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Official Armadillo Q&A thread

Posted by: John Carmack - Tue Jun 15, 2004 8:01 am
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Official Armadillo Q&A thread 
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Rocket Constructor
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Post Re: Altimeter & safety   Posted on: Sun Jun 20, 2004 5:30 am
Alex A wrote:
In manned vehicles, how do you intend ensure crew safety if the engine fails (seems a critical single-point failure). The crew could bail-out & use personal parachutes, but that wont work at low altitudes (not enough time).
Fitting parachutes to vehicle is probably out as you'd be back against range safety contraints due to wind drift. Maybe crush-zones and/or air-bags on the tail?


This was similiar to my question; do you think it would be feasible to integrate the old parachute-recovery design into the new rocket as a failsafe mechanism? Like Tony said, no one should be worried about drift when you're in a life-or-death situation.

Also, in reference to Bulldog's "MDAIC WCFM MEF" scenario: Are you ever worried that demons will, say, come through a gate on Phobos and you, John Carmack, armed only with a pistol, will have to save the day?

(I'm sorry man. I just had to.)

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Post    Posted on: Sun Jun 20, 2004 6:28 am
<< This was similiar to my question; do you think it would be feasible to integrate the old parachute-recovery design into the new rocket as a failsafe mechanism? Like Tony said, no one should be worried about drift when you're in a life-or-death situation. >>

The problem is not one of feasibility. Integration of a chute style recovery system would be a trivial affair. However, life-or-death does not enter into the equation.

The stumbling block is the AST mandate (not of their making) that we consider an RLV to be 100% guaranteed to fail, at the worst possible time, and in the worst possible way - MDAIC WCFM - and then look at the MEF. For a parachute, the worst case is a premature deployment (don't you just hate it when that happens :-) at an altitude that just guarantees its survival in the 3-sigma wind conditions. For our X-Prize vehicle that calculated to be a 70-mile drift potential from the range lift-off point! This causes two problems;
(i) The Ec calculation for third party fatality becomes much messier and insurance more costly because of the greatly expanded MEF.
(ii) White Sands Missile Range frowns on hardware leaving the range and wants some degree of autonomous control at great cost and delay. Their real preference is a flight termination system that involves explosives and small pieces fluttering gently to the ground. Pilot Russ Blink was not enamored of this option - wuss!

After we got over the annoyance factor at the futility of it all, it actually worked out for the best. It got us back on the powered landing mode and RLV's that set down on the same pad they lift off from, Buck Rogers style, are really cool!

The more we learn at Armadillo the truer the old Von Braun adage appears;
"We can overcome gravity, but the paperwork is overwhelming."

I may be rambling! It's 1:30 a.m. and we just finished our Staurday session at the shop. John's report should be imminent. More lesson's learned.

Neil M


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Post Jet vanes   Posted on: Sun Jun 20, 2004 9:09 am
It would seem that 3 jet vanes have enough degrees of freedom for full control of the vehicle.

Why are you using four? Is it the simple orthogonality and not messing around with 120 degrees and coupled response? Can they provide redundancy against actuator failure?

(joining everyone's admiration and thanks for doing this and reporting it all so openly in your updates)


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Post    Posted on: Sun Jun 20, 2004 2:32 pm
quick one here, do you plan on going public on the stock market ever?

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Post    Posted on: Mon Jun 21, 2004 9:50 am
John, following your hot-engine run I was wondering what your longest engine run to date has been, on an engine close to your current design?

Also I was interested in my previous question to know whether or not you did decouple the position-holding from roll; since I think I could easily make a case that drifting around to 90 degrees is not spin stabilised!


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Post Replies #3   Posted on: Mon Jun 21, 2004 8:39 pm
multiple throttle valves:
I'm confident we can solve the low flow oscillations in software, without needing any additional hardware.

vehicle CG:
The small vehicle balances about a foot above the lower skirt mating point. The shocks are actually as far out as they can go, given the square mounting flanges and square support tubes. The vehicle has a foam bumper strip around the base of the nose cone, so there is a pretty good chance we wouldn't hurt anything on a tip-over. Future vehicles are going to have the electronics at the base, so even if they tip over, there is nothing much to hurt. up top.

ullage gasses:
We only load propellant immediately before launch, and once it is pressurized you really can't evaporate any gasses. In any case, we have some old reports about storing a slightly different mixed monoprop in drums for six months in the 50's without any problems.

slosh:
The big vehicle has some slosh baffles on the manway, but there is nothing in the small one. We aren't planning on doing anything significant until it proves to be a problem.

propellant name:
We just call it mixed monoprop.

engine theory:
As far as I know, we are the only people to ever do a solid catalyst mixed monoprop engine, so our work updates are the only reference available. It is a lot of reading, but all the technical improvements we had to do to make it work are in the notes.

