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Space Plane to Offer 2 Hour Flight around the World
secretsather writes "Two hour flights to the other side of the world may seem like a scene from a science fiction movie; but the technology is in place, and a plane that can do just that is currently in development. While it looks like a scene from a flight simulator, the Astrox space plane is the real deal, and the Astrox Corporation says it could revolutionize the transportation industry. Traveling as fast as Mach 25 with at least 30 minutes of space shuttle-like views while in orbit is the highlight of this plane, and The Astrox Corporation, along with their partners, are claiming to have finally overcome their largest problem, mixing fuel."
Well, let's see. x=(a t^2) / 2. Let's say a = 3.2 ft/sec^2 (1/10 g), so we're not talking real heavy acceleration here. t = 1 hour = 3600 seconds. (We'll use the other hour to decelerate.) Then...
x = 20,736,000 feet = 3927 miles. The whole, two hour flight would be 7854 miles. Not quite halfway around the world (12000 miles).
To do halfway around the world in 2 hours, we need to get 6000 miles = 31,680,000 feet, accelerating from zero, in 1 hour = 3600 seconds. For that, we need a = 2x / t^2 = 4.89 ft / sec^2 = 0.15 g.
Whether that's too much to be comfortable or healthy, I don't know.
Jetlag isn't about acceleration per se - it's about desynchronization of your circadian clock with that of your surroundings.
I can get you jet lagged by putting you in an isolation suite and resetting the clock you pay attention to, no acceleration involved.
That being said, the human body takes about a day to resynchronize from a shift of an hour.
I suppose you need to accelerate to get that far that fast if you do it by travel, but you can put away the equations that figure the precise acceleration of this plane to discuss jet lag.
"Win treats sysadmins better than users. Mac treats users better than sysadmins. Linux treats everyone like sysadmins."
The V-1 actually used a pulsejet, not a ramjet. Pulsejets have been built that work when stationary (some R/C aircraft use them as a substitute for a turbojet or ducted fan), and their maximum speed (Wikipedia says the V-1 reached 390mph) is about that at which many ramjet designs start working.
Thrust isn't the issue here, the problem is getting the combustor to work at any speed above mach 1. Various existing planes go supersonic with engines that slow down the supersonic airstream before using it for combustion. This works, to a point. Past a certain point, the pressure and heat build up and either melt or explode the engine. On the Blackbird, for example, bypasses are built into the engine to vent a good portion of the air from the compressor; slowing down a mach 3 airstream creates so much heat and pressure that it would melt the titanium engine. To get to the high mach numbers mentioned, the engine needs to maintain supersonic flow throughout. Getting fuel to mix into a supersonic flow and burn at a given spot is tricky, and it's the current focus of scramjet research. These folks are using a mach 2 wind tunnel because the main issue is that the air is going supersonic, not exactly how supersonic it is going, and generating a mach 10 airstream to test in would be pretty blasted expensive.
"Because Science" is one step from "Because old book". Try "Because of my experiment testing my falsifiable assertion".
And none of them are going to. One of the limitations of scramjets (and the earlier ramjets) is that they have no static thrust: they have to be hauling considerable ass before they'll even start up. They have to serve as auxiliary propulsion for a vehicle that is launched by something else.
rj
Yes, and this is how long it takes me to get from D.C. to Chicago. It would be way cool to end up on the other side of the world in this amount of time :-)
The discussion might have been a lot better if the article (or rather the blog entry) weren't so sorely lacking in details. Kind of makes me miss Roland Piquepaille. You can get a lot more information by Googling "suborbital airliner."
The blogger suggests that this vehicle is basically a very fast airliner, but this is far from the case. It's a sub-orbital craft that would fly on a parabolic course, thrusting up out of the atmosphere and then coasting the rest of the way. What makes it economically feasible is that a brief, steep climb uses less energy than horizontally plowing through the atmosphere for hours. Most proposed designs use a two-stage launching system. One calls for the airliner to climb to about 50,000 feet and do a midair refueling from a tanker. In another the airliner is carried up by a larger plane and released. In either case the airliner then goes into a steep climb for about 20 minutes and then shuts off its engines, coasting until it nears its destination. It would carry only enough fuel to maintain a holding pattern in case of airport traffic.
Passengers would be strapped into their seats for the entire flight. No food or beverage service, no restrooms. People most likely will take some sort of medication to avert motion sickness, as they would be weightless for much of the flight. There is a lot of research going into the human factors such as the several Gs acceleration and dealing with weightlessness. The bit about space-shuttle views of Earth kind of mystified me, because in all the designs I've read about there would be no windows. Maybe they were talking about view-screens.
It's a pretty interesting subject, and almost certainly will be the way we will fly long distances in 20 or 30 years.
At the compression ratio achieved by a scramjet, I don't believe the thin atmosphere is a problem. Effectively, the shock wave compresses the air for you.
However, the X-43 was a very, very far cry from a commercially viable transport. It was 12 feet long and had something like a 100 pound usable payload, dedicated entirely to instrumentation. It was a single use, throw away, test plane. The engine only ran for just over 10 seconds (the goal was not to accelerate the plane to Mach 10, but to prove it is possible to operate the engine at Mach 10...imagine a candle in a hurricane). It required a $30 million Pegasus rocket to accelerate it to stated speed. When NASA first started toying with scramjets, they created the X-30 concept, which would've been basically what the article is describing but more realistic. Then they got to look at actually making a scramjet work and haven't really talked about the X-30 since. The X-43 is far less ambitious, but is still a tough project.
Aside from the very substantial technical hurdles, what do you think the commercial market is for a 2 hour flight to anywhere in a cramped capsule moving so fast that if there were an accident, there might not even be teeth left to identify you with? Even the Concorde couldn't pay for itself, and it cut the trip time for a very busy route in half. For comparison, Virgin Galactic is planning on offering suborbital joyrides that peak out at 3000 mph and don't actually get you anywhere for $200,000 each. Supposing that $200,000 per ticket were achievable, I doubt anyone can justify saving 10 hours at that price, even really important business executives. Even if they're time were that valuable, it's not like they couldn't get work done in the air on a suitably equipped business jet.
For the full defencetalk.com article that this GoogleAds blog entry seems to be summarizing, go here . Lots more information. Found the link on Fark don'tcha know.
Been there, done that, got sick afterwards =)
.. oh well, you get the idea =) on our group and apparently she sort of got her ribs/lungs squashed between the weight of her breasts and the wall she was standing against, which made breathing difficult! Logical if you think about it, but I would never have thought about it upfront.
The problem wasn't that the forces due to the acceleration were too hard to handle, but the spinning DOWN made me nauseous because of what was happening in my inner ear(s). I also clearly remember that the 'world' look 'tilted' once the thing had spun up... It was kind of fun as an experience, especially when trying to fight the centri-something force. But I must admit I stay clear from them now... oh well, maybe I'll give it a try sometime later, when the kids grow up and I have to act the cool dad =)
>> The biggest problem would probably be obese people.
Actually, we had a 'well-breasted-lady' (otherwise slim, think Heidi Klum but 20cm smaller, and with black hair, and not as famous, and
If there is one thing to be learned on slashdot, it has to be sarcasm.