Space Access Update #131 3/24/13
Copyright 2013 by Space Access Society
In this Issue:
- NASA Tech Data Drought
- The Race Is Far From Over
- Free Advice
- "Warning Shots" Correction
NASA Tech Data Drought
Word started bouncing around the community earlier this week that NASA's National Technical Reports Server (NTRS), home to huge amounts of non-classified aerospace technical information, had gone dark. Speculation quickly started that this was a NASA reaction to growing Congressional pressure over foreign access to sensitive NASA data.
The speculation was quickly confirmed. NASA has shut down NTRS access pending a review of all papers on the site for any that should be export-restricted. This could take a while, as NTRS hosts many thousands of reports covering a period from the early days of aviation forward.
We do not wish to get into a discussion of precisely what level of export control of aerospace technical data is appropriate. The answer is clearly not zero; there are in fact parties out there working on the capability to fast-deliver lethal packages to addresses including ours. US taxpayers shouldn't pay to help them to get better at it.
The answer is clearly not 100% restriction either. ITAR tech-export rules that fall well short of that level have already done considerable harm to the US space industry, hurting US exports and hampering international cooperation.
On the whole, we support sensible relaxations of the current tech-export rules.
One of the reasons why is clearly illustrated by the current situation. Shutting down NTRS immediately on a guilty-till-proven-innocent basis hurts US aerospace students and researchers, aerospace historians, amateur rocketry enthusiasts, and small-to-medium aeronautical, rocketry, and space companies - a wide range of groups and individuals unable to afford their own comprehensive technical research libraries.
Meanwhile, the foreign entities Congressional ire is aimed at very likely downloaded and stored locally the complete NTRS contents ages ago.
Once again, our government has tried to defend us from hostile foreigners, but ended up shooting us in the foot. We urge that Congress work with NASA for a quick resolution of this mess and the return to online availability of the nation's unclassified aerospace archives.
If we must have stronger restrictions, apply them only to new publications in future. Even if some of the papers on NTRS do turn out to be ITAR-marginal, that horse left the barn a long time ago. If there's one thing we all should have learned by now, it's that once something is on the internet, there's no practical way to lock it back up again.
The Race Is Far From Over
"It ain't over till it's over" said the immortal Yogi Berra. We're reminded of this because a colleague recently complained to us that this new affordable-space race is all over, SpaceX and Blue Origin have won, everyone else might as well pack up and go home.
All due respect to SpaceX and Blue Origin (and a great deal of respect is due; they're accomplishing remarkable things) we're with Yogi. This race is just getting seriously started. Here's a somewhat rambling stroll through the reasons why we think this is so.
Putting on our dispassionate industry-analyst's hat...
SpaceX demonstrably does a number of things very well. They've developed and flown the Falcon 9 expendable booster for a tenth of what NASA estimated it would have cost NASA to do (and a fifteenth of what recent history indicates it'd actually cost NASA.) (See Space Access Update #128; the "recent commercial booster development" referred to in the first section was F9.) They've also developed and successfully flown an initial version of the Dragon capsule. Both booster and capsule have entered revenue service, and SpaceX's combination of pricing and early F9 flight success has now sold several dozen F9 launches over the next few years, the majority of these to non-NASA customers. Meanwhile, Falcon Heavy is due to make its first flight in the next year, delivering double the payload of any other currently operational booster.
But SpaceX has a lot on their plate. The biggest immediate hurdle we see is transitioning F9 from development to factory production, while both maintaining the high degree of process control needed for reliability, and also keeping production costs low enough to make money at their highly competitive prices. We wouldn't bet they can't do it, mind. But they'll have their hands full with it. And with bringing Falcon Heavy online, and with continuing Dragon development for crewed operations.
We consider it possible that their efforts to also develop a reusable booster may end up taking quite a while. The first rule of all projects is, it'll take longer and cost more than you first planned. (Our industry as a whole has been illustrating this in recent years, as many have noticed. Unlike many, we don't view this with any particular alarm - as we said, it's the first rule of ALL projects.)
And from a cold-eyed business analysis viewpoint, SpaceX may be just fine with this, if in the meantime the publicity they give to pursuing reusability happens to cause fear, uncertainty, and doubt in the minds of rivals in the expendable launch industry. The expendable launch industry where they happen to be currently carving out large chunks of market share and (we see some signs of) beginning to increase the overall market size.