radar altimeter:
We used a laser altimeter on the old seated lander, and I have considered a radar altimeter as a way of avoiding problems with any kicked up ground dust (Rocke has a decent unit for around $10k), but the GPS seems to be working well, and it avoids having to expose a sensor on the hot side of the vehicle. We have been planning on using differential GPS, but regular GPS with an altitude uncertainty and some restrictions on launch windows for consistent satellite views may be just as good.

abort systems:
We have redundant cutoffs, so we are very sure that we can make the vehicle stop thrusting, but there are no functional abort modes. We would like to carry a parachute as a backup, but it doesn't look like we will be able to have that automated without running into licensing problems due to misdeployment issues, but we may still be able to have it as a manual pilot option. If we can't use a full parachute, we would probably just add a stabilization drogue to allow a pilot bailout.

commercial use:
Once it is developed, we certainly hope to be able to recoup the development cost with commercial use... Non-human payloads are a given, and we definitely want to carry people, but insurance may still be an issue there.

post X-Prize plans:
Now that it looks like Scaled has a lock on it, we are definitely scaling down the vehicle. We aren't even going to look at 100km flights until a commercial spaceport that we can use is licensed (we can't use Mojave, because they are only for HTHL vehicles). I'm not going to give White Sands over a million dollars to allow us to test our vehicles just for grins. We will concentrate on getting rock solid reliability within the limits of waivered flights instead of licensed flights.

orbital:
My pet plan for orbital has been "boosted SSTO" for quite some time. This is basically the plan described in "The Rocket Company" serial on Hobby Space -- a straight up / straight down booster, and a very high performance upper stage. I think there are strong engineering and operational reasons for this, even though it looks like an inefficient staging point at first glance.

growing the team:
No, not at all. It is a challenge to keep the current team size operating at high efficiency, adding more people would only get in the way. If a local certified aviation tech wanted to join the team I would probably take them, but that is about it. I do often get good suggestions and ideas from people online, but ideas and analysis are really a fairly small part of the effort.

patents:
I have no plans to patent anything. If I have publicly disclosed something, no one else can patent it either. I have been actively encouraging some other teams to follow in our footsteps with mixed monoprop engines and jet vanes, but it seems like everyone wants to differentiate themselves by doing something different.

three jet vanes:
I have been considering it for future vehicles, but the current control system thinks about independent axis, and I didn't want to try changing both the actuation method and the control system at the same time. Now that we know that jet vanes work for us, writing an experimental control system for three vanes may be a good test.

stock market:
I have no intention of ever taking a company public. The last thing I want is a board of directors telling me that my development methods and tactics are not optimal for company returns.


John Carmack


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Post    Posted on: Mon Jun 21, 2004 9:23 pm
I'm interested to know how you met/came in contact with your current team.


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Post    Posted on: Tue Jun 22, 2004 1:41 am
<< I'm interested to know how you met/came in contact with your current team. >>

I can answer that one, at least for the original team members. After consuming every book on rocketry in sight John had asked the local rocket club DARS (Dallas Area Rocketry Society) if they knew of anyone in the area that might be interested in doing something a little out of the ordinary. Russ Blink, Phil Eaton and I were about as far out on the limb as you can get and we all attended that first meeting ... A long time ago in a galaxy far, far away! At that time I don't think any of us envisaged that we would be doing what we're doing today. Matthew Ross works with Anna, John's wife, and Joseph Lagrave is an independent contractor who did a lot of construction work for us in the early days.

More recently we added Tommy Bishop, who works with Russ and Phil, James Bauer who is a welding guru, and John Carr, a combustion chemist. It's a kind of unique mix of talents, abilities and personalities, but John is definitely the driver behind the program. It's tough sometimes to keep pace with number of new ideas he comes up with ... I'm glad to say :-) For someone like me who grew up the wrong side of the pond with October Sky syndrome, this was just about the best thing that ever happened for me (my beautiful bride and three sons excluded of course!) I know that the other team members are equally enthusiastic which is why we can acheive so much, in such a short time and at relatively little cost.

Neil Milburn


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Post    Posted on: Tue Jun 22, 2004 1:46 am
Mr Carmack, I voted for your team as "my favorite" on the poll, and you have done an admirable job getting publicity, but how is your team progressing in comparison with the DiVinci Project, Starchaser Industries, and Canadian Arrow? (Let alone Scaled Composites)

When will you have a manned vehicle?


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Post Well John, you're not out of the running!   Posted on: Tue Jun 22, 2004 5:05 am
:twisted:

Had my widget T-shirt on all day!

Looks like SS1 has some serious controll problems they need to address.

So...I have two questions

1. How does it feel to be a Space counter culture hero?

2. Ya gonna go for it?


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Post Re: Replies #3   Posted on: Tue Jun 22, 2004 11:31 am
John Carmack wrote:
abort systems:
We have redundant cutoffs, so we are very sure that we can make the vehicle stop thrusting, but there are no functional abort modes. We would like to carry a parachute as a backup, but it doesn't look like we will be able to have that automated without running into licensing problems due to misdeployment issues, but we may still be able to have it as a manual pilot option. If we can't use a full parachute, we would probably just add a stabilization drogue to allow a pilot bailout.


