Should I be thinking about Hybrid?

Kevin, This Contrail System is looking better and better.

-> I-307 573NS

-> I-333 556NS

-> I-400 432NS

-> I-290 Sparky 488NS I did notice all these motors use the 36 > >

Contrail Motors come with the necessary igniter, injector and line set when purchased. Each of those items, including the fuel grain are single use items. The Nozzle is a reusable graphite nozzle that is included with your purchase of hardware.

Contrail Motors do not require CSFM Approval. Hybrids are not classified by the CSFM and do not need the same approval as do AP Motors.

The Hardware Kevin refered to actually has 8 different Reloads certified in it. I-210-PVC I-333-PVC J-150-HP J-246-HP I-307-HP I-400-HP I-727-HP I-290-Sparky

Please note the I-727-HP uses a special > Kevin,

Thank you for verifying that the hybrids don't require CSFM approval. That's the info I'm getting from our member's list. 8^)

James

Laura,

Looks like Tom has it. The hybrids don't require CSFM approval. 8^)

James

Try the Sky Ripper Motors

They really rock and are simple to use with most ground suport systems.

Mark A Palmer

Laura,

Despite recommending the Contrail motors, I think *very* highly of the Skyripper motors as well. Although they offer fewer grain / injector / nozzle combinations, they are strong performers, very reliable, and easy to fly. I find they are also easier to clean than the Contrail motors, generally showing far less blow-by. The quality of machining and finish is outstanding.

Skyripper motors currently hold the hybrid H & I TRA altitude records. They are well worth a look. I certified L1 on the 38mm H155, and between the 29mm & 38mm motor sets I fly just as many SR motors as Contrail.

FWIW, the 29mm Skyrippers are probably my favorite hybrid motors. They are serious performers, and very economical to fly. I recently lost one, and bought two to replace it, if that tells you anything.

The 38mm SR motors have 2 certified motors per case size. You select the impulse by choosing the reload type: PVC is good, polypropolene (PP) is slightly better. The four SR 38mm cases give you eight motor combos, full G thru baby J.

As far as weighing N2O - historically Aerotech hybrid motors required you to weigh and pre-load the N2O, but all of the current crop of monotube motors require you to fill the N2O flight tank from a distance of no less than 100 feet, just before launch. At a nominal operating pressure of 750psi, there is only something like a 2:1 safety margin on the flight tank.... not something you want to stand close to.

Kevin O

Kevin, I didn't get the impression that anyone was putting Sky Rippers down. I have read a lot of good things about them. Thank you for helping clarify some confusion about the grains. Am I wrong or do the contrail motors seem to have greater lift. My rockets are a little heavy. My L1 rocket weighed in at 5.5 pounds with glass and all. When I start to add electronics, I can see the weight going up even more. I will try to keep the weight down, but so far it's not my forte. Anyway, I guess I'm saying that I like the thrust that seems to be greater with the I impulse Contrails motors. From what I could find out about the Contrails motors and I could be wrong, it seems that the hybrid average thrust approaches the AP of the same class. I thought I saw that Sky Rippers, like the Contrails motors have a set of hardware that will work for both L1 and L2 flights. Let me know your thoughts..

I will be look> >

Thank Alex, I appreciate all the information on the Hypertek motors. I didn't realize there were that many possible variations with the two tanks. Is it possible to ignite the Hypertek using pyrogen and do all the high voltage ignitors need O2?

Alex Mericas wrote:

Laura,

Thrust numbers of hybrid rockets are hard to compare to that of APCP motors, for a couple of reasons. Take a look at

About halfway down the page there is an outstanding explanation of how the operation of hybrids affects the certified thrust.

Add to that monotube hybrids have a highly regressive thrust curve, and the initial thrust is much higher than the average thrust. I frequently launch a

6+ pound (dry weight) rocket on the SR H155, and it flies beautifully. The rocket, all up on the pad with nitrous loaded is a bit over 7 lbs.

The Contrail motors do have good average thrust, but it comes at a price. A given amount of nitrous plus a given amount of fuel, burned at the same rate, yields a certain total impulse, no matter the manufacturer. The rub is in how fast it is burned. If you look at the impulse ratings for the "slow" Contrail motors you'll find they match the SR average and total impulse ratings pretty closely. What Contrail has done is to add different size nozzles and injectors, causing the engines to burn the same amount of oxidizer/fuel in a shorter time, giving higher AVERAGE thrust. However, as the motor speed goes up it appears that the efficency of the motor goes down, so that the faster motors have higher average impulse but lower TOTAL impulse. Not a huge amount, but enough to be noticeable.

Also, the conditions under which the motors are rated/certified makes a difference. The most important factor is temperature of the N2O. If I understood correctly, SR bases its' ratings on an ambient temp of 70F (~750psi), Contrail on 85F (~875 psi). This difference will affect the published performance of the motor. As the temp of N2O rises it becomes less dense, thus offering less O2 for total thrust, though it pushes the average thrust up a bit. Personally, I like to use pressures of 650-700 psi, since it gives killer performance and creates much less strain on the hardware. I've seen folks tank and launch at 900psi, but I'll pass at that pressure...

The Skyripper 38mm motor set does indeed span the range of motors from G to baby J, so is great for L1 & L2. Todd also has a series of 54mm motors in process for certification. One thing I noticed on the SR website is a larger nozzle/injector set for the 38mm motors, which will increase the average thrust of the motors to ~250NS on PP fuel. I'm looking into that for myself...

Also, RockSim or SpaceCad are your friend :) When in doubt, sim it out....

Kevin O

Thanks for replying Kevin. I could not have said it better myself. I recently flew the 29mm H at XPRS in my daughters Snitch. Easy set up easy clean up! In fact I found it mucheasier to build and clean then AT RMS. They are extremely reliable, simple and easy to use (1 set of internal components...Noxxle, Injector, bulk head etc). Nothing to mix up. I have seen a whole bunch of these motors fly..they sound, look and perform great!

Mark Palmer

Laura,

Dollar bills and credit cards burn to quickly. Some times they ignite spontaniously. Mine are always burning a hole in my pockets.

KT

Look out. If they burn faster than 7mm/sec, you're gonna need an LEUP for a credit card.

Who is the first lady of NAR ?

I've been in the NAR since the early 70s and never heard of that one.

She's the wife of the NAR President.

Or maybe Bob in a dress.

The president's wife. Just like any other president.

Thanks, Steve. I'll be all day getting THAT image out of my head.

Bill Sullivan

You're just jealous because the voices don't talk to YOU!