passenger space travel

[pilgrimflyte]

It seems as though (as usual) the private sector is well ahead of the government. After reading about companies developing space planes, and passenger space travel as early as 2007; the technology exists to go beyond that of the space shuttle. It will be good to see the day when those fragile tiles that protect the shuttle will no longer have to be necessary on future space planes. They are way too fragile, and too easily damaged. It is hard to think that FOAM could have hit the tiles so hard as to have caused some to fall off, and cause the death of seven good people. There is, and will always be risks for space travel. It will just be good to see takeoffs from runways, travel, perform their missions, and return more safely than now.

 

[najab]

First off, welcome to Uplink.<br /><br />Second, the foam didn't knock tiles off the Shuttle, it hit the wing leading-edge and damaged the RCC (reinforced Carbon-Carbon) panels that make up the front of the wing.<br /><br />Thirdly, no private individual or corporation has yet demonstrated or tested a reusable vehicle capable of reaching orbit. The flights that will be offered by Virgin Galactic (and others?) will be sub-orbital. Basically they go straight up and straight back down. In order to orbit they will need to add 17,000mph or so of horizontal velocity!

 

[mars_or_die]

SpaceShip One's second X-Prize flight reached an altitude of 69.xxx miles. If I am not mistaken can't a stable Low-Earth-Orbit be maintained at 70 miles?

 

[najab]

><i>If I am not mistaken can't a stable Low-Earth-Orbit be maintained at 70 miles?</i><p>A 70 mile high orbit is stable in terms of tens of hours. But that's not the point - it doesn't matter how high you are, it is all about <b>how fast</b> you're going. It's a common misconception that spacecraft climb to orbit, in reality they climb to get out of the atmosphere. (If not for atmospheric drag, you could orbit the Earth at 5 miles - or even inches above the surface.)<p>Thought exercise: We're standing on the Moon (convenient since it has practically no atmosphere). Take a rock, throw it horizontally as hard as you can, it travels some disance and falls to the ground. Now use a slingshot (a really powerful one) and it goes further before it hits the ground. Remember that the Moon is round, so the ground slopes away over the horizon. If you shoot the rock out hard enough for it to go over the horizon, the ground is sloping away as it falls so it goes a <b>lot</b> further.<p>If you throw it hard enough it will fall at the same rate as the ground falls away from it and it'll come back and hit you in the back of your head (Owch!) - in other words it's in orbit.<p>Note that we didn't have to impart <b>any</b> vertical velocity to get it into orbit, in fact if we had thrown it straight up it would just have come right back down and hit us! And that's the problem with SS1 - it doesn't accelerate horizontally, nearly all the acceleration is vertical. It's horizontal velocity at apogee (the peak altitude) is less than 300 mph. To orbit the Earth you need to go at least 17,000mph.<p>I've attached a (very crude) graphic to try and illustrate the concept of <i>accelerating</i> to orbit.</p></p></p></p></p>

 

[najab]

To explain the graphic above - the lines show what happens as you throw the rock harder and harder. The red line is the slowest throw, the blue line is the hardest.

 

[teije]

Just remember to duck in time if you throw along the blue line. <img src="/images/icons/wink.gif" />