Think of it as a very long term student loan.

Peak Oil may be a ways off, but we've definitely hit Peak Buzzword.

Wow, that was the most condescending post ever. Not only am I well aware of how an endowment is operated -- this is a regular topic of faculty meetings, for god's sake -- my earlier post did assume only investment income was spent. A 3.5% return on Harvard's 1.7 million per student endowment would give an annual income of $60,000, which is equal to Harvard's tuition plus room and board. Historical rates of return for the last couple centuries are significantly higher than 3.5%, which would likely allow Harvard to keep up with inflation in perpetuity.

And by the way, I teach at a liberal arts college, but I teach physics. A liberal arts education is not the opposite of math and science: it's about creating well-rounded students who're strong in both humanities and the sciences. Since you've proven yourself incapable of either understanding a written argument or doing math, you clearly didn't get one.

So crawl on back to your troll cave, you've got nothing to contribute to this discussion.

... and that's great news, for a couple hundred brilliant but poor kids. But these three schools can only do so much. Meanwhile, millions of other talented and deserving students can't afford to attend college at all, or can only attend underfunded schools with decaying equipment and underpaid professors teaching classes of 500.

You'd think, but Texas A&M is in the top ten. Probably because a fair number of Texas oilmen are football fans.

If you went to a Harvard, a Stanford, an MIT or a Texas A&M, and you happen to end up with more money than you know what to do with, you might be inclined to give a big pile of it to the university that got you started. And while that's a noble sentiment, you shouldn't. These places will continue turning out talented graduates no matter how much money you give them: you should give your money to a less-well-endowed institution, so that a larger number of students can get the same educational opportunity you had. Maybe your spouse went to a small liberal arts college. Maybe there's a place right down the road from your mansion that could use your help. But MIT and Stanford don't need your money, and they won't do much good with it.

A bit of data: Harvard's endowment amounts to $1.7 million per student. With a reasonable return on endowment investment, hey could quite literally abolish tuition forever if they wanted to. Just across the river is Boston University, a really excellent institution with a strong research focus and really great graduates, ranked #42 by US News. Its endowment per student is 1/25th of Harvard's.

Donating money toward improving education is a worthy goal, but don't get sentimental. Put the money where it'll do the most good for the most people.

(Full disclosure: I'm a professor at a liberal arts college whose endowment per student is mediocre at best.)

I don't do this for a living, so don't take me too seriously. The smaller you make the first stage, the more work must be done by the second stage, which means *it* must be bigger, increasing the useless mass that makes it into orbit. Also, the smaller the first stage is, the less it costs, so it's less valuable to recover...

You're absolutely right that there's an optimization problem to be solved here, and that a rocket optimized for first stage recovery might look very different from a stock Ariane 5 with wings on the bottom. But this rocket *does* look like a stock Ariane 5 with wings on the bottom, which makes me worry that they haven't done the math.

But aviation has gone backwards. When I was young, anyone with a few thousand dollars to spare could fly across the Atlantic in comfort at twice the speed of sound, and military pilots in a close approximation to space suits would be flying above them at nearly twice that speed.

What's progress? Is progress defined in terms of how fast we can get a handful of millionaires from New York to Paris, or in terms of turning an ocean into an insignificant obstacle for average citizen of the developed world? Today's airfares are about a third (in constant dollars) of what they were when you were young, and there are six times as many people flying. Turns out that the ability to fly to Paris at Mach 2 was a pointless waste of effort and money. What that changed the world was the ability to get there for less than two weeks' wages.

I do not think you know what a turbofan is based on what you stated.

The article mentions "turbofans" but the video at the bottom of the link clearly shows external propellers (i.e., a turboprop). It's the article that's confused, not the grandparent poster.

It does - but turbofans and horizontal flight with lifting surfaces is far more efficient than attempting to land vertically using a rocket engine, and we have 110 years of experience landing aircraft horizontally, or if you want to combine total experience, probably approaching on a million combined "man years" of experience landing aircraft

SpaceX has an actual flying reuse system that might or might not work. TFA is discussing a back-of-envelope concept that hasn't even gotten to the detailed engineering yet, much less flown. You might be right, landing with wings might turn out to be a better idea. But there's tens of millions of dollars of blueprints and welded aluminum to go before we can make an apples-to-apples comparison between them. In the meantime, SpaceX will either succeed or fail. There's no point in saying either design is "better" before that.

That's my point. Progress happens in all fields of engineering, but computer engineering happens at such a radically different tempo that it's not a useful comparison.

Now where are the vertical-takeoff hypersonic airliners I used to see on TV as a kid?

Space, as it turns out, is really hard. There are two basic kinds of techological miracle: working with microscopic quantities of matter and energy, and working with vast amounts. Science fiction authors of the '60s assumed that mega-scale engineering would continue at the incredible pace set during the 20th century, but it turns out we were just getting to the hard part. But they drastically underestimated what we'd be able to do with micro-scale engineering.

Good examples, though these props will be operating at *much* higher speeds and stresses than a motor glider, and the Osprey's props don't unfold in flight. Well they're not supposed to anyway.

This is only a first stage. So, not "most of the way to orbit."

Well, sorta. This flyback proposal is based on an Ariane 5 style rocket, which has solid boosters which drop off early and an oversized LH2-LOX "main stage". Whether you call the main stage a first or second stage is semantics: the important point is that it goes all the way into space, and most of the way into orbit. See this launch of Ariane 5, where main stage separation happens at a velocity of 7 km/s (out of about 8 km/s needed to reach orbit.)

Ask the guys who designed the shuttle. Shuttle did that, too. ;)

Oh sure, it's possible, but I think you'll agree that the ideal number of holes in your heat shield is zero.

Aircraft technology isn't stagnant by any means: a modern 777-ER can carry the same number of passengers 50% farther for a third less fuel than the original 747-100. But that just proves your point, that breathless Moore's Law comparisons are moronic when talking about airplanes, cars, rockets, and bridges.

This has the look of a paper concept that nobody's put any engineering work into yet. Some possibly show-stopping engineering challenges:

1) The air-breathing engines are dead weight dragged most of the way to orbit. And turboprops and turbofans are pretty damned heavy compared to rocket engines: for many applications, the weight of fuel and tankage is so much greater than the engines that engine mass is irrelevant, but that's not the case here. SpaceX's design makes use of engines that need to go to space anyway.

2) Looking at the videos, the design relies on folding propellers that deploy in flight. This is ... not an easy thing to do. I'm not aware of any aircraft larger than a duck that uses this technique, even on carrier-based aircraft where space is at a premium.

3) While rocket engines are pretty lightweight compared to turbine engines, it's still a lot of weight to fly back home. The video shows a flyback aircraft with very short stubby wings. In addition, the wings can't be asymmetric lifting airfoils or they'd push the rocket sideways during lauch: the have to be flat boards. The return vehicle is likely to have a very high stall speed, making landing a challenge.

4) The video shows no details on how this propulsion module is attached to the fuel tank above it. This is difficult: enormous fuel and oxidizer pipes need to pass through the nose of the propulsion module, along with gigantic clamps attaching it to the fuel tank... but this surface is exposed to re-entry heating on the flight back. How do you route plumbing and avionics through your heat shield?

Being able to remotely transmit commands in a new general-purpose programming language to the server that stores your irreplaceable data? What could possibly go wrong?

Also, how do you say "Robert'); DROP TABLE Students;" in R?