Fire 3 Strap-On (Parallel-Staged) Boosters, Then Air-Start a Central Motor?

I'm thinking about building a PARALLEL-STAGED rocket, whereby 3 ea. strap-on boosters lift a central rocket that air-starts when the boosters stop burning. The 3 ea., strap-on boosters would be ignited simultaneously on the launch pad, and would lift the central rocket body tube upwards. When the boosters finish their burn, a long-burn motor in the central body tube would air-start and continue the rocket upwards as a "second stage."

The boosters would fall away from the upward-climbing central rocket, using hardware from HAKO Ballistics (see the story and pictures on the web sites https://www.maxthrust.net/displayarticle197.html and https://albums.photo.epson.com/j/AlbumIndex?u=3009006&a=30253388&f=0 ).

The booster motors would get the heavy rocket moving off the launch pad quickly. The boosters would have their own individual recovery streamers for a soft landing. The central motor would be a LONG-burning H45, I95, or something similar. The long-burning motor (by itself) would not have enough "Oomph" to lift the rocket off the pad by itself -- it relies on the 3 ea. boosters to provide punch and airspeed.

I know that electronics would be needed for air-starting the central motor. I believe that such a rocket COULD fly. Unfortunately, I don't believe RockSim has a way of modeling PARALLEL-STAGED rockets, so I may just have to figure out stability using the old "cardboard cutout" method.

Any ideas or words of wisdom concerning this "dream project" of mine?

Um, er... I hate to suggest against your dream project. But... I strongly suggest that you do not try this. Sure, if it all works as plan, then it will be a beautiful launch. But, if only 1 or 2 of the boosters fire, then you are in a world of hurt. You will get asymetrical thrust that could send your rocket thrusting horizontal which would be bad if it is toward the flight line. I suggest you reconsider. You should start the central motor and airstart the boosters.

There is a real good video somewhere on TRF. I will find it and post it here...

Check out daveyfire's post towards the bottom of this link:

https://www.rocketryforum.com/showthread.php?s=&threadid=1620&perpage=20&pagenumber=1

There is a Bruiser video that is a perfect example why your idea is a dangerous one.

The general rule (er, guideline) is to have the main motor get the rocket going and then light the airstarts. What's even worse is when the cluster only partially ignites and flops the rocket onto the ground before the main motor ignites. There was a shot one one of the VHS videos that I have showing a rocket under M power chasing a photographer around. Bet he had to clean his shorts out

That being said, I am seeing a lot of big, 2 stage high power projects that have a clustered first stage. This is really no different than parallel staging. But what I also see is these are very experienced people launching from FAR away cells in the middle of nowhere. I guess what I'm saying is is than the environment, your experience with clustering, and the RSO's mood also play into thie equation.

As Phil said, it will be much safer, and have a higher probability of success, if you use a higher impulse main and airstart the outboards.

It do sound like an interesting project, tho

I appreciate the guidance folks have provided here. I read the related thread concerning air-starting, and understand the risks involved. I will get a lot more HPR experience under my belt before I attempt the parallel-staged rocket. I know that safety is paramount.

Nevertheless, when I watched the LDRS 21 DVD about the Gates Brothers' rockets, I saw that they successfully lit 7 motors simultaneously in the first stage. I don't have nearly the same experience as those guys, but if they can do it, so can others like me. I don't see their rockets suffering asymmetric thrust -- all motors light on cue.

I could scale down the rocket and use BLACK POWDER-based booster motors and airstart a long-burning central motor (like Apogee's F10 with it's 7-second burn). When possible, I could use RockSim to ensure that the motors have enough "oomph" to provide stable flight. Using a "clip whip" and some good-quality igniters for the 3 booster motors, I should be able to light all 3 simultaneously if I give them enough juice.

The black powder motors will certainly be easier to light. This is what I am planning to do on my Stormbringer. It has 8 outboard 24mm mounts and a 29mm central motor. Am thinking about 8 D12s and a G35 or G80 airstart. You can see the progress to date by accessing my site via the link in my signature - the next level link is easy to spot.

I know people have success at lighting multiple motors at once. The only person that I have "seen" trying this is Mark Brown. And believe me Mark is no dummy. (well, er, don't tell him I said that) Anyway, he has a LOC Viper with 3 motors. He has yet to have all 3 light with a whip clip. I would estimate about 10 launches. It's always 1 or 2 that don't light. He even uses a small amount of thermalight to help light the motors.

I'm in the process of building a 6x38mm 1x54mm adaptor for my elDiablo. (if I can get the rings back from being cut) That will be a central 54mm for launch, then 6 38mm airstarted. If that ever works maybe I will know more about clustering.

i think you should do it just line the motor with thermite a guy at my rocket club launch 4 K550 st the same time and all when well and it was great flight of cource everyone was nervers that new what could happen but it was such a cool flight

Yes... that video that PGerringer is making reference to definitely made an impression on me. I was there at LDRS XVII when some guy (I don't remember his name) tried to fly his rocket on an APS M Redeye core motor, and four DPS Yellowjacket outboards. Of course, being an M Redeye, the core motor took forever to come up to pressure. The 4x I370YJs tossed the rocket out of the tower, and the central M lit. Larry Zupnyk was the unfortunate man being chased by the rocket. As for the GB's launch of Athos II, those igniters were prepared by AMW for the hard-to-light Green Flame propellant. When Paul Robinson hit the button, you could hear and see the motors coming up to pressure staggered. If you watch the video closely, you can see the motors come up to pressure over the first half a second or so. The rocket really moves out when the central M5100BB lit.

Yes, I'd shy away from cluster boosters. That's why.

Originally posted by PGerringer
And believe me Mark is no dummy. (well, er, don't tell him I said that)

Click to expand...

Hmmm...that's not what you said in chat the other day.....

(running like hell)

Actually it was RStaff talking about the "M" chaser...

Matt, it is true that clusters are absolutely beautiful. But when they go wrong, they go really, really bad. Having one motor as the booster minimizes the bad.

Although, there could be a weight factor too. An "A 1/2" going bad probably isn't as devistating as an "M" chaser. There is some physics involved somewhere...

(throwing a motor casing at Kermie)