We don't assert that SpaceX is not serious about reusability, mind. Just that between everything else they have on their plate, and another factor we'll get to in a bit, it may take them longer to get reusable boosters into revenue service than you might expect.
Blue Origin, meanwhile, is also doing remarkable things, to the extent we can tell what they're doing. They seem to have a practical plan for a reusable crew vehicle and a reusable VTVL first stage that could fly suborbital missions on its own and orbital missions with an expendable second stage. They seem to have built a highly skilled and adequately financed development organization that is proceeding with this plan at a measured pace. They do a limited amount of specific highly focused flight test. And they don't talk a whole lot about any of it, which seems a legitimate business decision given the assumptions that they expect competition and they don't yet need to raise significant outside funding.
This brings us to the core of why we think the race is far from over: The vast majority of current commercial flight experience with launch and recovery of reusable rockets lies not with either SpaceX or Blue Origin, but with Armadillo, Masten, Virgin, and XCOR.
None of these companies (with the possible exception of Virgin) is funded in the same class, none of these companies is yet going for orbital markets, all are currently aiming for the smaller (but growing) suborbital markets. But among them they already have hundreds of flights of reusable vehicle experience (versus perhaps a dozen between SpaceX and Blue Origin) and if things go even partially as planned, over the next few years they will increase their flight experience totals many times over. And we're pretty sure they all intend to go for the orbital market once they have suborbital mastered.
Flight experience matters, a lot, in developing reusable aerospace vehicles. Going from ground level through subsonic, transonic, and supersonic flight to free-fall/vacuum flight, then back down again, involves much vehicle stress through multiple tricky aerodynamic and flight-mode transitions. The suborbital reusable companies already have a significant lead in this department, a lead that is likely to multiply over the next few years. We can't help thinking that this could be a major equalizer in the orbital reusable competition to come.
A quick side note about an obscure point of aerodynamics, while we're at it.
Blue Origin a couple years back was flight testing a reusable first stage demonstrator that crashed, after "a flight instability drove an angle of attack that triggered our range safety system to terminate thrust on the vehicle" at mach 1.2 and 45,000 feet. If you look at the pictures the nose of the cylindrical vehicle was covered with a plain hemispherical endcap, with not much visible concession to aerodynamics.
SpaceX's Grasshopper reusable rocket testbed, meanwhile, is also a simple cylindrical stage with a relatively blunt nose with not much visible concession to aerodynamics, also with supersonic flight tests planned.
The following observation comes from a senior DC-X project veteran - any garbling is probably our fault. DC-X flew with a series of narrow strakes (long skinny fins) on its nose, to avoid problems with something called asymmetric vortex shedding.
Briefly, a rocket nosecone at transonic speeds (IE in the neighborhood of mach 1) at small angles of attack (IE rocket maneuvering causes the nose to not be pointed precisely in the direction of travel, so air comes at it slightly off-axis) can be prone to trailing a large vortex, a rapid swirl of air, on its downwind side. The vortex can then cause a region of significantly reduced pressure on that side, producing surprisingly large side forces on the vehicle nose that can exceed available control authority and send it out of control.
DC-X's nose strakes, as we understand it, were designed to prevent one large vortex forming at significant angles of attack by breaking it up into several smaller, more manageable vortices.
Based on the limited information available, it is plausible that Blue Origin's 2011 problem was caused by transonic asymmetric vortex shedding causing a loss of control. Based on the limited information available, SpaceX Grasshopper could be vulnerable to similar problems when it reaches transonic speeds.
Then again, Blue Origin's problem could have been something else entirely, and SpaceX may already have it covered. But, we figure it can't hurt to pass the tip on.
"Warning Shots" Correction
In our recent piece "Warning Shots", we ran ballpark numbers on whether, if tomorrow we sighted a comet inbound toward Earth (similar to the one recently spotted heading toward a very close pass of Mars), current world space capabilities would give us any chance of deflecting it enough to make it miss us. The answer was a qualified "maybe".
Since then we've looked into the matter a little more, and the "maybe" has gotten a lot more qualified.
(Short version, for those of you whose eyes would glaze over on the tech details, any attempt to steer an inbound comet away from us using what we currently have would be a long shot, with major unknowns and far too much chance of failing. Better than having no shot at all - but there are a lot of highly affordable, even profitable, things we could do to quickly improve our chances. We need to get started doing them. You may now skip the rest of this piece...)
