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Tube construction, Big test facilities, Fire inspectors, DC-X

October 1 and 5, 2002 Meeting Notes

October 1 and 5, 2002 Meeting Notes


Tube Construction


The original tube vehicle that we put together has been completely scrapped without ever flying, we are only using a few sections of it in the new vehicle.  We weren’t confident that the small side firing attitude engines would have sufficient control authority, and we felt the fins were almost certainly going to break off on landing.


The new design uses one of the low pressure (250 psi) 24” diameter Structural tank as a part of the airframe, and has 30 degree half-angle cones for the base and nose.  This is going to be very draggy, but it should be stable and robust.  The propulsion system is almost exactly like the lander’s, with four down firing attitude engines near the inside corners of the tail cone, and a large central engine.  At only 250 psi, that will only be about 500 pounds of lift from the system, and the vehicle will weigh about 300 pounds ready to fly, so it won’t accelerate very hard, but it should be able to fly for quite a while.  We intend to test four large, differentially throttled engines with this platform, which will move the thrust to weight ratio back up to something more rocket-like.


The rocket tower drawn parachute system is almost done, but we are still waiting on some supplies to make a separate little parachute for the tower, which will fly completely away from the vehicle with the parachute free bag.  In theory, the parachute should deploy fast enough to be useful in as little as a hundred feet or so.


Russ found that even our new TIG welder struggles quite a bit welding ¼” thick aluminum plate and tubes together.


We are directly bonding filament wound tube and cone sections to the fiberglass tank, which seems to be working out very nicely.  The parachute loads are going to be fed to the tank through straps, rather than through the airframe, so the bonds shouldn’t be stressed very much


Big Biprop Test Facilities


We finished assembling and water testing our high flow, dual regulated pressurization system that will be used for the 1000lbf biprop.  We built manifolding to be able to gang together multiple nitrogen bottles, but it turns out that a single fresh bottle can flow enough to expel our desired amount of peroxide at 250 psi with minimal pressure drop.  The big Tescom regulators flow a LOT more than the welding regulators we have been using.  Adding a check valve did let the pressure drop during the second test, but that may have been due to the lower supply pressure.  We will probably tax this system when we run the 5k monoprop motor, but we’ll see what it does.  I am still looking for official data on the SCFM flow rates of standard nitrogen bottle valves at various pressures.


We finished the dual motor controller board that we will use to run the valves at the test site, giving us proper on/off control of both peroxide and kerosene valves.  We had been using our old testing system that was designed around solenoids for too long, and the inability to remotely close the valves had forced us to always let the tests run to depletion.  A relay board probably would be appropriate, but we just ganged two batteries together to get enough voltage to run over 250’ of cable.


Fire Inspectors


We had a visit from a pair of fire inspectors on Saturday night.  They were cordial enough, and we showed them everything we are working on, including the video of the flight on Saturday.  They didn’t seem alarmed at our work facility, and the only thing they mentioned was that we should have our nitrogen bottles chained (done), and that we needed a welding permit to have welders on site (we had no idea about that, but will get one next week).


This was a little peculiar, because they said they had a complaint registered on the first, a day when we weren’t doing anything but construction work, and they knew to come by on Saturday night to find us.  There may be some other business around that has people working late that we aren’t aware of, or someone that has seen us for a while got distressed at the sight of the tube vehicle being mocked up, which does look rather more like a missile than our landers.





This is only historically related to our work, but Chris Hanson asked if I would be willing to host a video that he put together nine years ago from the public test flight of the DC-X.  The DC-X was long before my interest in rocketry, but it was certainly an influence on the directions we have been pursuing, and several of the principles from the DC-X team have expressed their support of our work.






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