Space Access Update #131 3/24/13
Copyright 2013 by Space Access Society
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In this Issue:
- NASA
Tech Data Drought
- The
Race Is Far From Over
- Free
Advice
- "Warning
Shots" Correction
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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.
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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.
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Free Advice
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.
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"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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