FSI F7-4 - Info?

I have friend and fellow rocketeer that recently came across five or so Flight Systems Inc. F7-4 rocket engines Mfg. June 1982 and I am wondering, what is the consensus on these motors? Should the motors be used? Are they safe (I think they probably are, but just to be safe...)? Do they have any historical or any other significance other than that FSI is (Or was.) out of business meaning they are OOP?

Here are some pictures... (Never saw it, never happened, eh?)






Sorry, a little blurry, they were taken with my phone.
Fyi, I have posted this on The Rocketry Center as well.

They were unreliable when new. F100s were worse.
33 years of storage would not make them better.

M

Glue fins on them and fly. When they work, they will only lift themselves. I was never able to get a straight flight with any rocket over 1 oz.

They are no longer certified so they can only be flown at a TRA research launch or at a NAR launch after submission and approval under the old motor testing program.

Bob

I flew some in the 90s we got cheap. Pretty much need an Estes rocket as they barely lift their own weight. If unstable, they land shark around for quite a bit. I remember our Estes Phoenix doing this. Fun motors.

Don't what the diameter on these is, but I would think that it would make a great upper stage motor for a VERY light airframe, with like an E12 (24mm) or E16 (29mm) BP motor to get them going.

Thanks everyone. So basically they are only sentimentally valuable. And they can't be flown, technically, so... Any ideas on how to use them? Btw, neither of us are members of Tripoli or NAR.

BuiltFromTrash said:

Thanks everyone. So basically they are only sentimentally valuable. And they can't be flown, technically, so... Any ideas on how to use them? Btw, neither of us are members of Tripoli or NAR.

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As others have referenced, make a flying motor or a lighweight throw-away vehicle and go fly it on your own. Just incorporate some kind of recovery device so it comes down softly. Being an endburning BP motor I bet you could use it as an upper stage with a 24 or 29mm booster like a D12, E12 or E16. And take pics/video and report back here!!

Back in the early 1980s the F7's were used for RCBG and small light rockets you didn't want to see again. They were somewhat prone to cato b/c of nozzle plugging and the now well known sensitivity of large grain BP motors to thermal cycling (which wasn't well known then). I've used plenty of 30+ year old BP motors but I wouldn't put an old F7 in anything I cared about

They carried the nickname of "9SOT" - Nine Seconds of Terror!

8SOT.

https://www.nar.org/SandT/pdf/FSI/F7.pdf

Estes F15 is so much better.

caveduck said:

Back in the early 1980s the F7's were used for RCBG and small light rockets you didn't want to see again. They were somewhat prone to cato b/c of nozzle plugging and the now well known sensitivity of large grain BP motors to thermal cycling (which wasn't well known then). I've used plenty of 30+ year old BP motors but I wouldn't put an old F7 in anything I cared about

They carried the nickname of "9SOT" - Nine Seconds of Terror!

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Nobody I know flying them in that era ever said "8SOT".

I flew a lot of them and I heard 7SOT since the early versions actually only had 7 second burns. They tweaked them a bit when S&T was going to call them an E motor and they added a bit more propellant that put the burn time from 7 to 8 seconds and got them safely over the F total-impulse line.

FYI, I tested several on the MIT Test Stand in the 1970's.

caveduck said:

Nobody I know flying them in that era ever said "8SOT".

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Pretty cool.

Hopefully I will reply back on the fate of these engines.

Rocket car.

I flew one in an Estes Optima back in 93 or so. It didn't go straight up exactly, but it didn't land shark either. Have VHS of that flight somewhere. Cool motors! I'd do what Rocketjunkie suggested and glue fins on them if I were you.

BuiltFromTrash said:

Pretty cool.

Hopefully I will reply back on the fate of these engines.

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Yes, I'd like to hear what happened.

As a youngster, I remember building my FSI OSO, and ordering some of their F engines...never got to fly them, we moved and then I went to college, etc.

I'm guessing (as others have said) the F7-4's would have been used in gliders, anything else light enough to lift off with that would need a longer delay.

See the old OSO instructions pic at https://rocketry.files.wordpress.com/2007/06/osoad.jpg

BTW, does anybody else miss those old hand drawn FSI build instructions? I sure do!

The_Lone_Beagle said:

Yes, I'd like to hear what happened.

As a youngster, I remember building my FSI OSO, and ordering some of their F engines...never got to fly them, we moved and then I went to college, etc.

I'm guessing (as others have said) the F7-4's would have been used in gliders, anything else light enough to lift off with that would need a longer delay.

See the old OSO instructions pic at https://rocketry.files.wordpress.com/2007/06/osoad.jpg

BTW, does anybody else miss those old hand drawn FSI build instructions? I sure do!

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I flew the F100 and F7 engines over 40 years ago and they were flawless, Actually found my old stash of F-100 engines

Like with any large black powder motor, it all depends how they were stored. Sometimes they work, sometimes they don't. When I was still flying F7s, I always used them as upper stages to D12-0 boosters. At some point in the 90's, all the ones I had blew up. But rraeford had great luck with them. I think he got a lot of the last fresh batches before Harold died and the company did too. Mine were all from 1978-80 and 1988.