April 2, 2008 notes:
Our top priority remains getting an extremely reliable
engine that we can use for all of our projects.
We have been tuning startup / shutdown procedures and trying different
injector patterns to avoid heating zones on the stainless steel chamber and
face, and we think we are pretty close now.
We did a better rocket crane truck run with an improved
startup sequence and a longer burn time:
Normally during a test, either of a tethered vehicle or on
the test stand, I manually shut it down as soon as I see the engine chug when
the fuel line gulps its first helium. We
had always been worried about the effect on our graphite engines, and there
were similar worries about red hot stainless steel engines, but we hadnt seen
any real problems so far. We decided to
do a test to see what would happen if we just let the engine continue firing as
it ran completely out of fuel. We warned
everyone that this test would almost certainly wreck something, and might very
well result in a significant explosion if the engine completely flamed out,
then dumped a pint of mixed propellants into a red-hot chamber. The results were destructive, but not
For vehicle flights, we want the engine to keep firing, even
if it is eating itself alive. An extra
couple seconds with stainless steel hybrid assist might get the vehicle back on
the ground. The manual shutoff has
seemed to work out ok for us on the test stand, but an automated shutoff would
be safer and more consistent. We
investigated several different options, and wound up testing an optical liquid
sensor from McMaster-Carr, part number 5094K31. This worked like a charm. We did see some bubbles in the line on an
initial start once, so I now require a ten millisecond no-liquid signal for
shutdown. We dont have high hopes for
it working in cryo fluids, but we will probably give
it a try.
We wound up with two rings of F-O-O-F split triplets on the
injector to reduce the recirculation zones heating the injector face. This engine worked well for both many
And for sustained long burns:
The injector face is still clearly getting hot, and shows a
little pitting, but it hadnt changed any after the long full throttle run,
which is a harsher test than any of our normal hovering flights. This engine works well, but the mixture ratio
is quite a bit rich, giving unequal propellant depletion and lower Isp. Our next engine test will be with modified
orifice sizes to get higher Isp
and an equal depletion. If that doesnt
melt anything, we should be basically done.
We have started our cooperative work with NASA involving methane
propulsion. Getting some LNG to work
with turned out to be a much bigger hassle than expected. In the short term, we are getting the LNG
brought up from Houston
by the dewar, which is
certainly non-optimal. We are getting a
decent sized ISO tank installed soon, which will allow us to top off our own dewars.
The day after the dewar
showed up, we tested an igniter with it.
We decided to use a thermal vaporizer for the methane, just like we do
for the lox, to give us gas-gas combustion in the igniter. Our vaporizers are old peroxide catalyst pack
chambers with all stainless screens in them (no silver), which take a cryo liquid up to room temperature gas for ten or fifteen
seconds of flow. We painted the methane
one red all over so we would never mistakenly use it for lox again. We normally use a 0.088 diameter gas orifice
for gox to go with a 0.032 liquid alcohol orifice
and out a ¼ or 5/16 diameter nozzle exit.
We used the same 0.088 sized orifice for the gaseous methane, which gives
a mixture ratio well rich of stoichemetric, but we
probably cant run it for tens of seconds in a row without burning it out.
The one surprise we had was that with the gox inlet closer to the igniter nozzle than the methane and
the spark plug opposite the methane, it wouldnt light. Swapping the lox and methane inlets made it
work fine. We made a series of tests
over a range of feed pressures:
We did this set of tests by loading the methane with the low
tech two vented ball valves with an AN fitting in between arrangement that is common for a lot
of small cryo operations, and we hated it. As soon as we got the parts, we converted
over to the Parker micro-bulk cryo quick connects
that Tex Air Cryo has always used for our lox
equipment. They are pretty damn
expensive, but it is so much nicer. They
dont have a specific keying for LNG, so we used the nitrogen keying, because
it is farther away from the lox bayonet keys than the argon keys.
We dont have a second valve set up for cryo
conditioning the methane line for engine testing, so we tried to elevate the
lines as much as possible to let the warmer cryo
fluids rise, but we still had a noticeable gas bubble in the first couple
seconds of firing.
We have had a number of inquiries from government agencies
and Google Lunar X-Prize teams about possibly buying or commissioning one of
our vehicles for research or prototyping purposes. The way to look at it is as a rocket trainer,
rather than a vehicle that can perform any kind of real lunar or suborbital
mission. We dont pretend that the
vehicles could actually land on the moon, but if you want to hack on a real,
flying system, there is a lot of value to be had.
The price is $500k. The
experience of the Lunar Lander Challenge shows quite clearly that you arent likely
to do it yourself for less, even if you spend a couple years at it. Several intelligent and competent people
thought otherwise, and have been proven incorrect.
You can have either a module or a quad, at your choice. The quad has more hover duration, but it is
more of a hassle to operate. A module
could be fulfilled right now, a quad would take about
three months to build, since we are still planning on using Pixel for LLC this
year and other tasks. The engine will be
one of our new film cooled stainless chambers, and we will warrant it for ten
flights. If it blows up or burns through
in that time frame, we will replace it.
