Glenn (and Popular Mechanics) confuse the terms. As is pointed out in the article, rocket packs aren’t “jet” packs.

Remember the rules? If you want to cruise in the atmosphere, use an air breather. A rocket belt sounds cool, but it really makes no sense for this application. Rockets are for accelerating, and getting out of the atmosphere as soon as possible (or for traveling in space, if you’ve already done that). They’re not for tooling around near the ground, or for atmospheric transportation (rocket races being an exception, because it helps push the technology, and sounds cool). A true jet pack, though, would be actually cool, as opposed to merely sounding (and looking, when you see a pro do it at a show, for a minute or so) cool.

A quote from The English Patient, that I happen to be watching tonight. “You can’t explore from the air, Maddox. If you could explore from the air, life would be very simple.”

Charlie Stross isn’t very sanguine about the prospects for space settlement. My main criticism of his argument is that it seems to assume that all materials will come from earth, and that there are no resources available in space. When he writes, for instance:

Optimistic projects suggest that it should be possible, with the low cost rockets currently under development, to maintain a Lunar presence for a transportation cost of roughly $15,000 per kilogram. Some extreme projections suggest that if the cost can be cut to roughly triple the cost of fuel and oxidizer (meaning, the spacecraft concerned will be both largely reusable and very cheap) then we might even get as low as $165/kilogram to the lunar surface. At that price, sending a 100Kg astronaut to Moon Base One looks as if it ought to cost not much more than a first-class return air fare from the UK to New Zealand … except that such a price estimate is hogwash. We primates have certain failure modes, and one of them that must not be underestimated is our tendency to irreversibly malfunction when exposed to climactic extremes of temperature, pressure, and partial pressure of oxygen. While the amount of oxygen, water, and food a human consumes per day doesn’t sound all that serious

Who watches the watchmen on software testing? SpaceX’s control issue might have been found with better testing, but the test case writer didn’t start with a big enough perturbation for the problem to appear. It’s also not clear that the tester software is sufficiently good to tease out problems with the control software. That’s especially true if the same people are writing the control software and the tester software.

The rest of the entry reads like technobabble from a movie like Failsafe. Nevertheless, this is the $64 billion question that can make SpaceX another of Musk’s successes or ground his Mars colonization plans altogether.

Continue reading Software Testing Hard →

Jesse Londin has a pretty good roundup of links. It’s like another space carnival.

Instapundit links to this story on the successful scramjet test Down Under, which (as usual) overhypes the application:

Butler said they could also slash the cost of sending satellites into space, because their potential payload was much larger than a rocket carrying its own fuel.

Even ignoring the fact (probably attributable to an ignorant reporter) that scramjets still have to carry their own “fuel” (it’s the oxidizer that they can leave at home), he shouldn’t buy it. The laws of physics haven’t changed in the three years since I wrote this piece debunking claims that this would revolutionize space lift:

Proponents claim that by allowing airbreathing up to high Mach numbers, there is no need to take along as much oxygen for the rocket engines, because they can gather it for “free.” This argument assumes that space transportation is expensive because propellants are, but those aren’t the cost driver. If they were, space would already be affordable, because liquid oxygen is actually about as cheap as milk. Propellant costs are such a tiny fraction of launch costs that they’re down in the noise. If we ever get to the point where they become a real issue (as they are for airlines), we’ll have solved the problem.

Their argument also fails on the grounds that collecting oxygen isn’t really “free.” As the old joke goes, there’s no free launch.

If your space transport were to be single stage, you’d now need three propulsion systems — conventional jet, scramjet, and rocket for when you left the atmosphere (which you must do by definition to go into space). It may be possible to have a scramjet lower stage and a rocket upper stage, but the bottom line is that time spent in the atmosphere (necessary to utilize the scramjet) is time spent fighting drag, defeating the purpose. Rockets want to spend as little time as possible in the atmosphere, and carrying two other kinds of engines along and spending enough time in the air to utilize them, just to save on a propellant as cheap as oxygen, just doesn’t make design sense.

In addition, a scramjet engine is designed to operate at a specific vehicle speed, and has poor performance in “off design” conditions, rendering it a poor propulsion choice for an accelerating vehicle.

It’s been said that there are three basic rules to aerospace vehicle design, that many designers continue to forget to their peril:

1. If you want to cruise, use an airbreather.
2. If you want to turn, use a wing.
3. If you want to accelerate, use a rocket.

Even with all of the improvements in jet engines over the years, you can’t beat a rocket engine for thrust/weight ratio, and it doesn’t care much how fast the vehicle is going. Chasing after solutions-looking-for-problems like this distracts us from solving the real problem–getting enough market and enough activity to get operational economies of scale, the lack of which is the real cause of the high cost of space access. And the near-term solution to that problem, despite the class-warfare whines of Eurocrats, is commercial space travel.

[Update]

I should probably add my usual disclaimer (as I did in the TCSDaily piece). I’m not saying that scramjets aren’t useful, or that they shouldn’t be researched and developed. The military definitely needs them for atmospheric cruise applications. I’m just saying that space launch will probably not be one of their applications any time soon, and they’re irrelevant to reducing launch costs in the near term (i.e, over the next two or three decades).

