"My "April Fools Day in India" post -

http://www.habitablezone.com/space/messages/12279.html

was a little emotional, but I honestly would like to know if it really is hare-brained, or just looks that way. If there is a way to liquefy 22 tons of oxygen while flying at Mach 8, I'd love to hear of it. Or "just" to cruise at Mach 8 for an hour... "

Harebrained it is (I thought it was hair brain- but the dictionary is on your side, in any case, the idea is silly if they are serious about getting into space).
A couple of years ago I posted an idea which involved using the atmosphere's oxygen. The idea was to have a reusable space vehicle which never landed on Earth, but went from orbit to high altitude then back to orbit. I was thinking you could gain oxygen coming down, then fuel and load cargo/passengers mid flight. But even I was not thinking of it as way which could be used right now- needed more demand and more infrastructure in space. And I think I later discarded the idea of oxygen because it simply added too much complexity (just bring up the oxygen with fuel). BUT one advantage of getting oxygen coming down is that it would cost a lot of energy to collect oxygen and you need to shed lots of energy de-orbiting, so putting these together seemed logical.

Now the idea of using turbine jet engine instead of rockets for the first stage of getting into orbit has some merit, I think. One problem is getting a big enough "mothership" (airplane) which can carry a big enough spaceplane. There are lots of different ideas which revolve around the idea of using the more efficent jet engine to lift the rocket fuel "part way up". Pegusus is launched this way. Boeing was recently toying with idea of launching a larger version of pegusus but using LH&LOX rocket and having space vehicle perched on top of mothership. Russians have also been promoting idea- they have biggest usable mothership available. And we also have the idea of towing a space vehicle and refueling mid-flight- can't remember the name.
All of these type of ideas should be seen as an "assisted launch"- adding to the rocket's performance. Also I believe this assisted launch would be limited to "around" the speed of sound. So in this light, using a MagLev is similar type idea- but even simplier cause you aren't even leaving the ground- you should be able to carry significantly bigger rockets and cheaper.

Btw, this line of thinking kinda sorta led me to the idea of my "pipelauncher"- a even further devolution- planes, rail, and finally boat:)
-gb