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It fell to the bottom.

Thank you, Midoshi. I will certainly review your sources! Thanks ever so much for providing them!

I don't see anybody counting the extra assist from the low latitudes at Kourou as one more stage. If it's on the ground, separate from the vessel going to orbit, I don't see why it should be counted.

You're just fudging semantics because you apparently don't want to accept it as a SSTO.

And that's why I'm in Clinton's corner for this fight.

No, its claim to superiority is its immense thrust, which works just as well in space as in atmosphere, except in space the pollution is much less dangerous. If you're going to use it where its negatives do the least damage, go ahead and bother.

I do not believe we can tolerate that much CO2.

Here's from Wikipedia:

http://en.wikipedia.org/wiki/Carbon_dioxide#Toxicity

"It is dangerous when inhaled in high concentrations (greater than 5% by volume, or 50,000 ppm). The current threshold limit value (TLV) or maximum level that is considered safe for healthy adults for an eight-hour work day is 0.5% (5,000 ppm). The maximum safe level for infants, children, the elderly and individuals with cardio-pulmonary health issues is significantly less.

"Concentrations higher than 1,000 ppm (0.1%) will cause discomfort in more than 20% of occupants, and the discomfort will increase with increasing CO2 concentration. The discomfort will be caused by various gases coming from human respiration and perspiration, and not by CO2 itself. At 2,000 ppm (0.2%) the majority of occupants will feel a significant degree of discomfort, and many will develop nausea and headaches.

Also remember that O2 levels have to be kept below 30% or so to reduce flammability.

Given those two factors, we'd still need 70% of the atmosphere from some other source.

I think Orion would probably be feasible as interplanetary transportation but never landing. Constructed in orbit, used to ferry back and forth between, say, Earth and Titan, but at those ends it would just transfer its cargo to other ascent/descent mechanisms in orbit rather than landing. It can dock with a space elevator and send cargo down via it, or it can have smaller shuttlecraft in bay to take things up and down, but an Orion should never get into a planet's atmosphere, IMO.

I'd definitely like to see some research done into an Orion-based heavy cargo transport with the mission to bring a bar of nitrogen from Venus to Moon or Mars.

Also, if the buffer gas atomic mass is much higher than oxygen, then won't it displace the oxygen, like a heavier liquid sinks to the bottom of the glass? Thus completely depriving the surface of oxygen.

Nitrogen is roughly the same as oxygen, so it doesn't displace the oxygen and the two mix at the surface. But if we had some really heavy buffer gas, it would create pressure, sure, but it would also separate all the oxygen away from the surface.

Depends on how big a shipyard. If it takes 1 cubic meter, sure. If it takes a million cubic meters, no. How many cubic meters does a shipyard need? Answer that, and you have the answer to your question.

A gas expansion cannon strikes me as wasteful (though I haven't done the math to verify), but a mass driver certainly has been considered a valid idea at least as far back as that Clarke or Heinlein book about the Moon.

I was actually just doing mass driver calculations yesterday (hence why I mentioned the idea in the SSTO thread) and I'd say there's definitely promise in the idea as a *supplement* to launch, but putting something in LEO or GEO *just* by mass driver would require too long tracks to be built in our lifetimes. However, we could definitely build launch tracks that'd add 1000-3000 m/s to launch which would help quite a bit.

Lemme go get my calculations and I'll get right back to you.

One of the things I seem to recall is that using a linear launch track will be able to provide a roughly 4x better exit velocity for the projectile than a circular (infinite length) launch ring. This is because a circular mass driver will exert pretty significant centrifugal forces. Given the same amount of physical construction materials (1km diameter launch ring = 3.14km of constructed length versus a 3.14km linear track), if you are limited by, say, 10g -- then in the launch ring where you'll be able to get n exit velocity, in a linear track you'll be able to get 4n.

I'll need to verify that with some more calculations but that's what I seem to recall from yesterday's math.

Edit: Okay, back with some math.

The factor of difference is 3.544908. A linear accelerator will be able to give you 3.5x better exit velocity than a circular one, assuming the same amount of construction materials and the same g-force tolerance in both designs.

In a launch ring, you are limited by a = v^2/r. That's the centrifugal acceleration, the g-force you're experiencing: v^2/r

Taking as an example, a ring that is 1000m in radius (total 2000*pi construction length), and a g-force tolerance of 10g (98.1 m/s/s).

v = (ar)^0.5 = 313 m/s

At the point when you're going 313 m/s, you will feel a 10g centrifugal acceleration. Now, a launch ring, with an infinitely long track, *will* be able to accelerate you for infinitely long, to ten times escape velocity if need be, but the g-forces will only get more intense the faster you're going, so you'll be dead long before you reach escape velocity.

A linear track, comparatively, is limited by its length (since it doesn't have infinite room to accelerate you in) and again, your g-force tolerance.

Taking again the same 10g g-force tolerance, and the same amount of construction materials (2000*pi length) we'll have an acceleration track of some 6300 meters, and 10 gs to pull in it. In a straight line track, we're limited by:

x = 0.5at^2
t = (2x/a)^0.5
x = 6283m
a = 98.1 m/s/s
t = 11.31802 s

It'll take a little over 11 seconds to travel that 6+ kilometers at 10g, and when you exit the track, you'll be traveling at:

v = at = 1110.298 m/s

v (linear track) / v (launch ring) = 1110/313 = approx. 3.5

So you can get 3.5 times the speed off a linear track. If you have the materials and money to build 6km of acceleration track, it makes more sense to build it straight than in a circle.

Incidentally, a 63km launch track at 10g would take 36 seconds from end to end, and you would exit at a velocity of 3511 m/s -- nearly half of what you need to reach ISS. I think ~60km is just about the top end of what might be achievable in our lifetimes. The smaller scales, a few kilometers in length and giving ~500-1000 m/s boost should *definitely* be achievable.

A 630km launch track at 10g would take 113 seconds (under two minutes) to travel, and you would exit at a velocity of 11,102 m/s. That's the kind of megaengineering scale you'd need in order to not have any significant rocket boosters on the projectile itself at all, just minor thrusters for precision.

So at dozens of km of launch track, you can get half orbital velocity...but you'll need *hundreds* of km to get to actual escape velocity. It's a factor of ten or so.

The "Eat like a Martian" thread (the link is right there in the post where I discussed the matter).

Either or. General space colony rather than a moon or planet colony. You can discuss heliocentric or geocentric ones, either works.

So...if they could be used to build a shipyard...then couldn't they also be used to build ships? Making them, by definition, a shipyard?

So, in essence, you want to build the shipyard out of Bigelow modules. Okay, I suppose there's nothing in principle preventing that.