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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    Posted on: Wed Jun 23, 2004 11:30 am
Mr. Carmack,

are you going to stick with peroxide as fuel now that you are not aiming any more for the x-prize: isn't it so that peroxide can not give you enough efficiency for more ambitious flights. I'm also wondering if you're planning to stick with pressure fed engines (with a low efficiency) or intend to eventually go for pump fed engines (have you ever had a look at the pump-concept from flometrics??). Now that your team isn't going to persuid building a 'big rocket' any more do you think about testing 'more advanced' concepts on small rockets?

Thnx, Roel


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Post    Posted on: Wed Jun 23, 2004 2:16 pm
<< 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? >>

Ah grasshopper, let me enlighten you! As US citizens an Armadillo launch will fall under the auspices of FAA ASt regardless of whether we fly from Australia or Zambia. As such the license to launch will require both safety and environmental reviews. What Australia offers is wide open spaces and a willing spaceport operator (and good beer), but the same problems remain re licensing. Take a look at the AST pages on the www.faa.gov website for more info than you would ever want to know!

Another option would be a water based launch from a barge in the Gulf. Still a licensed launch but tough to find anyone to hit out there so the Ec calculations become a moot point. Question is, can Armadillo's swim?

Bottom line to your question is the 100-acres will forever be limited to about 3,500 ft AGL. Proximity of DFW glide paths, a target rich environment and environmetnal concerns would all make this a non-starter ... and reasonably so. A two-ton vehicle dropping in from altitude could really ruin your weekend.

Neil Milburn


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Rocket Constructor
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Post    Posted on: Wed Jun 23, 2004 3:52 pm
I find the idea that the US government can stop you from launching in other countries to be absolutely sad.

Maybe you should find some one in Australia who can be your "friend" and he or she can launch your rocket for you. Oh, and you might coincidentally be there to watch. It would be an amazing coincidence if you were there to watch your australian "friend" launch a rocket that you designed.


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Post    Posted on: Wed Jun 23, 2004 4:16 pm
Hi, John!

My question is: Why did you choose to go with H202 as monopropellant
when its sealevel Specific Impulse is only slightly greater than 160 seconds,
whereas H202 as both oxidizer and part-propellant with either UDMH or kerosene have much higher Specific Impulses?

i.e., Sealevel Specific Impulse of H202/Kerosene = 273 seconds;
[320 seconds (vacuum)].

Sealevel Specific Impulse of H202/UDMH = 278 seconds;
[325 seconds (vacuum)].

virgair


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Rocket Constructor
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Post    Posted on: Wed Jun 23, 2004 6:35 pm
Do y'all have a specific plan for reducing the cost of insurance for manned flight on your vehicles?

It seems to me that one of the silver linings to doing lots of < 3,500 ft unmanned flights on a smaller vehicle is that reliability and safety can be demonstrated for potential insurers -- they will have numbers for their actuaries to pore over. This is not something of which the expendable launchers have had the benefit.


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Post More answers   Posted on: Wed Jun 23, 2004 9:19 pm
When will we have a manned vehicle:

Well, Russ can climb into the big vehicle any time he wants, but we don’t have any intention of flying a person until we have done many more tests. Our first manned flight will probably be to take the 3000 meter time-to-climb world record, currently held by a Russian fighter jet.

Space counter culture hero:

I don’t feel that we have delivered the results yet to be worthy of the status. We are fighting the good fight, but in the end, results are what matter. We need a bit more time.

Going for it:

I did get all the long lead time items ordered this week. I wish Scaled had a more decisive test flight one way or the other. It looks like they have some issues and a potential performance shortfall, but they also clearly have a working system.

Solid rocket escape system:

No, we aren’t considering it. Having a vehicle free of pyro devices of all kinds is a benefit for the licensing process and adds to ground crew safety. A poorly tested escape system is worse than no escape system at all, because it can actually cause problems as well as fail to do its intended job.

Aerospike engines:

We consider this often, because our low temperature rockets make it a far easier task than for conventional propellants. Its not in our current plans, but we may well give it a try at some point. The primary benefit would be allowing it to operate at very low chamber pressures without flow separation.

Inertial navigation:

We use a Crossbow fiber optic gyro based IMU.

GPS antenna:

It is a standard aircraft antenna, mounted on the top of the vehicle.

