^ Flometrics launched a large liquid fueled rocket in January 2001.

Liquid fueled rockets are a good way to hone your engineering skills and the dream is that launch costs will be low, if you can recover it undamaged. This one worked. We setup a valve system with a guaranteed LOX lead. The LOX valve was opened by an air solenoid which was pressurized by a solenoid in the Ground Support Equipment (GSE) When the LOX valve achieved the full open position, it operated an air switch, which in turn operated the solenoid for the fuel valve. This gave us about 1/3 of a second of LOX lead which prevented a detonable mixture from forming in the combustion chamber (apparently). Two sets of pneumatically actuated valves were used in the lower part of the rocket. The first set operated the fuel and LOX valves. These were staged as mentioned above, and the air pressure to close and open them was provided by quick disconnect air hoses connected to the GSE. There was also an air hose which actuated the other set of valves to vent the tanks. The closing of the vents was via a port on the side of the rocket. The basic launch sequence with respect to the valves was as follows: Fill fuel, LOX and Helium in the event of trouble, vent tanks.

If you listen carefully to the video you can hear the air valves pop right before the ignition.

The high pressure Helium disconnect is via a small air cylinder which pushes the sleeve on a pneumatic disconnect backwards. (Thanks Dave C.) The pneumatic control lines disconnect automatically when the rocket takes off because their sleeves are connected to a stake in the ground. Each line is covered with a Teflon sleeve so that they won't get stuck. There are no electronic wires leading from the GSE to the rocket. The tanks are pressurized with a small composite helium cylinder. This cylinder was originally used to deploy a slide on a 747. Each of the tanks is made from a pressurized water fire extinguisher. A fitting is welded into the top to pressurize and vent the tank. We made an injector plate which was a duplicate of an original one.

One side of the combustion chamber was indented. This may have been due to the impact with the ground. Unfortunately the recovery system did not work as well as the vehicle.

See the videos of the launch below:

• Rocket close.avi
• Rocketfar.avi

< Impact ( 81 KB) The nose of the rocket was 3 feet underground. There was a burn time of 6-7 seconds. We don't know how far up it went, but it disappeared from view for a few seconds.

< Inside ( 36 KB) We were a little bit cold that morning.

< The Crew ( 37 KB) The team, including Mike, who made the injector plate from Bruce's reproduction of an orginal 1958 Rocketdyne design

< Family ( 22 KB) The Jetsons

We are going to try again, but it is somewhat expensive:

Details of the earlier attempt

We attempted liftoff on Dec. 2 and 3 in the Mojave desert near Randsburg. On the first attempt, our ignitor failed and we dumped 3 gal of LOX and jet fuel on the ground. (Lesson #1: Do not let your ignitor sit in the toolbox for a year near the beach) Then we refueled, but the main valve would not shut due to a broken pneumatic fitting. We guessed that the plastic hose barb might have failed due to the cold as it was near the LOX tank.

We fixed the fitting and insulated it from the LOX and tried again, but the fitting broke again because the insulation got in the way. We took the rocket down and fixed the pneumatic lines with a late night run to Home Depot (lesson #2: Do not use plastic tubing or fittings).

These attempts allowed jet fuel to get in the LOX side of the engine, so we cleaned out everything and tried to launch a third time on Sunday. On the third attempt the engine blew up due to a drop of jet fuel in a LOX fitting leading to the engine. (Lesson #3: Do not make fittings with places where contaminants can hide in oxygen systems.)

Another good lesson we have learned is that if you want to use ball valves for LOX, you should not use valves where the ball is made of a different material than the housing. (They get really sticky at low temperatures.) Also, ice crystals are harder than steel at LOX temperature and any condensation makes the valves hard to close and scratches the ball.

Images of the explosion:

< Looking Good ( 35 KB) The rocket before the explosion.

< Initial Explosion ( 53 KB) Carl took this picture just as the engine blew up. Spectacular!

< Kentucky Fried Rocket ( 33 KB) The flames look bad but mostly just the fins and the skin burned.

< Burned Aluminum ( 34 KB) Dave Crissali pointed out that the explosion started in this fitting. Some of the aluminum was consumed in the fire.

< Going Home ( 30 KB) The burned up rocket on top of the station weapon. (The weapon is for sale.)

< After the explosion ( 87 KB) Hey I think that air cylinder is still good...

We plan to try again in January because the damage is not that extensive.

Original Rocket Specifications:

• Liquid fueled LOX and Kerosene Flow rate 25 gpm
• LOX 15 GPM Kerosene (Jet A)
• Engine: Surplus Rocketdyne LR-101, 1000 lb thrust
• Fully fueled weight: 150 LB
• Burn Time: 7 sec
• Projected max altitude: 11,000 ft
• Recovery: Altacc altimeter from Blacksky
• Parachutes from www.americanarmynavy.com surplus

Below is a simulation result for the flight (Rocksim).

More pictures:

< Rocket Schematic ( 16 KB) Shows how the valves and regulators supply pressurized helium to the fuel and LOX tanks.

< Assembled Rocket ( 60 KB) Before the paint went on in front of Flometrics.

< Upper Compartment ( 28 KB) This contains the high pressure helium bottle and regulators, and the pneumatic cylinders and valves that deploy the parachutes. The pipes contain the pressurized air to deploy the parachutes.

< Center Compartment ( 115 KB) Contains the LOX and fuel tank and the fuel vent. Both tanks can be vented remotely in case the rocket does not start properly. A set of pneumatic hose connections is used to remotely activate the main fuel and LOX valves and vent the tank.

< Lower Compartment ( 25 KB) Contains the LOX tank. The tank is insulated so that not too much of the LOX evaporates while we are pressurizing the system. Note that the fins are a little large. But they look cool, and we are not trying to get to the moon.

< Main Valve ( 22 KB) This valve did not work very well at low temperatures. Furthermore it turns on both the fuel and the LOX at the same time. It would be better to turn on the LOX about .2 second before the fuel so that a detonable mixture does not form in the combustion chamber. When the LOX is turned on first the combustion chamber is cold at start up so the jet fuel does not vaporize too much. If there is too much well atomized, premixed LOX and Jet A then the chances for a hard start are much greater.

< Parachutes ( 48 KB) That's right the parachutes are packed in Tupperware bread boxes. First a small drogue chute gets pulled out as the air cylinders push off the nose cone. Then at about 500 ft agl, the main comes out and gently drops it to the ground.

< Cryo Test ( 31 KB) The valves were tested with Liquid Nitrogen. They were a bit sticky at low temperature and they got stickier when we tried to launch

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