back to article Vulture 2 rocket motor heater a non-sizzling success

The Low Orbit Helium Assisted Navigator (LOHAN) team is toasting a toasty success today after reviewing the data from our recent Judy test flight, which carried the rocket motor heater rig designed to stop our Vulture 2 spaceplane's mighty thruster from catching a nasty cold. Here's the data in question, captured as Judy rose to …

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Boffin

How about...

Sticky backed copper tape patches,(garden centre slug repellent type,) mounted on the fuselage, with springy copper feeds from your battery resting thereon? Virtually zero friction or resistance to sliding, and should easily handle the low current draw.

I can do you a drawing, but I hope you don't need one.

Crack on chaps.

:o)

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Bronze badge

Re: How about...

Isn't LOHAN going to be free to swivel around the Flying Truss pole though? Might have trouble keeping the springy copper feeds you speak of on the target patches of copper tape.

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Bronze badge

Re: How about...

Small magnets stuck to the back of the truss-side contacts, small bits of iron stuck to the back the Lohan-side contacts; said small bits of iron being snipped to minimum size and weight that would provide enough contact force (or is that already covered by Apple patents).

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Silver badge
Coat

Re: How about...

"Might have trouble keeping the springy copper feeds you speak of on the target "

The Playmonaut pilot just needs to hop out with a wooden pole and reattach the pantograph to the overhead wires. (You young'uns won't get this reference)

Coat. 'Cos it's cold outside the cockpit.

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Silver badge
Coat

Re: How about...

The Playmonaut pilot just needs to hop out with a wooden pole and reattach the pantograph to the overhead wires. (You young'uns won't get this reference)

You would be surprised.

Mine's the one with the World Of The Children volumes in the pockets. They're bloody big pockets.

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Re: How about...

Similar idea with contact pads on the fuselage (copper or brass, slightly convex surfaces to enable clean breakaway) but using lightly sprung carbon motor brushes as the contact from the battery supply / truss assembly? The brushes could be shaped to ensure good electrical contact.

If it works for motor armatures it may work here, the graphite from the brushes would provide some lubrication again to ensure clean breakaway.

Just a thought.............

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Bronze badge

Re: How about...

if you are worried about wobble disconnecting sliding contacts why not make them rings (or parts of an arc) wrapping around the mighty rocketship. if there is wobble, the contacts just slide around the long axis but stay connected.

[was going to ask my brother who did actual rocket science but he already feels too superior]

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Bronze badge

A quick question, and a thought

You took the temperature logger down to "between -50 to -60°C." which I assume is outside it's operational expectations at which point any temperature reading must be a tad suspect.

Assuming you are not using a full PID temperature controller because of cost or weight, why not try splitting the heating into two elements (no pun intended) a small heater that can deliver a constant trickle of heat and a larger one under thermostat control?

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Silver badge

Re: A quick question, and a thought

Because the area in contact with the constant trickle part will get really very hot and melty, as there is not enough air to move heat away at that altitude.

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Me?

Heater off?

I do not understand how the inside of the motor can drop to -11 if the case is at +50.

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Re: Heater off?

The "(fireproof) nylon wadding, to simulate the presence of the motor APCP reload." either doesn't simulate the APCP well (is less conductive than the rocket fuel) or does simulate the APCP well (it's not that conductive a material. )

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Bronze badge

Mangle an old electric toothbrush

They charge the battery via a transformer in the base, and it should be possible to get two or three watts through this with reasonably efficiency. Such toothbrushes lift off their stand easily enough.

To measure the temperature a non-contact thermostat can be rigged up with an LED/photodetector pair and a small mirror on a bi-metal strip, perhaps also using a couple of lengths of fibre-optic to allow the electronic bits to stay inside where it's warm.

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Magnets...but with a difference

Magnets to attach the power wires.

Yes they have been suggested and found to be too strong to just pull off but...don't just arrange for them to direct pull.

Magnets are strong close up, but the pull drops off rapidly so only small motion is needed. Thus arrange for the lead wires to run along a lever so that the force to pull the connections is minute.

Keep the wires and levers lightweight but stiff (carbon fiber etc.) so they don't contribute significant force on t6he magnets during jiggling.

---------------------------------------- rear face of rocket

..........................O

_____________O__V_

(

)

Key: (=wire. _ = lever O=magnet pair with contacts between V=fulcrum fixed to rocket ....=space so the ascii art works.

At rest, there is a small gap between the lever and the fulcrum point. As the rocket starts to move, the feed wire tensions, loads the lever that can rock until the fulcrum makes contact and the magnet is popped apart and hangs free. The end of the lever could even strike a tag fixed to the flying truss instead of loading the wires.

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-50C on the outside but +50C on the inside

Looking at the graph it's just a funny coincidence that it cut out with an inside temp of +50C when the outside temp was also likely to be around -50C. It's strange how things work out.

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Magnesium wire run behind the motor

[See subject]

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Not a digital solution

I realize that analog is so passe... but a much simpler solution for a temp controller would be to use an LM34 three pin temperature sensor input to an LM10 combo op-amp and precision reference. Basic circuit is in the LM34 data sheet. Set desired minimum temp on controller, heat goes on at that temp, goes off anywhere above set point. Parts cost under $10 US. Want degrees C instead of Degrees F? LM35.

Doc

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