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Old 11-19-2010, 06:42 AM
blackshire's Avatar
blackshire blackshire is offline
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Default "Delay-less" rocket design

Hello All,

Here are illustrations (see: http://www.samstoybox.com/toys/Aeronautic.html ) of a different Quercetti-type hand-launched rocket, shown on the box covers and experiment manual covers of an Aeronautical Lab Kit that was made by Science Fair and Logix Enterprises in the early 1970s. (I once had the Logix-made one, and I bought a copy of the manual on eBay last year.) The hand-launched rocket in this kit could be modified to operate as a model rocket that would not need to use the motor's delay and ejection charge. It could be done as follows (but first, a brief description of the rocket):

The Science Fair/Logix Enterprises hand-launched rocket had its body tube split lengthwise, partway up the body tube from the rear. The shorter portion of the split tube formed a parachute compartment hatch that was hinged (with self-adhesive decal material strips) at its front edge, and two of the rocket's four fins were glued to the hatch. A length of rubber band served as the hatch opening spring--one end was affixed to the rocket body tube just above the hinge point with a piece of self-adhesive decal material, and the other end was attached in the same way near the upper rear corner of the fin that was in line with the hatch hinge.

After the rocket was launched with a rubber band catapult, the slipstream kept the hatch closed until the rocket slowed almost to a stop very close to apogee, which was listed as up to 150 meters (490 feet). Due to the rubber band hatch spring's attachment locations & angle of attachment (it resembled a tail fin-to-fuselage roof wire antenna on a DC-4 or Cessna airplane), it required little tension to open the parachute compartment hatch at apogee.

For a model rocket version of this hand-launched rocket, the launch lug could be glued on in two or three interlocking pieces (like the interlocking hinge pin tubes on both halves of a door hinge). One length of launch lug would be glued to the edge of the hatch, and the other one (or two) would be glued to the body tube, adjacent to the hatch seam. When the hatch was closed, the two or three pieces of launch lug would line up, and the launch rod would pass through all of them to hold the hatch closed.

After the motor ignited and boosted the rocket off the launch pad, the slipstream would keep the parachute compartment hatch closed. The motor's delay and ejection charge would be unnecessary, as the hatch spring would automatically open the parachute compartment hatch when the rocket slowed nearly to a stop near apogee. A motor mount tube with a nose block glued into the front (say, a length of BT-20 glued into the rear end of the non-hatch half of a BT-40 body tube) would permit this rocket to use either zero-delay booster motors or ordinary delay-equipped single-stage and upper-stage motors, which would be expelled from the front-blocked motor mount tube at ejection (or at propellant burn-through, in the case of booster motors). Adding vent holes to the front of the motor mount (through the body tube) would allow the model to retain the motor by either friction-fit or with a motor clip.
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  #2  
Old 11-19-2010, 04:06 PM
Jerry Irvine's Avatar
Jerry Irvine Jerry Irvine is offline
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Default

Quote:
Originally Posted by blackshire
The motor's delay and ejection charge would be unnecessary

In the SU world, delayless is a feature not a bug. In the reloadable market any aftermarket mod is added labor and parts to plug it. If by design, a reloadable plugged motor might be less overall cost.

Jerry
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