back to article Cunning Reg reader cracks LOHAN hot coupling condundrum

We invite fans of our Low Orbit Helium Assisted Navigator (LOHAN) project to raise a glass or two today to the Reg reader who finally cracked the problem of just how to hook up our Vulture 2 spaceplanes's rocket motor heater. To summarise, we've got a space-grade Polyimide Thermofoil flexible heater wrapped round our aircraft' …

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  1. Mark 85 Silver badge
    Pint

    Truly a KISS moment

    Simple and efficient it is. Have one and celebrate. ------------->

  2. Anonymous Coward
    Anonymous Coward

    Icing on the cake...

    ...would be if this idea came to him while he was contemplating the meaning of life in his shed.

  3. Anonymous Coward
    Anonymous Coward

    Weight

    Isn't this plane looking a little heavy?

    Will there be some test flights of the actual spaceplane before the big launch?

    Not really related to this specific item, which is probably as lightweight as you'll get.

    1. Gordon 10 Silver badge
      Thumb Up

      Re: Weight

      I asked that in a previous comments section. How heavy is the plane these days? Whats the lift calculation?

      1. Lester Haines (Written by Reg staff) Gold badge

        Re: Re: Weight

        We're just wrapping the final attachment of the canards and putting in the last few avionics bits, then we'll have a figure.

  4. hammarbtyp Silver badge

    Testring?

    I am assuming that it will be tested at operational high altitude temperatures to ensure that the release friction will be consistent?

    1. Lester Haines (Written by Reg staff) Gold badge

      Re: Testring?

      Yes, we can give the system a freeze test. Some of our ultra-low temp grease might be of use, but we'd have to check its conductivity.

      1. Vladimir Plouzhnikov

        Re: Testring?

        Maybe graphite-based lube like ROCOL 210 would be suitable or CW7100 silver-filled grease...

        There is also an issue of different heat expansion coefficients if the wires and the tube are made of different metals.

    2. Martin Budden Bronze badge
      Headmaster

      Re: Testring?

      Did you test the word "testring" with a spell-checker?

  5. chizz

    Why not use...

    ... pogo pins, as per any test fixture.

    first thing that popped in my head

  6. Arachnoid

    Just a further suggestion

    Could you not use thin strips of sticky metallic tape for the break point, it would provide good continuity between the tubes and the cabling but still have the ability to shear off cleanly on launch?

    Alternately a reverse cloths peg style of clip that provided the connection onto the inside of the tube by sprung assisted friction alone and the thrust would again draw the clips out of the tube.

  7. Anonymous Coward
    Anonymous Coward

    Re. pogo pins

    Sounds good.

    I wondered about simply using a piece of 70C alloy, similar to Chipquik (tm) but with slightly less indium so it doesen't go brittle at low temperatures.

    Only thing I'd do is add triple redundant contacts so if any two things break the failsafe still operates.

    ie physically separate contacts encased in heatshrink to avoid shorting.

    1. b166er

      Re: Re. pogo pins

      Magnets?

      1. Anonymous Coward
        Anonymous Coward

        Re: Re. pogo pins

        > Magnets?

        How do they work?

        1. Arachnoid

          > Magnets? How do they work?

          https://www.youtube.com/watch?v=OvmvxAcT_Yc

  8. 4ecks

    What is the voltage + current

    expected to go through these connectors? You don't want hot-spots welding them together, low temperature conductive grease sounds like a good idea.

    1. Lester Haines (Written by Reg staff) Gold badge

      Re: What is the voltage + current

      12V, 2.24W. Yes, some grease is in order, and will be on order when I find a suitable product.

  9. Dave 32
    Thumb Up

    Conductive Grease

    The conductive grease sounds like a good idea. Note that Copper oxidizes, producing Copper Oxide (I or II), which is either non-conductive, or a semiconductor. The conductive grease should prevent the oxidation. One could also get fancy and Silver plate the interior of the Copper tubes (Silver Oxide is a conductor); consider some of the electroless Silver plating solutions, which will deposit a few Angstroms of Silver (Cool-Amp is one maker (I have no connection, etc.).).

    You might also consider ensuring that the end of the Copper tube has a slight flare to it, or, at least, is deburred. Cutting Copper tubing tends to produce a burr, or slight squeezing of the tube at the cut point, and, if you're counting on a dependable release, you don't want anything binding at the end of the Copper tube.

    You could also consider some type of spring contact that would be inserted in the Copper tube. I'm thinking of something along the lines of a piece of Beryllium Copper that is folded and soldered to the wire.

    http://en.wikipedia.org/wiki/Beryllium_copper

    Good luck with it!

    Dave

    P.S. Remember that any landing you can walk away from it a success.

    1. Lester Haines (Written by Reg staff) Gold badge

      Re: Conductive Grease

      Well, we've got to have some of this, if only for the name: http://www.cool-amp.com/conducto_lube.html

      The open end of the tube has indeed been deburred, with a very fine drill bit which created the desired slight flare.

      I don't think we're going to get a spring contact inside, and it's an unnecessary refinement, to my mind.

      1. 4ecks

        Re: Conductive Grease

        Try these :- http://www.electrolube.com

        Available from CPC and much cheaper than cool-amp by the looks of it.

        1. Lester Haines (Written by Reg staff) Gold badge

          Re: Re: Conductive Grease

          Thanks.

  10. John Smith 19 Gold badge
    Unhappy

    Historically smoth breaking connectors have *always* been a problem

    I think it was the Blue Steel cruise missile that had a monster 100+ connector for it's INS and other functions that had to break on separation.

    I think they used something like a crumpled meter press stud on each connection.

  11. Zmodem

    whats a rocket assisted launch system that uses a balloon

  12. Ron 10

    Treating tubing

    This may be quite unnecessary, but:

    Improved connection contact behavior, if necessary. Clean the inside of the copper with a mild acid or cleaner of choice. Maybe a bit of abrasion.

    Coat wires to be inserted and the inside of the copper tubing with a material called Stabilant 22. This improves the contact between the materials and protects from oxidation/corrosion. Plain copper generates an oxide film fairly quickly. This insures max current flow for the circuit. The Stabilant actually conducts under pressure.

    This may change retention force to a bit lower.

    I use this stuff on any electrical connections. PC connections to power connectors. It is similar to magic.

    1. Zmodem

      Re: Treating tubing

      it would be easier to look at internal designs of hobby rockets then buy some brackets from model then look at a better eay

      1. Zmodem

        Re: Treating tubing

        some of the 8 foot custom rockets can go 1.5km high, you can buy kits and parts easy with a google search and download simulators http://www.thrustcurve.org/simulators.shtml

        and make orbital rockets http://www.instructables.com/id/Homemade-orbital-rocket/

  13. PKM

    Magnets

    At the risk of making a brilliantly simple thing a bit less so, would a small magnet on the outside of the copper tube help keep the inserted steel wire pressed against the inside of the tube until the point of release? Seems like it would provide a little friction to help stop the wire from being vibrated out of the tube during ascent but not really impede disconnection.

    1. Lester Haines (Written by Reg staff) Gold badge

      Re: Magnets

      Hmmm. Interesting...

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