Thursday, September 24, 2009

Testing Results, mostly good...

For the next 36 days Updates will be short and probably not include much video or pictures, they just take to long to edit and prepare and I'm out of time.

We static tested the silver ball today, on the first static test we were expecting bright orange hydrocarbon flames(We were running gasoline as the fuel) . The exhaust was clear loud and steady. We though the fuel valve did not open and made some minor changes to the static test software refilled with peroxide and ran it again....

During the second run again clear loud steady rocket exhaust, but again no expected orange,
although about 10 seconds from the end of the run there was a noticeable change in the exhaust note.

On closer inspection the fuel tank was empty and there were signs of light soot on the thermal coating in the motor. Based on the run time and amount of fuel we loaded the pitch change at 10 seconds from shutdown would have been when we ran out of fuel. This is the first gasoline fueled motor we've ever seen fired so its possible the only thing wrong was our expectations.

We switched from kero to gas for more volatile fuel and slightly better (1 or 2 sec) ISP.

Given that we then prepared to try a tethered hover with the gimbals, and we ot bitten by small details. On the blue ball the only vent is the emergency vent we fill through the vent and have never had problems. On the silver ball during fueling for the two static tests the purge vent had been open from the main tank utalage to the motor. Before fueling for the potential tethered hover we closed that vent so we could slightly pressurize the vehicle, hang it and see if the roll control thrusters were working correctly. (They were) this caused us to leave the purge vent closed. Since the blue ball has no such vent we did not think it was an issue.
We put the fill tube down the vent with lots of clearance and started pumping.... a minute or so into the fill the hose comes flying back out and sprays everything with peroxide. We immediatly douse the vehicle, and perople with the standby water. This water deluge prevented any real damage, but also caused some of the electronics to be glitchy. So we called it a day and brought the vehicle home to dryout and test the wet parts.

The reason this happened is subtle, the main vent attaches to the tank with a 1.5" Sanitary fitting. A 1.5 inch sanitary fitting is very similar to a 1" sanitary fitting, ie they are identical other than the hole in the middle of the gasket. We had put a 1" gasket on the 1.5" vent. So when the 1" fill tube is shoved down into the vent it seals with this gasket.

Now that I'm home I will review the data in detail and look at the video.


Ben Brockert said...

The SS-67B3 is a peroxide (50%)/gasoline engine, and they claimed that the plume of it was just purple menace.

I'd have to see it to believe it, but there is prior art for the idea that gas/peroxide doesn't make luminous mach diamonds.

David said...

Lean MR might lead to very little visible plume, especially in the desert sun.

David said...

When you static test I assume you have a trust measuring instrument attached to the platform? I would have been interesting to do a mono run to determine the difference as well as judge if it is close to the expected figure.

Having said that - clean exhaust is far better than the alloy engine was able to do - changes to the cat pack?

Paul Breed said...

We have a much better cat pack and much better injectors.