- Joined
- Aug 27, 2011
- Messages
- 11,628
- Reaction score
- 6,267
Named DoubleOrNuthin, since as designed if the upper stage failed to ignite or separate it was going to be an ugly flight. Fortunately worked.
This is a two stage bird. Based on BT-50, the lower stage is 39 inches long (36" plus enough length for motor mount AND overlap for fitting the sustainer engine into the forward end of the booster.) Specifically the distance between the upper end of the booster motor and the lower end of the sustainer motor is 36".
Booster is supplemented by two outboard 9" BT-20 engine pods. Purpose of the engine pods is really NOT to provide added thrust, but the outboards contain parachutes to carry this relatively large booster safely back to launch site. The problem with the really long booster is that it is difficult to get it to tumble back, as even after separation it tends to be stable and return ballistically. For any that have followed my builds, I am still working on a horizontal spin recovery booster, but figured I would work on that separate from my attempt at successful extended length gap staging.
Upper stage is about 19.5" long, minimum diameter BT-50 plus nose cone.
There are 4 holes in the upper end of the booster segment created with a hole punch just below where the upper stage engine "nests" into the froward end of the booster. These are designed to vent the gases to prevent premature separation before sustainer ignition.
There is a BT-20 "chimney" or "stuffer tube" extending from the front of the booster engine (basically acts as thrust ring) to just below the vent holes at the forward end of the booster body.
Launch lug on the booster section only--- the sustainer is not designed for independent flight.
While I usually don't finish my rockets, I figured this was going to be a fairly high flight for a minimum diameter LPR bird, so painted the upper stage fluorescent pink. Was glad I did.
Motor configuration:
Booster center motor D12-0. Two Outboards were Quest A6-4s. Again essentially all I needed from these outboard motors was a delay and an ejection charge to deploy the chutes on the booster after separation. I would probably have used Estes A8-3s, as a shorter delay would have been better, but wanted to use Quest Q2G2 igniters as according to what I have learned on this forum they are more reliable for clustering, and they fit better into the Quest A6-4s than the Estes A8-3s.
Sustainer was D12-7.
All engines were friction fitted for first flight. Second flight booster engines were taped to outside of rocket (for convenience), sustainer engine still friction fitted, as the rear 1 inch had to be free to insert/nest into the booster.
Recovery: Booster contains two 12 inch chutes in the outboards. When deployed, the attachment site while only 9 inches from the tail is still FORWARD of the CG of the 39 inch booster when the D12 and two A6-4 engine casings are included. Thus by design the booster should descend under chutes tail down. Fins are slightly forward swept. Hope is that the impact site will be on the protruding engines sticking out of the tail and not on the body or fins.
Weather was cold, about 30 degrees with full cloud cover. Winds were less than 4MPH, which was OUTSTANDING. I have big fins on the booster, to balance off the small but relatively markedly forwardly place sustainer fins on the combined Booster/Sustainer launch configuration. I am not sure how much weathercocking I would have gotten if there was any significant wind. Also, I am horrible at guessing altitude but figured probably the sustainer reached 2000'.
First flight: Arrow straight boost, minimal roll. Estimate (roughly!) staging at about 200-300 feet. Straight flight of sustainer.
Both booster pod chutes ejecting, only one inflated (I am finding this common with two chutes, sometimes I think one opens first and slows things down enough the second doesn't inflate.) Booster came down horizontal fairly slow, with absolutely not damage.
Sustainer was just a visual range when ejection occurred, I have no idea whether it was at apogee or not. 7 second delay seems like a loooooong time to this LPR guy, especially when the rocket is already at 200 plus feet when it stages. Initially had sight of both booster coming down on single chute and sustainer under 3 streamers. Glanced to confirm trajectory on booster and when looked back, had lost sight of sustainer. Fortunately regained it. Booster recovery about 100 feet from pad, Sustainer about 150 yards away. Thank God for Pink Paint! No damage to Sustainer--- did discover that on flight one the Sustainer had spit the (friction fit) engine, which is probably why it took so long to come down!
Second flight was fairly similar to first. Straight boost, staging about 200-300 feet estimate, straight flight of sustainer. Both Booster chutes deployed but NEITHER opened, the streamer effect was enough to shift the Booster horizontal and it still came down lightly with no damage. Sustainer successfully recovered under streamers about 100 yards away, WITHOUT spitting the engine. No damage to Booster nor Sustainer.
Last edited:
