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Week of Oct-4 meeting notes and updates:

 

Misc

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I have my technician ham radio license now (KD5LUY), so I am going to pick up some two meter handheld radios for the telemetry soon.  If there is a better band for it, someone let me know.  Transmitting telemetry over the family radio handheld systems I have isn't technically legal.

 

Darin brought the accelerometers, but we don't have circuits for them yet. He will be looking into the eval boards, or just building it from scratch.

 

I talked to FMC again about the 90%.  They have it available right now, but they will have to do the site inspection before they will let us buy it. They are going to want to see the following things at our facility:  good supply of water, clean siphons or pumps for transfer, a safety shower, good ventilation, and disposal plans.   Russ, you may need to take point on getting that done at your site.  The FMC guy may be up here next week for other work, so we will probably meet with him even if we don't have everything in place yet.

 

Russ confirmed the silver screen order from the Indian company, but we don't have a delivery date yet.

 

Phil brought in a big rocket that could hold our flight tank.  It is still open for discussion whether we are going to modify one of Phil or Neil's rockets or build one from scratch for the peroxide motor.

 

Neil: if you sent the valve catalog person to the address on my business card, that was our old building.  See if you can grab a few catalogs for the next meeting.



Valves

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I brought in two NOS valves for us to experiment with.  Both valves are in the $100 to $200 range, each.

 

The cheater solenoid is a normally closed solenoid that draws 7 amps at 12v.

 

The remote bottle valve is a switched valve that can be rapidly set open or closed, and stays that way without any further power.

 

The not-very-scientific test of blowing through the valves showed the RBV to be noticeably more restrictive than the solenoid, as well as heavier.

 

We discussed using the solenoid for the launch valve by including a small battery pack with the rocket, but it was considered important to make sure that the tank stays vented after the flight.  The solenoid would draw the battery down fairly quickly, then leave the tank closed.  If there was residual peroxide that got at all contaminated, the tank could pressurize if we didn't get to the rocket quickly.

 

Until proven unworkable, the plan is to use the remote bottle valve as our launch valve on the engine.  The three wires will be connected to exposed lugs on the outside of the rocket, which will be connected to our launch system with alligator clips.  We can pulse the valve open and closed to warm the catalyst pack before the full power launch.

 

I also brought a handful of braided stainless teflon hoses and fittings from Earl's.  The braids are a bit of a pain to work with, and I am wondering if we can just use the teflon core in cases where we aren't worried about hose damage.  Does anyone know if the braid's strength contributes to the line pressure rating, or is it all from the hose?

 

I still don't fully get the reasoning behind which fittings are AN, pipe, or CG.

 

Engine

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We pulled apart the engine we got from Juan.  It is a nice looking piece of work.

 

Interestingly, the catalyst pack is not just pure silver screens, but includes some other types of screens at the entry side, and interspersed through the pack.  Possibly getting the peroxide flowing into the screen pack before it touches any catalyst is a good thing.

 

We haven't had a check valve between the launch valve and engine in any of our previous discussions.  With the engine below the tank, a check valve is needed to prevent an overpressurizing chamber from blowing back into the tank and draining more peroxide in.  That could happen if we had a very undersized nozzle, and would be "bad".  On the VTVL platform with the engines above the tank level, there wouldn't be any drain/siphon effect, but it would probably still be a good idea.

 

Both valves are straight through flow.  The current bottle manifold has a 90-degree outlet, but if we machine our own bottle connector, we could rigidly connect the tank to the T for the fill valve to the launch valve to the check valve to the engine.  The current manifold is nice for the test stand with the manual valve, pressure gauge, and blow-off valve, but it would be dead weight in the rocket, and would require some flexible line going from the bottle outlet to get back in the centerline.

 

We need to make some brackets to hold the motor on the test stand.

 

Fill Cart

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Resolved:  the vacuum catch tank should be large enough to serve as the purge tank. It will take longer to draw the vacuum, but it avoids a possible fuck-up scenario of someone accidentally overflowing the catch tank by dumping the entire flight tank into it, and it saves us extra valves and lines for a dedicated purge system.

 

We hadn't addressed this in previous discussions, but we need to make sure that none of fill system is ever left in a closed position.  The decision was to make the vacuum / purge valve an open/close valve instead of a momentary, and add an explicit purge step to the fill checklist after disconnecting from the flight tank.

 

Resolved: don't worry about plumbing a second nitrogen tank in the fill cart to handle a tank running out with the engine not fully pressurized, instead add a check of the bottle pressure to the checklist before hooking it up to the engine.

