We met at Norwood Autocraft, and actually got everything all
plumbed together, and were able to load and flow water through the engine on
the test stand (without the catalyst bed). I need to start bringing a
digital camera to the meetings, because it looked pretty cool all set up.
Bob Norwood was a huge help, and he is interested in working
more with the project. Building things at his shop is a very large benefit.
It was a bit sobering to see that something that takes a
couple minutes to draw out on a whiteboard takes three hours to put together at
a fully equipped shop. If we hadn't been at Bob's shop, it probably would
have taken us three weeks of ordering a couple new parts each week before we
got everything together.
Bob also had some strange metallic foam that had been used
as a catalyst base in peroxide dragsters a long time ago. We may want to
do some tests with that, depending on how well the pure silver screens work.
The screens in Juan's motor appear to be silver plated
brass. We will get more exact documentation before we run anything
through the motor.
I did a radio-shack switch box for the fill cart valve
controls, and Russ and Phil wired it up. A Good Call on their part was to
use different connectors for each valve type, so it isn't possible to connect
the switches to the wrong valves.
I showed my current primitive 3D GPS trace visualization
program on my laptop.
The flight hardware (which was strapped to the test stand)
|-- manual bottle valve -- launch valve -- engine
|-- Quick connect to fill cart
|-- Tank pressure guage
|-- Tank blow-off
The tank manifold is not very optimal, but it is fairly
convenient for our current purposes. Both the manual bottle valve and the
launch valve are fairly restrictive, so we may need to run higher tank pressure
than would be necessary on a better system. We have plenty of headroom
for pressure with the current tank.
When we get around to mass and flow optimizing a flight
vehicle, we will probably get a custom tank manifold made that has a direct
shot at the flight valve, and only one side port for the fill connector.
It turns out that a pipe clamp holds the engine to the fill
stand quite nicely. If we put a 90 degree bend on the inlet, it should be
able to push against the load cell without any problem.
The fill hardware (which was spread out on a table for now)
A short length of high pressure hose.
|-- N2 solenoid - high pressure hose - N2 regulator - N2
|-- H2O2 solenoid - <check valve< -- low pressure hose
- H2O2 tank
|-- Vacuum / purge toggle valve - low pressure hose - vacuum
The N2 solenoid and the H2O2 solenoid are momentary valves
controlled by a single dual throw momentary switch on the launch panel.
There is never a reason during the fill procedure to blow N2 through the H2O2
fill tank, so it was good to make it impossible.
The Vacuum / purge valve and the launch valve are open /
close valves that retain their position without power. This allows us to
make sure that both the flight hardware and the fill hardware are never left
closed, where they might pressurize from residual peroxide decomposition.
There are several things we are going to improve on the
We intended to have a catch tank before the vacuum pump, but
we didn't have the bottle for it. This will be mandatory to prevent
blowing anything into the vacuum pump. We would also mount a vacuum gauge
on the catch tank, and it should have a one-way vent on it to make sure that it
never gets pressurized.
We found out that we positively need a check valve before
the engine. I had been thinking that it was a good safety idea, but it
turns out to be more crucial than that, because the launch valve is pretty directional,
and leaks when there is a vacuum in the tank. We did our test with Phil
holding his hand over the engine nozzle (and getting a bit of a welt from it)
while we drew the vacuum and loaded the water. We managed to not hear
Neil making the sensible suggestion of just temporarily closing the manual
We might as well add a check valve to the N2 solenoid as
well, although there wasn't a functional need for it. I have a couple
coming with the plumbing order this week, so we should be able to use
those. The check valve on the H2O2 solenoid still doesn't have a spring
in it at all. It can't be very strong, or it will prevent the vacuum from
drawing the peroxide through it, but we probably want at least a tiny amount of
force to make sure it seats properly.
Our peroxide (water) transfer tank was just a jug with a
siphon line dropped in it, but I want us to make a bottom-draining tank for it.
I still have some concern about the current arrangement
leaving peroxide in the high pressure hose going to the quick connect. It
would be ideal if we could just be rid of the hose, and have all the fill
valves plug right onto the quick connect, but that is probably too much
shearing weight for it. If we need the hose, we should arrange for the valve
manifold to be suspended above the quick connect, rather than below it.