Would you consider a solid rocket 'launch escape system' for low-altidute aborts (when too low for parachute to work)?


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Post Re: Replies #3   Posted on: Tue Jun 22, 2004 11:43 am
John Carmack wrote:
post X-Prize plans:
Now that it looks like Scaled has a lock on it, we are definitely scaling down the vehicle. We aren't even going to look at 100km flights until a commercial spaceport that we can use is licensed (we can't use Mojave, because they are only for HTHL vehicles). I'm not going to give White Sands over a million dollars to allow us to test our vehicles just for grins. We will concentrate on getting rock solid reliability within the limits of waivered flights instead of licensed flights.

orbital:
My pet plan for orbital has been "boosted SSTO" for quite some time. This is basically the plan described in "The Rocket Company" serial on Hobby Space -- a straight up / straight down booster, and a very high performance upper stage. I think there are strong engineering and operational reasons for this, even though it looks like an inefficient staging point at first glance.


To avoid launch contraints/licensing, how about renting (buying?) a vessel with a helipad & launching from International waters?

What sort of performance would you get if you stuck the small (2ft) vehicle on top of the 'large' vehicle as a quick & dirty 2-stage system?

BTW you team's openess is refreshing & undoubtedly winning you many fans. However, I hope anwsering our questions is not to much of a distraction! Keep up the good work.


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Post    Posted on: Wed Jun 23, 2004 12:31 am
Any thoughts on developing an aerospike engine? That seems to be something that would go well with a high performance rocket system.

Thinking on what Alex said, is there any other possible alternatives for your test launches? I would think that carting everything over to Mexico is a remote technical possibility but would probably be an even greater legal headache.

Edit:
I just read in another thread that Scaled doesn't intend to make an X-Prize attempt until they figure out some of the anomilies and that SS1 is grounded until they figure out why the flight control system failed. If this is true would you still be scaling down the vehicle?


Last edited by TJ on Wed Jun 23, 2004 2:23 am, edited 1 time in total.



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Post    Posted on: Wed Jun 23, 2004 2:12 am
Great Murphy's Law update!

1. What are you using for inertial navigation/orientation other than GPS?

2. What sort of GPS antenna system are you using?


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Post Re: Replies #3   Posted on: Wed Jun 23, 2004 3:33 am
John Carmack wrote:
abort systems:
We have redundant cutoffs, so we are very sure that we can make the vehicle stop thrusting, but there are no functional abort modes. We would like to carry a parachute as a backup, but it doesn't look like we will be able to have that automated without running into licensing problems due to misdeployment issues, but we may still be able to have it as a manual pilot option. If we can't use a full parachute, we would probably just add a stabilization drogue to allow a pilot bailout.

post X-Prize plans:
Now that it looks like Scaled has a lock on it, we are definitely scaling down the vehicle. We aren't even going to look at 100km flights until a commercial spaceport that we can use is licensed (we can't use Mojave, because they are only for HTHL vehicles). I'm not going to give White Sands over a million dollars to allow us to test our vehicles just for grins. We will concentrate on getting rock solid reliability within the limits of waivered flights instead of licensed flights.

John Carmack


That comment about the abort system is interesting. I remember that the original Mercury Redstone flights had Shepherd and Grissom carry parachutes in case the main chute failed to deploy, but they probably wouldn't have done them much good. Grissom reportedly said "Well, at least putting it on will give me something to do untill I hit the water." It would have more utility in your design, I'd think, because you'd know very quickly that you had to use the parachute and get it on quick. If an engine failure occured at 90,000 feet the pilot could start putting on the chute immediately, as opposed to the Mercury system where you wouldn't put it on untill the main and backup chutes failed at about 9,000 feet. Still, lacking a full pilot or capsule eject system does make an engine explosion rather difficult to survive. I know that your engines are supposed to be very reliable, but one speck of the wrong kind of dust into hydrogen peroxide and BOOM! Nice fireworks, but bad for our brave little armadillo...

I'm a little dissapointed to hear that you'll scale back your vehicle size because of the SS1 flight, but as long as you guys keep working I'll be happy. Have you tried to fly anywhere else besides White Sands? It would be pretty far to lug all of your equipment, but Woomera, Astrauila is dying for any users it can find. They've practically been begging Kistler and Starchaser to fly there, and I'd bet they'd be much more welcoming than White Sands to some visionary astropeneurs. Come to think of it, is there any law that says you can't fly to space in your 100 acre test site? I mean, if you own the property, can the government stop you?

Just a few more questions:

I've been wondering for a while how you plan on dealing with the heat from reentry being focused directly on your engines when the rocket comes back from space. Will this be a problem? Will they need some heat protection?

If NASA were to say that in the first batch of Centennial Challenges they would offer $200,000 to whoever could demonstrate powered landing technology for a Moon lander the best, would you go for it? For that matter, if the offered X Prize-level money later on for a full-up lander would you take a stab at that? Both seem like they're right up your alley.

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