To briefly recap: We estimated the energy needed to shift the comet's course by 5 meters a second (enough to make it miss us if we can do it while the comet is still a month away) at about 25 megatons (measuring the energy in terms of the most compact energy-delivery devices we have, hydrogen bombs.) We estimated that current world launch capacity, given two years notice, could put perhaps 250 megatons worth of hydrogen bombs on course to intercept such a comet roughly a month before it got here - ten times more energy than the minimum needed to accelerate the comet out of our way.
Our next paragraph illustrated two of the hazards of publishing an initial ballpark estimate:
"Alas, it's not that easy. Bomb energy needs to be transformed to comet motion, and there will be losses. We can't afford to shatter the comet; our best hope is to set the bomb(s) off nearby, so they heat one side of the comet just enough to boil off volatiles and gently propel it sideways. At minimum we lose half of each bomb's energy to open space, and the other half is unlikely to be converted to comet motion with anything like 100% efficiency. Absent better data, we'll assume 20% of that 50% gets converted to comet motion, for an overall efficiency of 10%. (Even that may not be trivial to achieve.)"
We were cautious, yes - but not cautious enough. "Not trivial to achieve" turns out to be a bigger understatement than we thought.
We may have allowed some wishful thinking to creep into our assumption of 10% efficiency - it's not like it wasn't obvious that's about what's needed. This sort of thing is always a hazard in doing estimates; your goals can bias your assumptions.
But the real error we made was in not pursuing a bit further just what efficient energy use implies in terms of the mechanics of moving large space objects.
There is no such thing as a reactionless drive, where you pump in energy and cause just one object to move. It'd be nice; we'd be typing this from our vacation condo with the view of Olympus Mons were it possible, but alas Newton's Third Law ("for each action there is an equal and opposite reaction") remains in force. If you want to move A, you need to push B in the opposite direction, and A's mass times its velocity change will equal B's mass times its velocity change. MV = MV, no known exceptions.
Short version, if we must have 10% energy efficiency, boiling off comet surface material with nearby bomb-detonation energy is right out. The energy required for velocity is one-half of the mass to be moved, times the square of the desired velocity. X times faster motion requires X-squared times more energy. The vast majority of our energy would end up in the (high-velocity) boiled-off vapor; only a tiny fraction would end up in the (low-velocity) main comet body. Chase the numbers a bit and you end up needing many thousands of megatons to move our comet that way.
We've already built many thousands of megatons of bombs, mind. What we can't currently do is get the few thousand tons of bomb mass involved out there in time. Oops.
Getting back to what we currently could do, 10% energy efficiency in moving the main comet body comet turns out to imply using our total available energy to pry loose and propel away roughly one-tenth of the comet's mass in the opposite direction, at around ten times the velocity we want for the main comet body.
So, if we have a 30 kilometer comet to move at 5 meters a second, and only 250 megatons of devices to do the moving with, we need to use them to blast away about a tenth of the comet's mass at an average of about 50 meters a second.
In other words, we would need to somehow set off our devices deep under the comet's surface and blow off very large chunks of it at relatively low velocity. And no, we don't get to do this Bruce-Willis-in-Armageddon-style by drilling holes then sliding bombs down them - the comet is inbound at near 30 kilometers a second, while our interceptors are outbound at perhaps a tenth of that. Rendezvous and landing isn't even close to an option with current technology.
Useful calculations of hypervelocity deep penetration of a rocky snowball by nuclear warheads probably would take much classified data and supercomputer time. But our suspicion is getting that to work reliably the very first time at more than thirty kilometers a second might be too much to hope for.
Some scheme that'd use smaller devices to excavate deep pits followed closely by larger devices that'd go off at the bottom and blow loose large chunks of comet strikes us as slightly less implausible. One obvious unknown is the general internal composition of comets, never mind the specific internal composition of our target. One obvious risk would be devices colliding with debris thrown up by previous devices. And then you get into all the interesting details of device physics.
It's entirely possible that the people who have a detailed handle on such things would look at the problem and tell you, "forget it, we'd be hosed." Or perhaps they'd say "it might just barely work - let's give it a try."
Our take on all this remains that "it might just barely work" isn't good enough. We should accelerate development of the range of capabilities that'd give us better odds that are also relatively cheap, pay for themselves in other ways, or both. These mostly boil down to, better knowledge of what's out there, and better transportation to let us get more mass farther out there faster.
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