We may want to have some kind of flexible supporting arm on the fill cart that
can bear the weight while it is connected. We need a good enough solution
that will work for both the test stand and the launch pad.
The little solenoids get pretty hot while they are
operating. We may want to experiment with adding some resistors in line
with them. The peroxide solenoid won't have to open against any pressure,
although it must stay closed when the fill manifold is pressurized. It
may not be an issue once we get a bottom draining tank and aren't screwing
around with keeping the siphon line off the wall.
We have a pressure gauge visible on the flight tank when it
is on the test stand, but we won't be able to see that when it is in a
rocket. We could add one to the fill system, or we could just rely on the
regulator gauge from the N2 bottle.
We were still using the AC vacuum pump. I mounted a
switch on the fill controller for a pump control, but we still don't have a 12V
The first time we pressurized the system, we were leaking
all over the place. We weren't sure before, but it turns out that both types of
valves really do need to be installed with high pressure on only one
side. They don't seal backwards.
The quick-disconnect works extremely well under high
pressure, with no drips or spurts.
Phil suggested an additional safety switch for the N2
solenoid in addition to the momentary actuator.
The nylon fill line we had going into the water tank kept
sucking itself to the wall during loading. If we don't get a good bottom
draining tank for peroxide / water loading, we should cut notches out of the
end of the siphon line so it can't seal itself to a flat surface.
We pressurized to 400 psi.
We didn't have a switch box for the launch valve (which is
intended to be a separate box from the fill cart control panel), so we just
tapped a power jumper directly to the open leads.
We were all set for a water-rocket like jet out the engine
nozzle, and were disappointed when the water mostly just flowed out the bottom
of the nozzle. We then remembered that the front catalyst retainer was
fixed in place, so the water didn't have a direct spray exit. If we want
a jet next time, we will disconnect the line from the motor.
All in all, it was an extremely good night.
Here is the full fill procedure:
Check N2 bottle for sufficient pressure to fill the engine
Set the vacuum / purge valve to open.
Nothing should happen, the port should have been left open.
If it had been left closed, there might be a venting of N2
Set the vacuum / purge valve to closed.
Just in case the engine tank was accidentally left
Connect fill cart to engine fill port.
Set the vacuum / purge port to open.
If there was anything in the engine tank (there shouldn't
be!), it will purge.
Set the launch valve to closed.
Needed before we fill the tank. It should have been
Start the vacuum pump.
Wait for the desired vacuum level.
Set the vacuum / purge valve to closed.
Stop the vacuum pump.
Hold the H2O2 valve open until it is all sucked into the
Hold the N2 valve open until the flight tank is pressurized.
Disconnect the fill cart from the engine fill port.
Set the vacuum / purge valve to open, relieving the N2
pressure in the manifold and safing it for any H2O2 decomposition.
We need to get all the improvements into the fill system,
get it all secured into it's own cart, then practice and polish the filling
checklist until we consistently do it without spilling a drop of water.
We also need to practice purges as well as engine firings.
We need to do peroxide compatibility checks. We may
have some synthetic rubber in the solenoids that need to be replaced. We
can run some lower concentration peroxide through the system a few times before
trying the concentrated stuff.
We only have a small quantity of concentrated peroxide left,
but we will probably run it through the engine to get a short, but gratifying
blast of steam.
A bunch of Earl's plumbing fittings, hoses, and accessories
will be here by next week.
A bunch of radio and telemetry stuff should be here by next
The heavier load cells are still on order.
The silver screens are still on order.
I have handed off the FMC 90% contact to Russ. We may
have a sire inspection before next week.
Russ or Phil should pick up some stabilized 70% for the
hybrid test track, in case we have a delay with the 90%.
Did the safety equipment get ordered yet? Before we
touch even the lower concentration peroxide in the fill system, I want everyone
wearing at least goggles and gloves.
I'll pick up another little project box and materials for our
launch valve controller. I'll go ahead and get a long spool of wire for
it, so it will be appropriate for launching as well as static testing.
How far away do you think we should be for the launch? I will try it with
straight wiring first, but we might need a relay system if we have an extremely
We could either make the launch valve controller
self-contained with it's own batteries (probably one or two RC car batteries),
or require the launch valve controller to be hooked up to the battery on the
fill cart. I hate having multiple batteries, but it is probably better to
remove the temptation of opening the launch valve on the test stand while the
fill cart is beside the engine.