[Afternoon update]

One more thought. I’m not completely down on air breathers in general. I do think that concepts for collecting oxygen in the atmosphere are interesting, if it allows you to get the gross takeoff weight of a vehicle down to the point at which it can take off from a runway. It would be nice to have a system that still had LOX tanks, but took off with them empty, and then collected and separated the air (subsonically) until they were full. At that point, it could rocket to orbit. Andrews Aerospace is looking at a concept like this. But that’s not a scramjet, and scramjet technology doesn’t help with it.

[Update late afternoon]

Well, as usually happens in these theological discussions about technical methods of getting to orbit, some of the comments would indicate that I’m a heretic.

I haven’t read SpaceX’s post mortem on their second Falcon 1 flight yet, but Jon Goff has.

It’s an interesting example of a complex system failure, in which a small problem in a complex, highly-coupled system can spiral out of control. As to the question of why put in slosh baffles when the problem wouldn’t have happened with the right software, it’s belt and suspenders. Even with the software problem, slosh baffles may have saved the day, and the additional weight is probably worth the increase in robustness of the system.

Then again, maybe they just added them before they figured out what had really happened…

Of course, the real lesson for SpaceX (and despite the long history of such things, people often have to learn the hard way) is that good configuration management is critical to success.

Gene Kranz has an editorial up decrying the “gap.” Can anyone tell me what’s missing from this piece? Anyone? Anyone? Bueller?

Here’s a hint, from the last two paragraphs:

Shifts in the world

Pamela Gay hosts it this week, with an emphasis (but not exclusively) on space science.

I just got the following (registration required) from an aviation mailing list. There’s certainly nothing hard to believe about it (though it would also be possible to do the same thing as a parody, I suppose).

The European Union’s industry commissioner on Thursday blasted companies’ plans to offer space flights to tourists, calling them a gimmick for the
privileged elite.

“It’s only for the super rich, which is against my social convictions,” European Commission Vice President Guenter Verheugen said.

EADS Astrium, the space division of the European aerospace consortium, said this week it planned to build a craft that would be able to carry a handful of tourists on brief forays outside the earth’s atmosphere from 2012.

Other groups are considering similar ventures including British entrepreneur Richard Branson, whose Virgin Galactic service expects to make its first commercial flight next year.

The EADS aircraft, about the size of an executive jet, would be able to carry four passengers around 100 kilometres from the earth, where they would be able to experience about three minutes of weightlessness and see the curve of the earth.

At a price of EUR150,000 to EUR200,000 euros ($200,000-$265,000), the experience would be reserved for a small number of rich sensation-seekers, although as many as 15,000 passengers a year are expected to be ready to pay for a trip by 2020, according to consultants Futron.

That would represent a considerable expansion from the tiny number of truly rich adventurers so far who have been willing to pay as much as USD$20 million for a place on a Russian Soyuz rocket to see space.

Verheugen, a German center-left politician who holds the industry and enterprise portfolio within the EU Commission, said the new space race left him uneasy.

“I have strong reservations,” he said. “It will always be a very privileged type of tourism.”

EADS Astrium expects to build about five craft a year and thinks it can capture about 30 percent of the market.

The EADS Astrium project will be mainly privately financed, and Astrium will not operate flights itself, but Verheugen made it clear that he did not believe it deserved assistance from governments or the European Union.

“I have no sympathy for this. It deserves no support.”

Verheugen was speaking at the margins of an awards ceremony to commend EADS’s Airbus unit for its efforts to reduce carbon emissions from its aircraft, a coincidence that underlined another potential concern about space tourism.

At the same ceremony, Louis Gallois, head of Airbus and co-head of EADS, declined to answer a question on the apparent paradox of a company trying to cut emissions in one area while investing in a project to blast rich travellers into space.

Airbus recently announced a 25 percent increase in its EUR350 million budget to research the cutting of emissions, a figure dwarfed by the estimated EUR1 billion in expected development costs for the new spacecraft.

Emphasis mine. With morons like this in charge of “Industry and Enterprise” in the EU, is it any wonder the place is such a stagnant economic mess?

This is so stupid and stereotypical, that one hardly even knows where to begin, and the arguments have been made (many times) before.

Yes, of course, at first, only the “privileged” will use the service. That’s how one gets the price to drop so that the “non-privileged” can eventually afford it. But the point isn’t (or shouldn’t be) about subsidizing rides for the rich (assuming that subsidies are involved at all–this economic illiterate seems to think that even private funds shouldn’t be spent on it–he knows better how to spend other peoples’ money than they do, of course). The point is that by developing these kinds of vehicles, we can ultimately reduce the costs of getting into space for everybody and everything, including many things that presumably even our socialist bureaucrat might find to his liking, such as remote sensing satellites for environmental monitoring, etc.

As for the environmental issues, the amount of environmental damage caused by rocket planes, even if they burn hydrocarbons, is spitting in a hurricane compared to commercial and other jet traffic at any reasonable expected flight rate in the near future. In the far future, they may go to LOX/hydrogen, which will of course pollute the atmosphere with that deadly dihydrogen monoxide, which many think should be banned completely. But again, when it comes to the environmental effects, one has to look at the benefits as well as the costs. Most sensible environmentalists should want us to move as much polluting industry off the planet as soon as possible, and the only way to make this happen is to reduce costs of space access, which is only likely to happen from the competitive environment and economies of scale that a space travel industry will provide.

But then, “sensible” is not the first adjective that comes to mind in reference to people like Herr Verheugen. In fact, it’s not even on the list. I have no fear of the EU as long as his type remain in charge.