We will not replace the vehicle if it crashes, but historically our
engine problems have been visible at startup, and you should have an
opportunity to abort the flight. Ground
support equipment is included, except for the lox dewar(s),
which would be specific to your local lox vendor. We will test the vehicle ourselves, then train your crew to operate it. You get copies of our experimental permit
applications and information about the insurance policies we use for permitted
flights. Details on modifications to the
flight control software are negotiable.
Going to different tanks, engines, or propellant are
possible, but the cost will go up.
There was a lot of talk recently on the web and at Space
Access 08 about XCORs Lynx announcement. I am an investor in XCOR, but Armadillo and
XCOR are also now pretty much direct competitors, so read whatever combination
of bias you want into the following statements.
XCOR and AA firmly agree on several points build the
smallest possible vehicle that can serve a market, use only inexpensive liquid
propellants, and design the vehicle to cycle several times in a day instead of
using a big vehicle that flies more people less often. We split on the classic HTHL / VTVL argument,
but the marginal operating costs of our vehicles will likely be quite similar.
I might as well run through and give the John Carmack opinion on all the usual suspects in suborbital
Scaled / Virgin is the safest bet for success. Outside of the X-15, Space Ship One is the
only example of a reusable, 100km class manned vehicle. Everyone else, us included, requires a lot
more extrapolation for an investor to believe in, and the problem isnt nearly
as trivial as some people like to make it out to be with the There are no
technical challenges, just give us the money! lines. It is not true that any old team could have
won the X-Prize if Paul Allen had given them $20 million.
Air launch and feathered reentry do have some real safety
advantages. However, they are spending a
frightful amount of money, their schedule has slipped a lot, and the configuration
is inherently much lower in operability than the others. The fatal explosion at Scaled has also
forever ended the nitrous hybrids are inherently safe argument. I am confident that they will fly customers,
and if they dont have any competitors, they may eventually turn a profit. If a more highly operable vehicle is
competing, SS2 probably wont earn out.
Virgin has no exclusive ties to Scaled, and they will be happy to fly
their customer backlog on any vehicle that they can.
Blue Origin is still shrouded in secrecy, which lets a lot
of people project their fondest hopes onto them with little evidence to the
contrary, but the federal experimental permits give us some insight into what
they are doing. Last year, they
conducted one short experimental-permitted launch that they showed online, and
one other one for which we have no public data.
One could speculate that they might have done a spectacular 100km flight
on their second shot, but that would be, well, silly. They have the funding to go head to head with
SS2 if they choose, but they have not stated that as their plan and there is
evidence that they dont intend to. It
looks like they want to play in the orbital space, and perhaps dont want to
get bogged down competing in suborbital space.
I think that is a mistake. If
Jeff Bezos is reading this, drop me a line sometime
Rocketplane was kicking around,
raising money long before we showed up on the scene. They have burned through tens of millions of
dollars of funding, and nothing has ever left the ground. Would another ten or twenty million dollars
do it? I doubt it very much.
SpaceDev is a real company with
real revenue, they have hardware in space, and they did significant work on the
propulsion system for Space Ship One, but their only in-house vehicle work was
a hybrid lunar lander that flew up a set of guide
wires last year, and didnt look all that good in the process. I also think the hybrid powered VTHL DreamChaser is about the worst design for commercial suborbital
flights. They arent going to build it
on their own dime, and it looks like it would be a very expensive development
project that would end up with quite high operating costs if it was ever
EADS Astrium. Oh, please.
XCOR has flown two rocket powered airplanes and gone through
many engine development cycles. The Lynx
is designed around engines that are essentially in-hand right now. XCOR has stated that they need to raise nine
million dollars to build the mark 1 version, and an additional twelve million
for the mark 2 that can actually reach 100km.
I think they can probably do it.
Armadillo Aerospace. Anyone can go back through this website and
watch us crash vehicles and blow up engines over and over, while never getting
more than a few hundred feet off the ground (and that one was, uh, unintentional). It isnt hard to discount what we do and gaze
admiringly at a slick press release speaking to the dreams of the future. Some people doubt the value of experience, or
think that the experience will just materialize when the investment lands, but lets go over a few things:
We have built and flown so many different vehicles now that
I dont even count, but lessons are learned from each one. We have experienced and solved issues eerily
similar to the things that downed the first two Space-X Falcon launches, among
many others. We have more reusable rocket
powered vehicle flights than everyone else here put together, although XCOR is
gaining ground with rocketplane flights. Scaled made the X-Prize flights under a
launch license, and Blue Origin has made two flights under experimental permit,
but we have made many more free flights under AST experimental permit than both
of them combined. As far as a rocket
engine is concerned, a three minute hover is as hard as a 100km suborbital
flight, and we have had weekends where we did more vehicle burn time than all
the flights of Space Ship One combined.
Total cost to date, about $3.5 million. I think it takes two million more of
dedicated funding to put a man to 100km on our Six-Pack, and another million
dollars for a flight test program of a hundred launches before entering
commercial service. There are lots of
challenges, and we will probably crash a few more vehicles before we get there,
but I continue to think we are a good bet, and the virtues of modular rocket
systems will probably turn out larger than most people expect.
Some people will never be comfortable in a VTVL, but the
fishbowl cabin will be an experience like no other. I think the market would be quite happy if
Scaled, XCOR, and Armadillo all delivered vehicles. I still think there is a chance we might be
first, depending on how Scaled chooses to play things.