Switching to Aerotech RMS Engines

[bkent1@mac.com]

I have a Estes D-Resion Tomahawk and am thinking of migrating over to the RMS engines from Aerotech. I'm just getting back into rocketry but I read several posts on the Estes Big Daddy (uses same engine as D-Region Tomahawk) and they referenced the Aerotech F24-4 as a good engine that drove alot higher altitude.

Should that engine also work as well on the D-Region Tomahawk?

Thanks,

Bill Kent

[Mark II]

I have a Estes D-Resion Tomahawk and am thinking of migrating over to the RMS engines from Aerotech. I'm just getting back into rocketry but I read several posts on the Estes Big Daddy (uses same engine as D-Region Tomahawk) and they referenced the Aerotech F24-4 as a good engine that drove alot higher altitude.

Should that engine also work as well on the D-Region Tomahawk?

Thanks,

Bill Kent
The delay of the F24-4 is too short; use the 7 sec. delay version instead. The mass of the F24 is about the same as that of an Estes E9, so you should not have any problems with stability. Lengthen the shock cord as necessary so that it is about 3x the length of the body tube. Depending on how much wind there is, it might be a good idea to reef the chute just a little bit, too, to cut down on the drift. You ought to get a real nice and high flight with that motor. Make sure that you take a couple of pictures of it beforehand, though; one to remember it by, and one to put on milk cartons. :D (Just kidding; you won't have any trouble getting it back. Probably. ;) :D)

Mark

[ghrocketman]

An Aerotech RMS24 F24-7W most likely would send the Estes D-region Tomahawk somewhere close to near-earth orbit.
DON'T do it with a RMS case unless you like throwing $40+ dollar RMS cases away.
If you must launch this on an F (any 40n-sec E will put it WAYYYYYY up there) use a single-use F as most likely you WILL lose the rocket.
Maybe you could find some 24mm SU Ellis Mountain F's or some old discontinued 24mm Aerotech Econojet F21's.
Otherwise the biggest single-use 24 mm readily available engines are the Aerotech E15 and E30, both of which are full-impulse 40 n-sec E's.

[Engineer Kelly]

When i built my tomahawk and also built it in rock sim. A f-24, in rock sim, will reach an alt. of about 1900 feet..

From jimz plans (D-Region Tomahawk)

[ghrocketman]

1900 feet with a rocket this small is quite high considering the wind drift that will occur on the supplied chute.
Anything short of flying at a wide open tree-less huge field or Sod Farm most likely will result in loss of the rocket.
I don't know too many people that like losing RMS cases needlessly.

The Big Daddy is a whole different story....MUCH more drag and heavier....not sure what RockSim says, but my Big Daddy flies a fair bit lower on a RMS24 F24 than my Semroc AeroDart goes on a lowly Estes E9, which Semroc says goes to 800'....my guess is my Big Daddy (beefed up with aircraft plywood TTW fins and plywood centering rings, using all epoxy construction) hits about 500-600' on the F24. It's now heavy enough that it cannot fly on an E9 and is lucky to hit 125' on a D12.

[Mark II]

An Aerotech RMS24 F24-7W most likely would send the Estes D-region Tomahawk somewhere close to near-earth orbit.
DON'T do it with a RMS case unless you like throwing $40+ dollar RMS cases away.
If you must launch this on an F (any 40n-sec E will put it WAYYYYYY up there) use a single-use F as most likely you WILL lose the rocket.
Maybe you could find some 24mm SU Ellis Mountain F's or some old discontinued 24mm Aerotech Econojet F21's.
Otherwise the biggest single-use 24 mm readily available engines are the Aerotech E15 and E30, both of which are full-impulse 40 n-sec E's.
I was thinking that it would be a high flight for sure, but would not go out of sight. I was estimating about 1300 ft. or better (based on a 1.8" frontal area and an empty weight of 9.2 oz., as listed in the EMRR review). Naturally he should fly in in a great big, flat field; with low or no winds, he should have no problem recovering it, so he would be safe in using his reload motor, I would think. On a sunny day with a clear, bright blue sky, he should be able to see the whole flight; the bright red and white 38" long Tomahawk would be close to being just a speck at 1300 ft., but would likely still be visible as long as he tracked it carefully and kept his eye on it (and had extra spotters to help). Once it got below about 900-1000 ft., I would think that it would be easy to follow for the rest of the recovery, as long as he was looking in the right part of the sky (true for any rocket). Caveat: this is just an estimate, though, as I have not yet built or flown this rocket.

