air starting

Discussion in 'Low Power Rocketry (LPR)' started by havoc821, Feb 18, 2003.

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  1. Feb 18, 2003 #1

    havoc821

    havoc821

    havoc821

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    How exactly does airstarting work? Does it kind of work the same as staging except different? I have heard a lot about it, and it looks really cool to watch one launch, I just don't know how to do it. Any Suggestions? :confused:
     
  2. Feb 18, 2003 #2

    Mike

    Mike

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    Well firstly airstarting is really a high power kind of thing so isn't used in low power, I'm guessing that you want to do it with LPR motors since this is in the LPR forum!

    I think (but I'm not too sure so don't quote me on this) that electronics are used to time a ceratin interval from lift off and then the motor is inginted using an onboard power supply, this means lots of weight which can't be lifted by LPR motors. I beleive that people use it to get higher altitude, a larger motor is ignited first to get the rocket moving and then other (usually smaller) motors are ignited in the air so their thrust isn't used in getting the rocket moving, I'm sure there are other reasons too though.

    The standard method of staging (ie booster motor sends hot particles to upper motor) is kind of airstarting, the motor isn't ignited on the pad.

    I'm sure others will chime in, HTH.
     
  3. Feb 18, 2003 #3

    Micromeister

    Micromeister

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    very nice explanation mike:
    two points, I'm not at all sure why the term was coined as every single "Staged" rocket ever flown has used electronic ignition of the upper stage or strap-on boosters, I am speaking of real launch vehicles now. and second with the micro electronics and super high current capicators available today we do indeed use electronic staging, gap stageing, and of coarse contact staging, for Low power rockets as will as many LMR models.
    I first heard the word in 1993 before Naram-35, in connection with 3x1/2A cluster altitiude competition. The then National contest Board Chariman Matt Steel, make a very bad decision to allow "airstarting" which by the way is really called Stepped Staging, in cluster altutiude competition. This problem has been eliminated by a contest rules change. but the term seems to have continuted, and I think addopted by the HPR folks, or possible Matt brought it to model rocketry from his former HPR business no defunked North Coast Rocketry.

    havoc821: check out www.perfectflite.com for info in staging timer the size of a postage stamp and www.panasonic.com for info. on Hi amp 4.7 farad super capacitors that can be used to replace the batteries in the circuits. the whole deal will fit in a BT-4 easily, TT-4 (10.5mm) with a little work
     
  4. Feb 19, 2003 #4

    dluders

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    In Chapter 10 of Mark Canepa's excellent book, "Modern High-Power Rocketry (http://www.modernhpr.com), it talks about "Airstarting High-Power Rocket Motors: A Case Study." He explains that

    "An airstart is defined as the ignition of any motor after the first motion of a rocket. This may be achieved by way of outboard boosters starting after a central motor has lifted the rocket off the pad, or in the reverse. Either way, airstarting in modern high-power rocketry is typically accomplished by using onboard timers to fire an igniter, or series of igniters, after the rocket has left the launch pad."

    Blacksky Timer 2, Adept, Olsen, and Public Missiles Limited (among others) all make good timers for high-power.
     
  5. Feb 19, 2003 #5

    Micromeister

    Micromeister

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    Ah! so airstarting is nothing by plan old everyday Staging, that's what I thought.
     
  6. Feb 19, 2003 #6

    havoc821

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    I guess I didn't know airstarting was so complicated. I heard aboout it in the high power forum, but I was wondering if it could be low power. From what you all said, it appears that the only way to airstart is to use an electronic timer. If you would airstart, would you ignite the main motor first or the boosters first? Would it be possible to route the hot gasses/burning propellant from the main motor to the outside boosters to eliminate the need for timers, or would this be considered staging? :confused:
     
  7. Feb 19, 2003 #7

    dluders

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    One CAN airstart a black-powder (A-E impulse) rocket motor. Use Thermolite (underwater fuse) that runs from the nozzle of the booster rocket's motor, up into the 2nd-stage motor. When the first stage lights, it ignites the Thermolite (which burns at a rate of 1 inch per second, I recall). After a few seconds, the lit "fuse" ignites the second stage of your BLACK POWDER-based motor. The above procedure won't work for Ammonium Perchlorate Composite Propellant (APCP) motors, such as Aerotech reloads.

    Thermolite burns HOT, so be careful that it doesn't burn your fins or rocket body tubes!
     
  8. Feb 19, 2003 #8

    Micromeister

    Micromeister

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    havoc821:
    Step staging (I refuse to call it airstarting) can be done in any number of ways, depending on which motor(s) you wish to ignite first, and the location(s) of the additional motor(s). Other considerations; will you be dropping pods or stages or retaining all the used motor casing(s) dead weight.
    I've cluster ignited 3 and 4 BP motors then ignited an upperstage motor 3 ft away from the main cluster with nothing more complicated than a mercury switch, safety disconnect plug, standard estes igniter and a 9volt battery. In some very small Scale altitiude models we've staged a 10.5mm motor upper stage with that perfectflite stageing timer and two 4.7F super Caps. replacing the batteries I mentioned. Yes Step Staging can get a little complicated further unless you have a LEP you can't use thermolite fuse anyway it to is a controlled substance. Gap staging can be very effective, If you vent the hot gases near the upper stage motor. I've used this method up to 10" between motors with about 99% success. As the Electronic components get smaller and smaller I'm sure we well be able to ignite upper stage clusters very soon in Standard and even micro sized models. I am currently working on a 4 Micromaxx clustered to a mmx upper stage model useing a staging timer and Cap.discharge system. This model is a total of 12.75" long with the largest body dia of 13mm. With a little thought you can do just about anything you want. Ho! don't forget about the micro servos now available for Radio control as another source of upper stage R/C ignition. :D
     

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