Banned
I wonder what the future is regarding hypersonic aircraft?I wonder if airliners will soon be travelling across the Atlantic at 5 times the speed of sound,or suborbital?surely there must be problems with friction that have to be addressed at that speed?
I still think it can happen one day...!!
just a thought
PL
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Once you get up into those speeds, it's probably as easy, if not easier, to go suborbital. Same launch. Only difference is how long you stay up before you hit the retros.
Established Member
The interesting thing thou is that the Concorde and the Tupolev Tu-144 were already at Mach 2 by the late sixties. One would have expected that by now Mach 5 and suborbital flights would be a norm.
Here is a wiki link to the Concorde
http://en.wikipedia.org/wiki/Concorde
and the Tupolev
http://en.wikipedia.org/wiki/Tupolev_Tu-144
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I would have thought the efforts of beauties like the SR71 would show that above a certain speed you really are into exotic realms and expensive at that. To get Concord up and running was a feat. Think what hypersonic speed would require? So why would manufacturers delve into this expensive aspect when they can make more with normal proven airliners?
Looks like a money pit until experimentation proves a way.
PS thinking aloud.
Last edited by Tedward; 2008-Jun-17 at 11:31 AM. Reason: Added ps
Order of Kilopi
Quite a lot of the research into these hypersonic engines and planes involves space agencies instead of / together with private companies.
Space agencies (and defense) can possibly also benefit from advances in these technologies for first stages or boosters of launchers.
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Lockheed-Martin seems to be working on civilian supersonic planes again, smaller than the Concordes because they didn't make much money because they often didn't have enough passengers.
http://content.techrepublic.com.com/..._11-30254.html
http://www.janes.com/aerospace/civil...0727_1_n.shtml
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Either way a civilian version need to get paying passengers on, whether or not governments subsidise it a tad.
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I'm currently rereading Ben Rich's book, Shunk Works. He was the lead thermodynamist on the team that developed the SR-71 engine nacelles and cooling systems. He had some rather pointed observations about the challenges of making a hypersonic airliner. The cockpit window of the SR-71 (at about Mach 3.2) was over 600 degrees Fahrenheit. They had to develop an elaborate cooling system to keep from baking the pilot - who was wearing a full pressure suit. The challenges of managing the heat loads on a hypersonic airliner filled with passengers wearing ordinary clothing would be much harder than what they did in the Blackbird and that was extremely difficult.
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Ah, looks a good book. On me list, thanks.
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It's a good book with a few minor errors/typos that are largely insignificant. Ben Rich came to the Skunk Works in 1954 from Lockheed's main plant to help design the air intakes of the U-2. He headed research into developing a liquid hydrogen powered reconnaissance plane before coming to the inescapable conclusion that it just wasn't feasible (at least not at the time). He was there for the development of the Blackbird and eventually became the head of the Skunk Works when Kelly Johnson was forced to retire at age 65. Rich headed the development of the Have Blue stealth proof of concept vehicles and the F-117. The book talks a lot about the challenges of pushing the engineering state of the art and managing complex projects on tight budgets and timelines.
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Definitely a wonderful book, and I would highly recommend it to anyone even remotely interested in aircraft.
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With increasing oil prices, don´t expect it too soon.
Banned
Suborbital you don't need retros. Just reentry.Originally Posted by Kaptain K
Works great for between 1/5 and 1/2 way around the globe. Any less than 1/5 and you never escape the atmosphere, or have too steep a reentry. Obviously, anything more than 1/2 way around the globe means you're heading in the wrong direction...
I say the last in jest, as the Earth spins 1,000 mph at the equator, which means it may be as efficient to travel eastward 3/5 of the way around the globe, suborbitally, as it is to travel 2/5 of the way heading west, again, suborbitally.
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To go sub-orbital without retros means both altitude and velocity must be controlled to within meters/meters per second. Using retros is vastly easier. Just use a generic (near)orbital path and pull the plug at your exit!
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That takes FAR more delta v initially though than a ballistic path planned to reenter near your destination, especially if you aren't going anywhere near halfway around the earth (but still far enough to make suborbital practical, like 1/4 around or so)
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It might be fun, but I think hypersonic passenger travel is simply acedemic now.
Jet A is $5.50 and better.
The game is carrying the most amount of passengers for the least amount of costs. You will probably see a blended wing . I don't see trans sonic jets
doing passengers. Concorde had the prestige of not making money. That is not exactly high praise.
Best regards, Dan
Administrator
I get the impression that when he was saying retros, he didn't mean go to orbital velocity and then slow down, but rather that he thought some rockets would be useful for above the atmosphere maneuvering.
For my part, I don't think a suborbital passenger flight would be any harder to target than an ICBM. Like it or not, we seem to have the technology to land a warhead in a space smaller than an airport. I expect civilian usage of the targeting technology wouldn't that hard to arrange.
Forming opinions as we speak
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From charts I saw when I was in the Air Force, the total velocity required to fly an ICBM warhead over 6,000 miles is very little different than that required to put the warhead in orbit. The biggest difference is the trajectory, not the velocity. Flying passengers on a ballistic trajectory on trans-Pacific distances would be almost as difficult and expensive as putting them in orbit. It would have a much lower heat-loading problem than cruising at hypersonic velocities inside the atmosphere. However, you're basically talking about a single stage to orbit vehicle, something that history and the rocket equation show is very difficult to achieve.
In his book, Ben Rich stated that he didn't believe a hypersonic airliner would be possible before 2050, if then. The heat load challenges alone make the project far more difficult than what they faced developing the Blackbird.