 

The mil-spec quick connect fitting was very cool, and should work out great for the fill connection.  We have a couple, but we don't know exactly where we could get more.

 

If we can only find a 400psi nitrogen regulator right now, we can live with it, but we will eventually want 1000psi capability for testing.

 

The vacuum source is an open question right now.  The existing vacuum pump works fine, but requires a lot of AC power.  Various options were discussed.

 

 Idea: can one of those little cigarette lighter powered tire pumps be cannibalized into a vacuum pump?

 

Parts list:

 

Cart to hold everything

12V car battery for power

Water bucket with lid

Quick connect

Four port manifold  (quick connect, vacuum, peroxide, nitrogen)

Nitrogen check valve

Nitrogen line

Nitrogen bottle

Nitrogen solenoid

Momentary pushbutton for nitrogen solenoid.

Nitrogen regulator

Peroxide check valve (very soft spring for vacuum draw loading)

Peroxide line

Peroxide solenoid

Momentary pushbutton for peroxide solenoid.

Peroxide transfer tank

Vacuum line

Vacuum catch tank (five gallon water jug)

Vacuum pump

Vacuum gauge for catch tank

Vacuum solenoid (use remote bottle valve so it can be left open)

Two position momentary switch for bottle valve.

 

We might share the check valves by teeing the peroxide and nitrogen lines

 

It would be best to have the nitrogen and vacuum valves right at the filling manifold to minimize the chance of any peroxide draining into the lines during filling, but the solenoids are too heavy to just hang off the quick connect.  We might want to consider some semi-rigid support for it.

 

When we go to a flight tank without a pressure gauge, we will need a pressure gauge on the fill manifold.  We may just take the one off the flight tank.

 

The game plan

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Next week we should complete the fill cart, and we should get several practice runs loading and blowing water through the engine on the test stand (without the catalyst pack). That might even register a bit on the load cell.  If all is right with the universe, we may even blow our remaining concentrated peroxide through the engine for a short bit of thrust.

 

We should plan on several short runs, and several full flight load runs on the test stand once we have our drum of 90%.

 

We need to prepare the peroxide rocket.  What electronics do we want to run?  Probably an off-the-shelf altimeter for recovery, but we can also include my GPS telemetry system and Darin's accelerometer systems.  We need our own big launch rail.

 

We can test several things at the HPR launch this month.  I should have my GPS telemetry system (If I don't have the telemetry working yet, I'll just log the data to a basic stamp for analysis), and it would be nice if we could fly the experimental rocket on a certified motor before we try it with the peroxide motor.  It might even make sense to launch it with the flight tank filled with water to more closely simulate the flight conditions.

 

Get the waiver for an experimental launch in November and fly the peroxide rocket a few times.  If we have done everything right, we should be able to just put it back on the rail, roll the fill cart up to it, and run through the fill procedure to get it ready for flying again.

 

An interesting thought: a later "smart" rocket with a micro controller and some more valves could use residual tank pressure to do parachute ejection.  After the peroxide has blown out, it could close it's launch valve to retain the nitrogen pressure.  When it wants to eject the parachute, it could open a different solenoid to vent the nitrogen behind an ejection piston.   Peroxide drips might be a problem, and it might just be simpler and safer to have a separate little cold gas tank for ejection, but it would definitely be nice to get rid of the black powder ejection charge.

 

Another "smart" option would be to experiment with optimal engine thrust curves instead of just snapping to wide open and staying there.

 

Post launch, the effort will turn towards the VTVL platform.

 

Testing pulse-width modulation of engine solenoids and searching for better computer controllable proportioning valves.  Russ is checking on the electronics needed to switch the solenoids with a logic level input.

 

Building engines from scratch.  We may build some 100-300 lb thrust motors that we could launch the big rocket with, but my push is to figure out the motors we will use for the VTVL system.  Those will probably only be 10-20 lb motors, because there will be four of them on the vehicle, and we don't want it to generate much more thrust than the platform weighs, since we will be targeting tethered hovering and control behavior.

 

Building the VTVL platform.  The current idea is to use an inner tube as "landing gear" (later untethered flights may launch from water), and have the four little engines spread high and far, so the exhaust plumes are as far from the ground and body as we can manage.

 

We will see how controllable it is with a purely manual joystick and throttle interfaces, but before we untether it we will want gyros and range sensors giving good instrumentation, and possible an auto-pilot.

 





 






 
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