I’m trying to figure out just how much extra mass can be launched with the boost given by the airplane, compared to if the rocket was conventionally launched from a standstill on the ground.  Here’s what I’ve come up with:

According to the Stratolaunch article on gizmag.com, the rocket weighs 500,000 pounds when dropped from the airplane and ultimately gets 13,500 pounds into low earth orbit.  The ratio of those two numbers is 37:1.  So, for each pound launched into LEO, there’s 37 pounds of rocket at initial drop.  OK.

Is 37:1 a particularly high or low ratio?  I have no idea.  So I keep digging and guessing…:

Over at spacex.com, there are vital stats for their similar-technology Falcon 9 rocket.  It weighs 735,000 pounds at launch (from the ground) and ultimately gets 23,000 pounds to LEO, or a ratio of 31:1.

As for the smaller Falcon 1e rocket, it weighs 78,000 pounds at launch and ultimately gets 1,000 pounds into orbit, or a a ratio of 78:1.

So:
o Falcon 1e: 1,000lb at 78:1
o Falcon 8: 23,000lb at 31:1
o Stratolaunch: 13,500lb at 37:1

So.  According to these numbers, launching from the airplane, instead of from the ground, doesn’t make much of a difference in terms of how much mass is launched per pound (~= per $’s worth) of rocket.

Ergo, as was pontificated above, the real point of doing it this way must be because of practical reasons like
o fewer launches scrubbed due to weather
o you can launch into any sort of orbit
o you can launch comfortably out over the very remote ocean

Hm.  Well.  If anyone can help support or trash my line of reasoning here, I’d very much appreciate it.

And here’s the thing- I’m in a pretty much perpetual fury about the American distribution of wealth, and dereliction of public services, and the massive moral and market failures in our dealing with the very poor, and the environment, etc., etc. I’m the guy in the corner furiously working the white board and combing the literature for the neat fixes that would make the current political culture lose it. The boston.com Big Picture on homelessness today nearly made me cry. It’s just that I don’t understand the fixation- public and commercial spaceflight is such a small, innocuous, variously fascinating and useful bit of infrastructure, but like a moth to flame, you mention rockets and someone will lob in a zero-sum guilt bomb about the poor, as though in the world of trillion-dollar tax loopholes, someone starting up some medium-cap business like this was relevant to the discussion.

Rockets, why you no fix homelessness?

How many escape pods did the Mayflower have, does anyone recall?

Sure, but it’s the fact that so many get so much more excited about the former than the latter, and that the former seems so much more possible than the latter (while the latter is actually much more readily achievable), that’s so galling. Desparing, even. 

Hmm. And someone rich–let’s say, Lady Gaga–can say, “No, I’m not ‘rich.’ Look at Bill Gates. Now THAT’S someone who’s rich!”

[edit to add:]

Do you really think that if we suddenly cut all funding for space exploration that money would suddenly go toward helping poor people?

No, I don’t think in those zero-sum terms. I do think that Gil Scott-Heron made an awesomely astute and enduring observation, though, about the clothes-less state of the emperor, and about race and economics more specifically. His point applies to just about any large-scale expenditure with such abstract, long-term goals toward the betterment of humanity, while certain readily identifiable blocks of humanity continue to languish in egregious and relatively fixable neglect.

[edit to add:]

Do you really think that if we suddenly cut all funding for space exploration that money would suddenly go toward helping poor people? You’re right to suggest our national priorities are totally screwed up, but the problem isn’t that going to space is a bad thing. The problem is that we’re neglecting to do a lot of GOOD things. There’s no reason we couldn’t rebuild inner cities and develop low-cost space launch systems.

The decades-long, multiple-leveled neglect of urban America constitutes a set of human causes. To wash one’s hands of the resultant problems as hopelessly unfixable is, at best, to ignore those human causes, and to ignore as well the ability society does have to fix them.

Imagine if someone instead spent $200 million on rebuilding an inner city or two.

We spend untold billions of taxpayer dollars on inner city problems, the problem is that most of it goes to the War on Drugs. At least space exploration doesn’t make the lives of poor people appreciably worse.

If I remember correctly, at least one of the proposed designs in the program which eventually led to the space shuttle used a runway-launched carrier which delivered a smaller vehicle to the edge of the atmosphere for orbital insertion using its own engines.  I always liked that design, and was sad to see it replaced by the final shuttle launch design.  While thundering into orbit with rockets is certainly spectacular, it can also fail in spectacular ways.  Taxiing down a runway, climbing smoothly to altitude (with the option to just _land_ again if things aren’t going well) and dropping the payload there has always felt much more sane to me. 

I really hope they can pull this off.  It would be amazing.

http://www.youtube.com/watch?v=PtBy_ppG4hY