to use carbon-carbon composites. C-C's are very expensive but can withstand many thousands of degrees. They are used in rocket nozzles.
Re:Stupid designs. (Score:1)
The plasma thing sounds really cool, until you think about it. After the first couple of MiGs come apart in mid-air, I'm sure the Russians will scrap that idea.
Re:Stupid designs. (Score:2)
You get the same effect with a gas blanket, which is a lot easier to produce than plasma. However, this is still a pain in the neck, making your craft vastly more complicated and requiring considerable fuel if the wings have any significant cross-sectional area at all (to spray the gas blanket [most likely an exhaust stream] forward fast enough to move the shockwave off the wing edge).
A better approach would be a) making the wing angle very small, so that you have a lot of leading-edge area per unit cross-sectional area, and b) only going at hypersonic speeds when you're in very thin atmosphere, reducing the amount of heating.
As for carbon composites, while graphite won't vapourize until about 4000 degrees C, it'll be rapidly etched away unless you coat it with something. "Something" is tungsten carbide, for the shuttle, at least. That has a melting point of around 3000 degrees C, and may or may not start degrading at a lower temperature (ask an aerospace engineer). Carbon composite shielding can take a lot of punishment, but _gliding_ at orbital velocity in an atmosphere overwhelms it unless you have a very light craft. (Important number is effective pressure exerted by the air you're plowing through, which is proportional to the craft mass, and which rate of heating is directly proportional to. You can play with the proportionality constants [by altering craft geometry and materials] to make the problem less severe, but a lighter craft will always help and the problem is always bad at high speeds).
The obligatory post-9/11 questions... (Score:1)
2) How do you intercept one that has been hijacked?
Re:The obligatory post-9/11 questions... (Score:1, Funny)
Wow, new airplane designs! (Score:3, Interesting)
Ozone Layer? (Score:2, Interesting)
Vapourware (Score:1, Informative)
PULSEJET: Combines Air Breathing and Rocket (Score:5, Interesting)
Just some ideas.
ALSO: How come we don't see postings on Nasa websites with "what we've considered and why it didn't work" so outside engineers can solve their problems for them...
Re:PULSEJET: Combines Air Breathing and Rocket (Score:1)
Re:PULSEJET: Combines Air Breathing and Rocket (Score:1)
Lets think about this for a moment... (Score:2, Informative)
Lets think about the plane that closest fit the bill, the SR-71.
It was capable of mach 3+ and flew at an altitude of ~120,000 ft.
It was made completely out of titanium and the body of the plane got so hot that the pilot had to wear a space suit and couldn't touch the cockpit glass. The plane leaked fuel on the tarmac because it had to be designed with gaps that would close once the frame expanded from the extreme heat. In order to maintain mach 3, it had to run at full afterburners, burning a special fuel that had a super high temperature of ignition. And this was so it could carry 2 guys and a camera.
See the problems I have with this? Now granted, I'm not an airanotical engineer by any stretch of the imagination (or literate for that matter, based on my inability to spell...)
It was hard enough to get a moderately large plane going mach 3, now imagine what kind of energy you'd have to exert to get something the size of a 737 going?
Just my thoughts...
Re:Lets think about this for a moment... (Score:1)
Re:Lets think about this for a moment... (Score:2, Interesting)
http://www.x15.com/program.html
"The X-15 was carried to an altitude of 12,000 meters (40,000 feet) under the wing of a Boeing B-52 bomber. During one test, it attained an altitude of over 108 kilometers (67 miles), flying so high that it functioned more as a spacecraft than an airplane. In 1967 it reached Mach 6.72 (7,297 kilometers or 4,534 miles per hour). "
http://www.hq.nasa.gov/office/pao/History/SP-60
http://www.wpafb.af.mil/museum/modern_flight/mf
http://www.astronautix.com/craft/x15a2.htm
Didn't they already try this... (Score:1)
Re:Didn't they already try this... (Score:1)
Gas Tank (Score:1)