Forgive me for my ignorance here, but I have a stupid question:
Why is supersonic speed necessary to be able to venture into space?
I mean, if I could fly a Piper Cub in a straight line up to a height of, say, 25,000’, what would prevent me from going even higher, especially when you consider the fact that the earth’s gravitational pull on the plane will diminish the higher you go?
I’m just curious, OK?
The thinner the air, the less lift, less oxidizer, less progress until stall. I think you forgot the /sarc tag.
You might want to read something about escape velocity.
If you had enough air pressure up there for the prop to work against, you could go higher in your Cessna, but you would never go fast enough to keep from falling back to earth once you ran out of gas...
If you could get your Cessna up to a bit over Mach 34 before running out of fuel, you would be going fast enough to keep going up and not fall back.
There are a number of reasons why a Cessna would be a poor choice of vehicle for the attempt, though, even if you happened have a few dozen JATO bottles to strap onto it... (Flying apart before it reached Mach 1, for one...)
That Piper Cub needs air to function, and so do you.
The Piper Cub engine breathes air... once you go high enough, it starts coughing and wheezing just like those climbers going up Mt Everest.
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.
...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 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!
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.