If Engineer Kelly's estimate of 1900 ft. is right, though, all bets are off. To increase his chances of finding it, Bill ought to consider putting a loud beeper in the rocket in that case. If EK is right, then he should consider switching out the standard parachute and using an X-form chute, instead. I'm not so sure that using a streamer instead of a chute is such a good idea. It would cut down on the drift by substantially increasing the rate of descent, but a fast descent from that altitude would bring with it a much higher chance of damage to the rocket. This is a scale model, after all, so I would presume that Bill would like to preserve the looks, all other things being equal. Also, a rocket descending quickly on a streamer is harder to spot and to track from a very high altitude, especially if it is on a trajectory that takes it more than a little distance away from the pad. One thing that he could also consider doing is attaching a reflective Mylar streamer to the shock cord at the same place as the attachment point for the chute or just below it on the cord, not to act as a recovery device, but to increase the visibility as the rocket descends from the kind of altitude that EK is talking about.

I think that ghrocketman's advice is is the best approach, though. If he hasn't done so already, Bill should try flying his Tomahawk on some composite propellant E's first, to see how it performs on them, before he thinks about airing it out on an F.

Just my thoughts.

Mark

[bkent1@mac.com]

Guys,

Thanks so much for all the input. I'll go with the RMS "E" engines first and see how that plays out. Are reloads really cheaper than Estes single use engines in the long run?

Thanks for all the replies, greatly appreciated!

Bill Kent

[jj94]

Guys,

Thanks so much for all the input. I'll go with the RMS "E" engines first and see how that plays out. Are reloads really cheaper than Estes single use engines in the long run?

Thanks for all the replies, greatly appreciated!

Bill Kent

Well, in a simple response, no, reloads are not usually cheaper than Estes. A pack of 18mm D13/D24's average around from 9-13 dollars, and you can get Estes D's for about the same price (though they don't offer 18mm D motors :D). A pack of 24mm E/F loads are a bit more expensive and are usually >13/14 dollars unless you hit a good sale. Estes E motors can be bought for about the same price. But with the high cost of the case, reloads will generally be more expensive. The good side to reloads is power and visual/audible appeal. APCP can give much more power than normal BP can so then that means more powerful motors in a smaller amount of space. That's how 18mm D's can be made and yet they have the same size as normal BP 18mm motors. Same with 24mm reloads. I guaruntee you that you will never see a 24mm BP F motor with the same size as a normal BP D motor. However, 24mm E, E, and F motors with the same dimensions as BP D's are in existence because of AP propellant. Also, they are much louder with an aggressive roar, unlike BP motors. It's really amazing, how loud they can be. The exhaust is very impressive too. There are different propellants for AP motors that can give either a white exhaust flame with a bunch of smoke, almost no flame and no smoke (but it's an efficient propellant), and just thick black smoke (not very efficient, but they have long burns and are cool).

[ghrocketman]

Actually per n-sec of impulse, Aerotech RMS E's are indeed cheaper than Estes E9 engines.
One has to remember an Estes E9 is only 28 n-sec of total impulse. All currently made Aerotech RMS E's (24 and 29mm) are full 40 n-sec max-impulse E's. The only Aerotech E that was ever below 40 n-sec was the old 18mm RMS "baby" E that was 22-23 n-sec. That one has been gone for YEARS unfortunately.
An Aerotech E will fly any rocket much higher than any Estes E just due to the additional total impulse.
The Aerotech E is equal to an Estes E9 engine PLUS an Estes C6 engine PLUS an Estes A8 engine.
Going from an Estes D12 to an Aerotech E is a huge jump in that one Aerotech E is equal to more than TWO 17n-sec (do not believe the 20 n-sec figure Estes publishes for the D12) Estes D12's.