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May 1, 2001 Meeting Notes

May 1, 2001 Meeting Notes


In attendance (the whole crew!):


John Carmack

Russ Blink

Phil Eaton

Neil Milburn

Darin Smith

Bob Norwood


New supplies:


8 each of all NPT to –3, -4, and –6 male/male adapters in aluminum

Two stainless steel quick connects with five plugs

20 pounds of stainless steel pipe fittings (four of every combination of 1/8, ¼, and ½, plus Ts and 90s)


On order:


-6 aluminum speed flex hose ends

Stainless ¼” needle valve

Mil-spec aircraft electrical supplies

Pilot headsets for piloted VTVL

Extra burst discs


To get:


Full complement of AN fittings in aluminum to replace some of the steel ones

150 psi tank

Various 150 psi plastic fittings and hose

150 psi solenoids

Pressure gauge

Vacuum gauge

More big solenoids

Hearing protection

Tank pressure transducer

Tank temperature transducer

Russ: Fill both nitrogen bottles

Russ: Fill welder argon bottle

Russ: Foam blocks for VTVL from your local foam supplier

Phil: Charge all the batteries

Phil: Pick up more tables

Phil: 70% food grade peroxide

Neil: 6” of hard line for pressure transducer. One side female ¼” NPT, the other side ideally male 1/8” NPT, but we can adapt

Neil: 1000+ psi nitrogen regulator



Space Access


I spent three days at Space Access ’01 last week, and gave the first public presentation of our work. Jess Sponable, who was the director of the DC-X program, gave our direction his seal of approval after my talk.


An interesting bit was that XCOR’s 15 pound biprop thruster, which was fired at the hotel, was far louder than I expected. It was at least twice as loud as all four of our 15 pound engines running together on the VTVL, which fits with noise scaling by the third power of exhaust velocity.



New Suppliers


We got a quote for burst discs to our specification from www.bsbsafetysystems.com -- $338 each! Phil is talking to another company about getting something reasonably close that is in mass production.


This company sells fiber optic gyro demonstrator kits (single axis) in two different quality grades for $1500 and $2500:



I may wind up getting a couple of these when we want to do high G launches.



Work Today


We rebuilt everything in our plumbing system with all stainless steel fittings and aluminum hose ends. After the cook-off last week, we aren’t going to use any brass or non-stainless steel anywhere in the system, even if it shouldn’t have peroxide sitting on it. We have two bits left: the bottle valve adapter is plated steel, and the vacuum hose barb is brass. We should probably just move to a custom machined aluminum four port bottle manifold for the test stand like we have on the VTVL, except with bigger ports (1/4”


Russ and Phil welded a stand on the fill cart for the solenoid control and screwed the solenoids to the mounting bracket. It is amazing how much this cleaned up the cart. There are still a few things to add to the fill cart:


Checklist mounted next to the control box.

Cradle for nitrogen tank.

Something to secure the water jug hose holder.



We water tested a couple times to get the new plumbing leak free.


We finally ran Juan Lozano’s engine. It was designed as a 100lb thrust engine, but we weren’t expecting to be able to flow enough peroxide through our current solenoid to see that much thrust.


We used 425 ml of 98% + 75 ml of distilled water in each test.


We ran it once at 450 psi, and again at around 410 (our nitrogen bottle was running out). It made a bit over 50 pounds of thrust. We considered plumbing up our big manual ball valve to the engine so we could give it full peroxide flow, but we couldn’t think of a safe and sure enough way to actuate it, so we sensibly put it off. We will probably try two ganged solenoids next week.


His catalyst pack seems to work fine, with a very short warm up time. I am going to inquire about getting one of his new packs that is supposed to survive with 98% peroxide for testing.




We ran into a few issues during the testing:


Our bottle pressure gauge was killed by the cook-off last week. The one on the VTVL still works, but I’ll pick up another one.


The new stainless steel quick connect we installed couldn’t be popped off when at the full 450 psi pressure, although it could at 200 psi.. We just left the fill cart connected to the test stand during the firings, but we need to be able to remove it for the VTVL. The old steel ones we used had a lever on them, so they popped right off. We may try welding some bars to the connector, but I will look for more connectors.


The solenoid driving battery ran out just as we were about to test. I had done a couple water runs and dry runs, but when I fired the engine for real, nothing happened. We hooked another battery up, but that did involve approaching the test stand. In the future, we should have a long coil of wire from the solenoid going around the corner to the actuation electronics, instead of having them out by the test stand.



We hashed out the redesign of the VTVL tonight. Bob is going to tack it together this week, and we will check it out on Saturday.


We are going to investigate duplicating the VTVL with 150 psi components. The Isp will suffer due to very small expansion ratios, and the engines will need to have bigger throats, but all the plumbing can be done in plastic, avoiding corrosion entirely.


A list of peroxide / material reactions is available at:




Notably, nylon and Delrin have “severe effects”, which precludes several classes of fittings and hose.



We are also going to look at the other extreme – running the current tanks at 1000 psi.





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