The same could be said of virtually any powered aircraft. The length of time that they can spend 'aloft' is limited by the amount of fuel that they can carry. It's besides the point.

That's the issue; as long you're making enough power to overcome gravity, you can 'stay aloft' at any altitude, and you definitely don't need orbital velocity to do so. Orbital velocity is the speed needed for an unpowered craft to remain in orbit. It has nothing to do with a rocket plane flying around at 100m or 200km. Postulate a rocket plane big enough to hold the required fuel and nothing would stop it from flying up to 200km, maneuvering around 'aloft' for an hour and then flying back down.

I never argued otherwise.

I have to disagree with your statement that ARCA is doing something 'genuinely innovative' by using a balloon for the first stage. The concept is called a 'Rockoon' and was pioneered in the US in 1949 and has been used extensivly by JP Areospace, (among others), a small US company that has been working with balloons and rockets for over 30 years.

http://jpaerospace.com/rockoons.html

What??? Sorry, you need to go back and rethink that statement; it's not even close to true. Can you explain how SpaceShipOne, flying at 'only' Mach 3, was able to go higher than 100km? Thus, not only staying aloft at at 100km, but climbing? Or the X-15, which also flew higher than 100km, and also at significantly less than orbital velocity?

I like how a good authoritative sounding statement, (which happens to be false), got modded +4 informative.

I might be missing a joke somewhere in your post, and appologize if I am, but I'm getting the distinct impression that you're misinformed as to what the hardhack tag is for.

Hint: It involves hacking hardware as opposed to software....

Why all of the unfounded pessimism? Are you people completely unaware of how many rockets we launch into space every year?

Then who the hell designs and builds the rocket engines for the Ariane, or the Atlas, or the Delta, or the Falcon, or any of the half dozen or so other heavy lift rockets in operation or development around the world?

What?? How do you think they refurbish them after the missions if they don't understand them completely? How was Rockwell able to build a new shuttle in the early 90's, including rocket engines, if no one is left? That space division, now owned by Boeing, still designs and builds new rockets. How can that possibly be?

I was surprised (naive, I know) that the link in TFS was not to the X-Prize website, so I went looking for it.

It turns out that deep ocean exploration is only one of several contending future exploration X-Prizes.

Is this an attempt to stack the deck in Cameron's favor by forcing the competition choice through publicity as if it's a forgone conclusion, and meanwhile he has maybe a six month head start on the competition?

You too should read "The Case for Mars". There are many reasons for colonizing Mars, not the least of which is as an offsite backup for humanity.

Other reasons range from the practical; with Mars as source of rare elements not available in sufficient quantities on Earth, to the esoteric, with the new Mars frontier providing the challenge that humanity needs to hone its pioneering edge.

You should read the book "The Case for Mars". It does a really good job about laying out all of the issues and technologies related to establishing a manned presence on Mars.

To summarize one of the points; there is no reason to go to the Moon first as a staging ground for Mars. Quoting from the Wikipedia article:

"In the same chapter, Zubrin decisively denounces and rejects suggestions that the Moon should be used as waypoint to Mars or as a training area. It is ultimately much easier to journey to Mars from low Earth orbit than from the moon and using the latter as a staging point is a pointless diversion of resources. While the Moon may superficially appear a good place to perfect Mars exploration and habitation techniques, the two bodies are radically different. The moon has no atmosphere, no analogous geology and a much greater temperature range and rotational period. Antarctica or desert areas of Earth provide much better training grounds at lesser cost."

What the hell are you talking about? What do you think fuels our continuing huge advancements in science, and well, everything from manufacturing technologies to medicine? Building on pre-existing accomplishments, solutions and ideas, that's what.

When you hear stories talking about how we lost the technology to rebuild the Saturn V rockets that were used last time, it's absurdly shortsighted to interpret that as meaning that humanity can't go to the Moon. We are sending unmanned missions there all the time; the only thing keeping manned mission from returning are other budget priorities.

Yes, we would probably have to relearn some of the manufacturing steps involved if we wanted to recreate the original rocket designs exactly, but why the hell would we want to do that? It's 50 year old technology that we no longer care about. We also can't build giant stone pyramids as well as we used to be able to, but does that stop us from building modern cities?

Take your hands out of your pants and go get an education.

There's been this breakthrough in technology for working in the dark, called floodlights.

On second thought, submersible designers probably don't like the terms breakthrough and flood used in conjunction with their projects.

Everyone is banging their head over trying to hit Mach 10 on the track.

TFS and everyone else is misunderstanding the proposal.

The current idea is for the sled on the track to accelerate a scramjet up to about 600mph, then the scramjet lifts off, flies up to altitude and at about mach 10, releases a rocket which boosts the payload into orbit.

Sled (reusable) on the ground = 1st Stage
Scramjet (reusable) in the atmosphere = 2nd Stage
Booster Rocket in space = 3rd Stage

All extensions of more or less current technology.

How does something going 7 km/sec catch something going zero?

Colliding, I can see. Gently catching and accelerating up to the same speed, I don't see.