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We paid for, lived with and enjoyed the problems associated with Blackbird.....
because we had to. Different game.
SR-71 takes off with little fuel, climbs to altitude and begins re-fueling.
Blackbird drinks......often and much.
Best regards, Dan
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...and leaks like a sieve until it reaches operational temperature!
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Wouldn't a "ballistic" flight deprive the occupants of the effects of gravity?
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Yep. Major wheeeeeee factor!
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Wouldn't a "ballistic" flight deprive the occupants of the effects of gravity?
Yes, and given how many trained astronauts suffer space sickness until they acclimate, I wouldn't want to be part of the cabin cleanup crew after each flight. You have to also wonder about the G loads the passengers would have to endure during reentry.
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So, it seems we´re left to work out something à la SR-71...
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So, it seems we´re left to work out something à la SR-71...
If you have not already, I urge you to read Ben Rich's book, "Skunk Works". The challenges they faced developing and operating the Blackbird were huge. While technology has improved since the early 1960s (the first Blackbird flew in 1962!), the physics is the same. Rich specifically talks about the fundamental challenges of the "Orient Express" hypersonic airplane and the National Aerospace Plane proposed during the Reagan administration.
Just as a comparison, the Blackbird required special fuel, special engines, special alloys, special air tanker support, and a huge effort to move one or two men in space suits (A-12 was a single-seater) above Mach 3 for about 3,000 miles before needing refueling. It would be vastly more difficult to build an airliner that flew hypersonically (above Mach 5) for longer distances carrying a load of passengers in ordinary clothes.
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Actually, I just ordered it from the link you suggested.
Yeah, I understand. But how do you cope with the problems of a suborbital flight in practice? It seems to me that new materials in the coming decades could minimize the problems you describe for an hypersonic plane. What do you think?The challenges they faced developing and operating the Blackbird were huge. While technology has improved since the early 1960s (the first Blackbird flew in 1962!), the physics is the same. Rich specifically talks about the fundamental challenges of the "Orient Express" hypersonic airplane and the National Aerospace Plane proposed during the Reagan administration.
Just as a comparison, the Blackbird required special fuel, special engines, special alloys, special air tanker support, and a huge effort to move one or two men in space suits (A-12 was a single-seater) above Mach 3 for about 3,000 miles before needing refueling. It would be vastly more difficult to build an airliner that flew hypersonically (above Mach 5) for longer distances carrying a load of passengers in ordinary clothes.
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I think that suborbital flight would be easier by far to cope with - the temperatures at reentry are higher, but not nearly as long of duration, and I think 2500+ degrees for a few minutes is more realistic to expect anytime soon than 1500+ degrees for hours. That isn't to say it couldn't be done of course, but I can't see the problems associated with a hypersonic airplane being solved soon. Of course, there's also propulsion (for both cases).
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But what would it do to the women´s hairdresses?
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Let me just say that we encounter some massive problems with hypersonic jet planes, but we're not at the point that we must conclude "impossible now or in the near future, unless we invent something magical thisorthat". So research continues. The heating problem could be solved with another problem: the huge amount of very cold fuel on board. Of course such a system has its own problems. Or let's call them challenges.
It's all very hard, but very interesting too and with potential.
I may have said it before, but supersonic and hypersonic jet engine design isn't engineering, it's a scientific art. Sometimes, the interaction patterns of shock waves and the engine are so beautiful, especially when you know what you want to see and it's there in the picture.
I don't know whether we'll have hypersonic passenger planes say in the first 15 years. The problems are quite large. Even at the theoretic design stage, it's not easy to find a working solution. Chances are, IMO, large that we'll have hypersonic engines and applications other than passenger yets within 15 years. I can say we'll certainly have hypersonic engines eventually, and I'm quite confident passenger transport will become one of its applications. But it may not be for the near future. Even if the engine works, you'll have to drag huge amounts of fuel (hydrogen, m³...) according to the current designs.
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It's most unlikely that we'll have supersonic airliners in the next 15 years (say Mach 1.5 - 2.0), much less hypersonic airliners (by definition, hypersonic > Mach 5). After spending over a billion dollars on research, Boeing concluded that the technology to produce a profitable, long-range supersonic airliner that didn't trash the environment (a relatively new constraint) was simply too far beyond the current or foreseeable state of the art.
For super high speed transport, two different concepts have been mentioned in this thread - hypersonic cruise and ballistic. Each approach has advantages and disadvantages.
Hypersonic cruise advantages include:
1. Lower total velocity requirement (long range ballistic flight is almost as fast as orbital velocity) while Mach 5 is in the 3200 MPH area.
2. More flexible operations (e.g. ability to enter into a holding pattern if traffic/weather conditions dictate)
3. No weightlessness with associated barfing
4. No high-G reentry loads on the structure, passengers, and crew
5. No "single stage to orbit" style constraints on the design (see rocket equation)
6. Lighter take-off weight (but may require aerial refueling - still fairly dangerous for passenger operations)
Ballistic advantages include:
1. Lower total heat load than sustained high speed cruise in the atmosphere
2. Technology lends itself to the development of reusable space boosters
3. Increasing range requires relatively little additional velocity (you don't have to go much faster to fly 8,000 miles than you need to go 6,000 miles)
Both are well beyond the current state of the art. Given the high costs of R&D and energy as well as the dismal financial state of the airlines, I just don't see either of these being developed in my lifetime (currently aged 51).
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