Estes - Fireflash 2-Stage
Contributed by Niall Oswald (Contributed - by Niall Oswald - 10/30/03)
Modifications: As I was sorting the lower section, which was crimped above the motor mount, it occurred to me that the section I had cut off (motor mount and fin can) looked like a booster section. I simply added vent holes and a coupler and I had an 18mm booster. This meant making a new sustainer motor mount and fins, which didn't take long — it's simply a copy of the section I cut off, again painted black and white. The rear CR is set far enough up the BT to allow coupling to the booster (it's a gap-stager), all pretty standard stuff.
I re-rigged recovery with a 12-inch clear plastic chute (home-made) and a 12-inch metallic mylar streamer for visibility. This turned out to be a very good idea! I had previously attached Kevlar® cord at each end of the shock cord (it looks virtually impossible to replace a broken Estes cord on this rocket) so I attached the chute to the top piece of Kevlar®, so that if the SC broke the (heavy) nose section would hopefully be recovered OK. It's very flimsy and full of noseweight — not a good combination.
I think that's the lot, the overall impression is of a ‘meaner' Fireflash, which looks more like a sounding rocket than the original, IMHO. Construction:
Of course most of these were for repair - doing this from scratch would be easier. If you've built any rockets before, this type of mod should be no problem. Aside from the usual fin alignment and finishing issues, there's not much to mess up here. Just make sure the stages fit together OK and remember to make vent holes in the gap! A failed staging is not pretty! Flight:
Thankfully the tubes weren't crimped, so it was off to prep another flight. Flight 2) The booster coupler had been damaged by its hard recovery, and was a very tight fit with the sustainer. I was a little concerned, but decided that it should blow off OK with the ignition of the top stage, all being well.
The rocket drifted a fair way, and when I got to it, the booster stage was about 10 feet from the main stage. It didn't look pretty! On closer inspection, it was clear what had gone wrong. The booster was burned right through (the vent holes were a little toasted after the first flight), with the paint blistered and impressive scorch marks below the vent holes. The remains of the coupler were still stuck into the top stage, and there was a lot of residue around the spent motor.
Summary: Cons: Torched the booster. However this should be easy to fix, requiring a new length of tubing only. Other: Flight Log
What You Can Do
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Brief:
As I was doing this, I realized I could
easily make a minimum diameter ‘D' booster, a la Commanche-3, and this
would really get the thing moving :-). I wasn't sure launching this rocket in
any wind on a C6-C6 combo was such a good idea (visions of horizontal flight).
So again the original fins were copied in balsa and the (very simple) booster
was made as before. All balsa fins were filleted with PVA (super PVA) glue, for
a strong bond (I hoped) and the booster was sprayed as per the new MMT section
of the sustainer.
I think that's about the limit of the
mods — I now had a bigger, better Fireflash, with the facility to fly 18mm
to 18mm or 24mm to 18mm, meaning up to a medium E impulse. According to
SpaceCAD, a D12-C6 flight would result in a flight to around 2350-feet —
not bad I thought, considering the fairly mediocre performance of this rocket
on C6s. Due to the heavy nose, the sustainer (according to the sim) should
coast well, having been accelerated to around 150 ms by the booster.
Flight 1) I loaded it “to the
max” with a D12-0 and a C6-5 (it was rather windy so I thought a C6-7
wasn't a good idea). I don't suppose either flight hit 2350-feet due to the
wind, but they certainly went a long way up for a model. I launched off a
standard porta-pad, no problems here.. The first launch left the pad quickly
and boosted into the wind, moving quite fast. The second stage lit fine and
continued on up. I love the smoke trails you get from multi-stage models, and
the Fireflash served up a treat.. However, the booster came in very fast —
I was watching the top stage, but saw it briefly, coming in ballistic. It
failed to tumble and went into the ground quite hard. The top stage made a nice
line of tracking smoke before ejection, and something definitely deployed. The
rocket came down fast, however, as the 'chute failed to deploy, getting jammed
inside the plastic transition between the BT-50 and BT-5. Despite the weight of
the rocket, it suffered only a broken fin (the streamer saved it) which was
quickly repaired with CA.
The flight was much like the first
flight from the ground — the D12 booster got the rocket going pretty fast,
and the top stage definitely lit. I could see that the upper stage smoke trail
wasnt even, but seemed to have bits coming out of it (if that makes sense - it
was ‘ragged' rather than smooth) and no booster was seen coming in. The
rocket coasted to apogee, and deployed both chute and streamer. The RSO said he
suspected the booster hadn't separated, and inspection via binoculars as the
rocket was descending revealed two sets of fins — not good news.
Obviously the booster needs rebuilding,
and I think more fins are in order, to hopefully promote a bit of tumbling.
Smaller vent holes are also going to be made — 5mm is a little much, and
seems to allow too much gas to escape.