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« Risks Of Human Spaceflight | Main | Jerry Springer, Call Your Office »

Wings Versus Capsules

Kind of like Mothra versus Rodan, we have another round of this ongoing theological discussion in progress. Now, "Publius Rex" takes issue with the piece a few days ago by Jeffrey Bell that shredded many of the arguments for a winged Orbital Space Plane.

I discussed the issue then, but my main point remains that, while these are interesting technical arguments, they're ultimately irrelevant to our future in space, because given its current philosophy and the politics of the situation, NASA is unlikely to come up with anything that reduces costs or significantly improves safety. That will come only when we stop looking to NASA for our space transportation needs, and increase funding to the private entities to whom those things actually matter.

Posted by Rand Simberg at July 21, 2003 10:03 AM

Comments

At least, there looks to be some hope for sensible policy discussion in near future:
http://www.spacetoday.net/Summary/1806

"A poll published Sunday by the Houston Chronicle reveals that a majority of Americans want to keep the space shuttle grounded until NASA redefines the goals of the nation's space program. The poll, conducted in late June and early July by Zogby International for the Chronicle, showed that 54 percent of 800 Americans asked believed that "the shuttle program should not resume until the future of the space program had been re-defined." "

So there's at least a remote possibility that it finally gets truely re-defined, maybe even as much as they stop calling it a "program" ...

Posted by at July 21, 2003 10:50 AM

For some reason I haven't been able to comment here for months (occasionally part seems to get posted), but I'll make another attempt now.

The thing that hit me when reading the P.Rex column is that the shuttle design sounds like the 'of course' solution to a riddle that precludes any other design. Which is totally false.

Until we go nuclear, nothing is going to be more cost effective or have faster launch rates than a simple capsule on a staged vehicle. (Although that Israeli concept of launching from a balloon is some pretty cool outside the box thinking.)

The idea that wings provide reentry stability is just plain stupid... the stable shape is the tear, just put the heat shield on the bottom! It's idiot proof.

If you really, really need cross range capability (which you really, really don't) deploying a parafoil would do the job without all the parasitic weight (although the old fashioned round chutes probably make more sense.)

It's not going backwards to choose the best engineering choices. Any choices should be objectively examined against a base line. Only when performance exceeds the base line should they be considered. Every other argument is just pure bull.

Posted by ken anthony at July 21, 2003 01:02 PM

"Publius Rex" makes some good points, he's basically taking the shuttle-c idea out again if my memory is correct. Still there are a few questions I'd like to hear answers for:

The external fuel tank is not currently recovered after take off. If you mount the main engines beneath the external fuel tank you lose them as well. What does this do to the cost?

Is there anyway to make the external fuel tank/main engine combination recoverable?

Would replacing heat tiles with carbon-carbon do anything to help protect vunerable areas from falling insolation. If so what would be the cost/weight of such a plan?

Would a NASA plan to do such a thing kill the growing private space industry?

Posted by ruprecht at July 21, 2003 01:05 PM

If you really, really need cross range capability (which you really, really don't) deploying a parafoil would do the job without all the parasitic weight...

Because of the low airspeed and L/D of the parafoil (the maximum L/D of a reliably-deployable parafoil isn't much greater than 3:1), it isn't a very good way to provide cross-range capability: to get significant cross-range offsets, you'd need to deploy it at huge altitudes, leaving it at the mercy of the upper winds. Aside from that, deployment forces increase enormously at low air densities, driving the system to ever-larger drogues, more deployment stages/parachutes, and more failure modes. It's quite a tail-chasing exercise.

The effective cross-range of a lifting capsule (like Apollo, a bit under 20 miles), used from high-gate altitudes on down, would be as large as that attainable by a parafoil deployed at reasonable altitudes (i.e., ~20Kft). Basically, you're at best doubling your cross-range at the cost of much greater complexity...

If you mount the main engines beneath the external fuel tank you lose them as well... Is there anyway to make the external fuel tank/main engine combination recoverable?

There have been several proposals to package the engines as a recoverable subsystem; in fact, the large parafoils used on the X-38 were originally proposed to recover such an engine pod -- maybe even for a Shuttle-C variant, I don't recall all the details.

Posted by Troy at July 21, 2003 02:59 PM

You're probably right, not much benefit to a parafoil; but I had a wild thought...

Could a balloon be used? Deployed at the right point of reentry (if it were not too small a window) it could even heat itself?

Jules Verne would be proud!

Posted by Ken Anthony at July 21, 2003 03:29 PM

Would a NASA plan to do such a thing kill the growing private space industry?

Aside from diverting NASA resources for another decade or two, it probably wouldn't effect private industry. The vehicle has to be competively priced with private launch capability or highly subsidized to steal business from private launch business. IMHO NASA isn't big enough any more to eliminate private space industry.

Posted by at July 22, 2003 06:34 AM

Slightly off topic. In the book 2010 Arthur C. Clarke proposed using inflatable disposable heat shields. Is there any validity to this idea?

Posted by ruprecht at July 22, 2003 07:31 AM

Assuming they reconfigured the shuttle to be a Buran style vehicle with the engines beneath the external fuel tank.

How much of a glide improvement would you get by redesigning the rear of the shuttle to make it a bit more aerodynamic now that the main engines are no longer in the way? The old Enterprise had a different rear during the initial tests.

How much rebuilding is required to create the F-111 escape cockpit mentioned. That sounds like a significant redesign with lots of failure points. Seems a bit wishful thinking to me.

Would the solid rocket boosters be built into the external fuel tank/engine as they did on the Buran or would they be kept seperate for flexibility.

How long would it take to get the redesigned external fuel tank/engine combination (with a cargo pod attached instead of a shuttle) into service? How long to redesign the shuttle to remove the main engines?

Posted by ruprecht at July 22, 2003 07:40 AM

[I]If you really, really need cross range capability (which you really, really don't) ...[/I]

Actually, you [B]do[/B] need crossrange if you are an escape vehicle. The reason is this: for most of your time in orbit, you are over areas that are impossible to ditch into, since there are no search and rescue capabilities. The only places you can count on such capabilities are off the coasts of major industrial countries. Most of the ocean (mid-Pacific, mid-Atlantic, African coast, Asian coast, South American coast) have no SAR capability and no ship traffic. So either you have to loiter in orbit for a while until you can ditch off of the US, Europe, parts of Australia, Japan or the like or you have to be able to keep the crew safe in the ocean for quite a while. Either one requires more mass, and is a problem if the crew includes injured. X-38 had wings for a reason - lower g-loads and crossrange to get back to the first world.

Posted by Edmund Hack at July 22, 2003 12:25 PM

Re: Balloons and inflatable disposable heatshields.

There have been plenty of such proposals; search this page for MOOSE, Paracone, FIRST, Re-Entry Glider and SAVER. The Russians have also been playing with inflatable reentry/landing systems like this one, and within the last few years actually flew (and lost) an experimental stage-recovery testbed.

The late John Nicolaides (self-proclaimed inventor of the parafoil, although this is definitely open to argument) had proposed doing a direct reentry under an open parafoil, arguing that deceleration and heating would be mild in the extremely low-density upper atmosphere; however, he typically classified his results, so I doubt any of those proposals were properly peer-reviewed...

Posted by Troy at July 22, 2003 06:28 PM

And getting closer to the topic with escape systems: it has been often argued here and other places that a true routine orbital system would not have an escape system, any more than an airliner does (despite people like this. With enough redundnacy built into the system and enough testing, adding an escape system for routine flight can easily introduce more failure modes than it solves, driving reliability down instead of up...

Posted by Troy at July 22, 2003 06:38 PM


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