One speck in the peroxide and BOOM!:

Really not true. The dangers of 90% peroxide are drastically overstated, and 50% peroxide is pretty darned benign for a rocket propellant. Years ago we did have one tank pop a burst disc with 90% peroxide when we were using the wrong kind of fittings (zinc plated…), but 50% peroxide can tolerate pretty gross contamination with only moderate temperature and pressure increases.

Reentry heat on the engines:

The engines get much hotter from the rocket propellant than they will from a suborbital reentry. Stagnation temperature is only 1400 F or so, and the heat pulse doesn’t last very long. 1/8” thick aluminum won’t melt on a bluff body reentry from 100km. Stainless steel has no problem whatsoever. We do need to make sure the vane actuators are well insulation.

Moon lander:

Sure, we would be interested in making a moon lander.

Pumped engines:

Using a pump allows you to make your vehicle more fragile and complex. We do not consider this a good thing. If we did pursue a pump of any kind, I think Andrew Knight’s rotary cylinder pump is the most promising of the easy-to-fabricate options. The rocket rotor work we did a couple years ago was actually a fairly high pressure pump if you want to look at it that way.

Propellant choices:

Looking at specific impulse as the dominant factor in choosing a rocket propellant is one of the biggest mistakes people make in thinking about rocket engineering. We chose catalytically decomposed monopropellant peroxide because it is the simplest propellant BY FAR to actually make work in a reusable, deeply throttled system.

Hydrazine is a non-starter. It costs over $500 a gallon today, and is carcinogenic. AST is never going to give a launch license to a new manned vehicle using hydrazine. Shuttle / etc are effectively grandfathered in, but don’t expect to ever see a new manned vehicle using it. It doesn’t make sense from an economic point anyway. The same goes for nitrogen tetroxide.

Nitrous oxide has the hassles of a high vapor pressure fluid, lousy bulk density, and it burns fairly hot for the delivered performance. Our mixed monoprop engines would be a much better choice for Space Ship One than a nitrous hybrid. You get basically the same density Isp, but the engine doesn’t burn up each test flight, and you have the option of dumping all the propellant weight if you need to.

Nitric acid is cheap and hypergolic with furfural alcohol, but contrast the little white spot you get on your hands from peroxide that goes away in twenty minutes with the permanent scar you get from anhydrous nitric acid.

LOX is dirt cheap, but it is a cryogen, and you can’t use polyethylene lined tanks. If we weren’t using peroxide we would probably be using lox / alcohol in a regeneratively cooled motor, but we wouldn’t be as far along as we are.

We expect to do upper stage work with 98% peroxide and kerosene.

Insurance:

We hope to demonstrate reliability with lots of test flights, but if the prices are too ridiculous, I might consider self-insuring.


John Carmack


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Post    Posted on: Fri Jun 25, 2004 12:07 am
If Armadillo cuts back to a one man vehicle, will that vehicle be able to compete in the X-Cup?


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Post Other hover   Posted on: Fri Jun 25, 2004 4:43 pm
Your flight control system seems well suited for a ducted fan flying platform. Have you considered a side project like this?


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Post    Posted on: Fri Jun 25, 2004 8:43 pm
Hmm, I thought that the main problem with flying out of White Sands was that they were going to charge you $1 million+ for just a few test flights. That problem could be circumvented just by flying someplace more welcoming. It would make the vehicle less versitle, but you could try using a water-lander untill you get through all the red tape to convert it into a land-based version.

I was finally able to see the boosted hop flight test, and, man, that is incredible. I was stuck for the last two weeks at my relatives' house with only excruciatingly slow dial-up internet, so I waited untill I got back home to my cable modem to watch the flight. When you make future flights to that height again, will you put a camera inside the rocket like you did for the smaller landers? That would be an amazing video. Keep up the good work, guys. :)

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Post    Posted on: Fri Jun 25, 2004 9:10 pm
Senior Von Braun wrote:
When you make future flights to that height again, will you put a camera inside the rocket like you did for the smaller landers?


Yes. We intended to that day too - I had that little camera with me and we'd mounted it on that nosecone before, but we were racing the light late in the day so we decided not to take the time to mount it.


