Go for it, Burt!

Which 3? Maybe you're considering the Marines part of the Navy? Or maybe you're leaving out the Army since they haven't had any astronauts (that I'm aware of, besides Roger Healy :)

(I usually hear it as 4 branches.)

Which ones?

Doug

Hello: could someone explain how Burts plane can go into low earth orbit, without having to achieve the escape velocity of the earth? When would the escape velocity take effect if he had wanted to go higher? thank you

It didn't go into orbit, just went up to "space" altitude and back down. He would have needed more velocity to reach low earth orbit. (Compare the Redstone and Atlas flights, both launching similar Mercury capsules...)

-dave w

without having to achieve the escape velocity of the earth? When

The Department of Defense is divided in to three military branches; Army, Navy, and USAF. The Marine Corps is part of the Navy.

The US Army has Astronaut, Senior Astronaut, and Master Astronaut wings, but I don't believe any of these have ever been awarded.

He didn't go -into- orbit.

Joel. phx

>

Escape velocity is needed to move beyond Earth orbit; the Moon or Mars, for example. Orbital velocity is needed to achieve Earth Orbit. Space Ship One is not capable of either.

There are 4 US Military Astronaut Wings, Army, Navy, Air Force and Marines. I haven't researched it, but I'm pretty sure all have been awarded.

Mario Perdue NAR #22012 Sr. L2 for email drop the planet

"X-ray-Delta-One, this is Mission Control, two-one-five-six, transmission concluded."

The Marines issue their own wings?

What Army astronaut are you thinking of?

STS-58 William McArthur, Col, US Army STS-101 Jeffrey Williams, Lt Col, US Army STS-105 Patrick Forrester, Col, US Army

Mario Perdue NAR #22012 Sr. L2 for email drop the planet

"X-ray-Delta-One, this is Mission Control, two-one-five-six, transmission concluded."

Hi Clifton! Spaceship One didn't go into orbit, it merely went high enough to reach space. (Same with Alan Sheppard's first flight in Mercury.) To reach low orbit, they would have needed to go much faster, somewhere around 17,000 mph if I remember correctly. Escape velocity is even faster, and is the speed required to leave Earth orbit.

Picture a porpoise or dolphin jumping out of water. Just enough speed to break free for an instant, but they fall back into their atmosphere (water). That's what space ship one accomplished. He made it to space, but was still being strongly influenced by gravity and it pulled him back down.

steve

Dumb question time... but how would 'escape velocity' even apply to Spaceship One (which 'launched' from 50,000 ft)? I mean, I thought escape velocity was the initial velocity (ignoring drag) needed when taking off from the surface of the Earth, without any additional thrust after escape velocity is achieved. On the other hand, you could escape Earth's gravity as slowly as you like, as long as you can continue to apply just enough thrust to more than counteract gravity. Right?

I just saw another mention of the wings that said Melvill will receive "the first set of Federal Aviation Administration (FAA)-issued commercial astronaut wings."

It's in one of the articles at space.com

Mario Perdue NAR #22012 Sr. L2 for email drop the planet

"X-ray-Delta-One, this is Mission Control, two-one-five-six, transmission concluded."

"Escape velocity" is the speed needed to escape Earth orbit (somewhere around

25,000 mph, if I remember correctly). Where and how you launch is irrelevant. Being dropped from a plane at 50,000 feet simply means that the rocket won't have to work as hard or burn as much fuel as it would from a standing start on the ground.

But... Let's say I am gaining altitude at a constant rate of 1000 mph (far less than the Earth's escape velocity), and continue to do so. Eventually, I will escape the Earth, the solar system, and the galaxy, won't I? And if not, how come?

Sure. You will have to have some constant thrust to oppose the gravitational forces acting on you so as to maintain your constant velocity (relative, I guess, to the point you are heading to), but you would eventually get where you want to go.

You were right the first time. Escape velocity is the initial velocity needed to escape the earths gravitational field (from the surface) without any additional energy input.

Mick wrote:

There are two velocities to consider. The radial velocity is the speed at which you are moving away from the earth. Sort of like taking an elevator up. Motion is perpendicular to the surface of the earth.

The second velocity is the speed encountered while going around the earth in circles - ie, orbits. Motion is parallel to the surface of the earth.

When folks speak of orbital and escape velocities, in both case they're talking about the circle velocity. At ~18000 mph, the centrifugal force outward is about the same as the gravitational force inward, thereby keeping the object in orbit. At higher altitudes, the force of gravity is reduced, so less speed is needed, but in general, 18000mph is the magic number for orbital velocity.

Escape velocity is the orbital speed required to build up enough centrifugal force to break the bonds of gravity and fling yourself into space AND have enough momentum that the force of the earth's gravity will diminsh sooner than you lose your momentum. Ie, you won't slow and get pulled back to earth.

For the elevator approach, escape velocity could be 1mph. But the key is that orders of magnitude more impulse would be required to do it this way than using the circular method. If you could build a rocket many times bigger than a Sat V, then you might be able to do it this way. But your thrust level must be greater than the force of gravity the whole way.

Whereas with the circular method, as you gain speed, you gain centrifugal force which is cancelling the force of gravity. So you don't need nearly as much impulse, and hence a smaller rocket will suffice.

Another consideration is drag. As the altitude increases, there is less drag from the thinner air. At high enough altitudes, the drag is negligible so once an object is accelerated to orbital velocity and reaches a high enough altitude, it can coast forever thereby staying in orbit.

So the key here is reaching a high enough altitude and then having enough speed (momentum) left to stay there.

HTH.

Doug