Posted on 03/09/2010 10:16:28 PM PST by ErnstStavroBlofeld
The U.S. Air Force is gearing up for the first of four planned test flights of a hypersonic aircraft designed to operate for much longer durations and cover far greater distances than previous platforms of its type.
The maiden flight of the X-51 Waverider aircraft — the first U.S. hypersonic vehicle to fly in six years — is scheduled to take place later in March. Boeing Defense, Space & Security Systems of St. Louis has been developing the aircraft since 2003 on behalf of the Air Force Research Laboratory and Defense Advanced Research Projects Agency.
The missile-shaped X-51 will be carried aloft under the wing of a B-52 bomber, Joe Vogel, Boeing's director of hypersonics, said in a Feb. 22 interview. It will be released from the jet over the Pacific Ocean and drop for four seconds until its rocket motor ignites and accelerates it to about 5,800 kilometers per hour, just shy of the widely accepted start of hypersonic flight at Mach 5, or about 6,100 kilometers per hour. At that point, its air-breathing scramjet — or supersonic combustion ramjet — engine, built by Pratt & Whitney Rocketdyne of Canoga Park, Calif., will kick in, shooting the craft to Mach 6, or more than 7,400 kilometers per hour.
(Excerpt) Read more at space.com ...
I’m aware of that...I was thinking that the momentum of the plane moving in a straight line could keep it moving upward, especially as the friction of atmospheric pressure & gravity decrease as the plane’s elevation increases.
Speed is necessary to overcome the effects of gravity. Throw a ball. It travels along an arc (a parabola) and then hits the ground. The harder (i.e. faster) you throw it, the further it goes before it hits the ground. Now imagine that you could throw that ball a mile; two miles; three miles. Each time you would have to throw faster and faster. Now imagine that you could throw that ball 500 miles. It would land out of side, somewhere beyond the horizon. The arc that the ball follows would begin to approximate the curvature of the Earth. Now imagine that you could throw the ball so fast that it doesn’t just disappear over the horizon, it keeps falling around the curve of the earth. At that point, the ball’s in orbit. It has just achieved escape velocity. This is why high speed is necessary for space flight.
Very well explained - accurate - complete - easy.
...not a stupid question at all. Imagine some of the things that could be done in warfare with it.
Imagine something much faster than our current ICBMs.
I can imagine a kinetic energy missile, no warhead needed.
//I mean, if I could fly a Piper Cub in a straight line up to a height of, say, 25,000’//
Hmm, a little unclear on the concepts I say ;-) So many places to begin.
Yes. The thin air will cause your engine to conk out.
Actually, you could just keep flying your Piper Cub in a straight line all the way up to space if you wished, and never have to reach escape velocity.
You would, however, (barring the minor problem of oxygen for your motor, and air for your propeller to act against,) require enough fuel to keep your motor running for the entire time you wish to be in space.
Another way to say it is that in the same way that a helicopter hovers by constantly pushing against gravity, you could have a rocket that lifted you at a very slow speed, constantly pushing against gravity, and make it to orbital height.
As soon as you turned off your engine or ran out of fuel, you'd fall back to Earth, even if you were thousands of miles high.
This is exactly what Bert Rutan did with SpaceShipOne.
He had just enough fuel to reach 100 miles in altitude at zero velocity.
You asked if the Earth's gravitational pull on the plane would diminish the higher you go. Well it does, but by only by fractions of a percent.
That's what keeps the Moon from flying out into space!
Orbital velocity is less than escape velocity. Escape velocity is the speed necessary to esacpe gravity, while orbital velocity is what is required to "balance" with gravity.
1) Your piston engine quits working. The air is much thinner up there than sea level.
2) Your wings quit working. Again, the air is much thinner up there than at sea level.
You need to cram enough air down your engine's throat to make it work. Speed helps.
The atmosphere becomes thinner as you gain altitude. The wings on you hypothetical Piper Cub would lose their ability to lift you futther after a certain altitude. Also, the naturally aspirated engine of you Piper would not be able to “breathe” after a certain altitude.
Higher altitudes require an aircraft to have higher velocities to maintain sufficient airflow over the airfoil to generate lift. Also, your wing area is a factor.
Aircraft carriers are becoming sitting ducks. If one of these missiles were shot directly down from space towards an aircraft carrier it would have only seconds to intercept it. Maybe with a laser or particle beam cannon, a few seconds might be enough.
Gravity doesn't decrease as fast as you think. Zero gravity in low Earth orbit is an illusion caused by the spacecraft falling fast enough to match the pull of gravity. Really the gravity pull is nearly as strong as it is on the surface.
I like it. There are a lot of these already, they are somewhere in between the orbit of Mars and Jupiter. The only thing is that getting them to target our enemies is very difficult.
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