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Post    Posted on: Sun Jun 27, 2004 2:48 pm
Given Spaceshipone's successful yet problematic suborbital flight, is Armadillo Aerospace still trying to win the X Prize?


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Post    Posted on: Mon Jun 28, 2004 2:33 pm
You guys are having trouble getting a launch license. Is there anything your fans can do? Write our Congressmen? Start an online petition? Riot in the streets?

Ok... not that last one.... :lol:

Seriously, anything we can do?


Last edited by Texan on Mon Jun 28, 2004 6:42 pm, edited 1 time in total.



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Post inductive kickback solutions   Posted on: Mon Jun 28, 2004 6:27 pm
Hi John,
I have enjoyed following your teams trials and adventures, Thanks for inviting us all in your adventure.

I was reading your latest log and i saw that you finally got hit with the bain of all systems engineers, inductive kickback. I have had to deal with this problem in most of the electro-machinical designs i deal with both in racecar systems and in computer power control systems. The easy solution for your problem is to attach a fairly large (>5amp constant current rating) silicon diode across each servos limit switchs (be sure and note which half of the drive bridge each switch is on and orient the diode as needed, the diode should not be forward biased during normal operation). This diode will shunt the feedback current when the switch is opened. The servo driver transistors provide this current shunt feature when the driver is turned off by the use of the parasitic diode built into the driver fets (this is a handy feature of the power fets) under normal operation. However when the limit switch is activated the parasitic diode is not in the circuit any more and bingo because the current has no other place to go -->ground bounce. This same inductive kickback is how a automotive coil works to generate the spark voltage needed by the sparkplugs.

I hope that this help,
-Rich


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Launch Director
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Post    Posted on: Tue Jun 29, 2004 11:41 pm
First off, as well as a big thank you for letting everyone know how your project has progressed, I'd just like to say thank you from the bottom of my earthbound heart, Mr. Carmack & friends, for actually DOING it! If I ever make it into space, y'all will be in my will. 8)

Now, for my question:
Have you guys done any number crunching on the feasibility of an upscaled Black Armadillo with H2O2/kerosene as an SSTO? That is, with your engines, same materials, etc..

Or, at least, a stage-and-a-half system with reusable boosters?

Thanks,
Jac

P.S. When you're ready for an X-Prize flight and need some human-weight ballast, send me an email! :P


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Post    Posted on: Wed Jun 30, 2004 12:10 am
<< Hmm, I thought that the main problem with flying out of White Sands was that they were going to charge you $1 million+ for just a few test flights. That problem could be circumvented just by flying someplace more welcoming. It would make the vehicle less versitle, but you could try using a water-lander untill you get through all the red tape to convert it into a land-based version. >>

WSMR is problematical from the standpoint of both cost and red tape, naturally occurring features of all bureaucracies. They are actually quite supportive and have agreed to allow us to undertake manned launches from there - a first for WSMR. However, the cost is prohibitive and given our time frame, now that the X-Prize is all but won, the temptation to wait out the process and launch from a more convenient and less expensive site is appealing. The current legislation in front of the Senate (S1260) , having passed the House overwhelmingly (as HR3752), could open up some interesting possibilities.

<< You guys are having trouble getting a launch license. Is there anything your fans can do? Write our Congressmen? Start an online petition? Riot in the streets? Ok... not that last one.... Texan >>

Ummm, rioting in the streets is probably not in either of our best interests. We do have the advantage in this great democracy of certain leniencies not granted elsewhere - like warning shots - but still not a recommended course of action. Writing your respective senators (those that can read) in support of S1260 could be constructive in some cases.

Unfortunately many Senators are unlikely to support a bill just because their electorate is in favor. The reaction I got from many when trudging the hallowed halls of DC was - What's in if for me and my state? ... Mostly me! Will it get me re-elected? Do you want to make a political donation? If you would like to see politics at its worst go visit the offices of John Kerry, or Ted Kennedy, or Nancy Pelosi, or ... Well, you get the picture. Bloody depressing! On the other hand if you want some upbeat intelligent guys, there are some good people in Congress. T :D alk with Sherwood Boehlert, Dana Rohrabacher, Ralph Hall and their staffers. Straight shooters all.

Neil M
Armadillo Aerospace does not endorse any political candidate or party. We just dislike self-centered, self-serving assholes with a vengeance! :D


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