There is no way that this rocket is successful, but darn it I am going to try! (Mach 5+ Composite Case 38mm rocket)

[lr64]

If you want to maintain Mach 1, that's a whole other story.

Speaking of minimalist approaches, Openrocket seems to show that a Scout with a composite 18mm motor could be faster and cheaper than a rocket using the Estes F15. Assuming you only wanted to fly it once, or your flying site was a large, featureless flat plain with nothing to hide the little rocket. Lake Champlain when frozen over, maybe.

 

[Adrian A]

Yep, gordon gave me back all 4 fins as well, they were right next to it. The object hanging down is the av bay. I glued it in place to make sure it didnt move and had to break it to take it apart.

This is an eye-opening and inspiring thread. One tip: If you orient your 400G accels at 45 degrees you can get 565 G range axially using 2 axes. Or a bit more if you can figure out how to align your accel to get all 3 axes sharing equally.

I’ve always used commercial motors because I’m a messy builder and don’t trust myself to safely mix propellant. But now I’m wondering how light of a rocket I could build if I laid up an appropriate amount of carbon around a Loki K627 liner in place of the heavy aluminum case. I also wonder now which large commercial 38mm motor has the highest Isp.

Maybe a 54-38 two-stage could get to 100km.

 

[Spacedog49Krell]

This is an eye-opening and inspiring thread. One tip: If you orient your 400G accels at 45 degrees you can get 565 G range axially using 2 axes. Or a bit more if you can figure out how to align your accel to get all 3 axes sharing equally.

I’ve always used commercial motors because I’m a messy builder and don’t trust myself to safely mix propellant. But now I’m wondering how light of a rocket I could build if I laid up an appropriate amount of carbon around a Loki K627 liner in place of the heavy aluminum case. I also wonder now which large commercial 38mm motor has the highest Isp.

Maybe a 54-38 two-stage could get to 100km.

Kip Daugirdas's MESOS is about the smallest size 2-stage short burn high velocity rocket approach to reaching space. Another approach would be a boosted long burn lower velocity sustainer like a boosted-ARCAS. Kip's launch from Black Rock could have reached 100km if it hadn't started tumbling.

 

[Spacedog49Krell]

If you want to maintain Mach 1, that's a whole other story.

Speaking of minimalist approaches, Openrocket seems to show that a Scout with a composite 18mm motor could be faster and cheaper than a rocket using the Estes F15. Assuming you only wanted to fly it once, or your flying site was a large, featureless flat plain with nothing to hide the little rocket. Lake Champlain when frozen over, maybe.

Yes, an 18mm composite F or G motor can power a small rocket past Mach 1. It has been done before. The caveat is thin paper tubes and wooden fins do not hold up to the stresses of supersonic flight. Make the airframe and fins out of composites.

 

[Brainstormz123]

This is an eye-opening and inspiring thread. One tip: If you orient your 400G accels at 45 degrees you can get 565 G range axially using 2 axes. Or a bit more if you can figure out how to align your accel to get all 3 axes sharing equally.

I’ve always used commercial motors because I’m a messy builder and don’t trust myself to safely mix propellant. But now I’m wondering how light of a rocket I could build if I laid up an appropriate amount of carbon around a Loki K627 liner in place of the heavy aluminum case. I also wonder now which large commercial 38mm motor has the highest Isp.

Maybe a 54-38 two-stage could get to 100km.

Rather clever, ill do that for the balls flight (might swap to a slightly slower but higher isp propellant as well which could bring it from 700ish Gs down to 350-400)

 

[kjhambrick]

One thing about orienting your axial accelerometer off-axis is that your 1-G offset must be read on the pad.

If you've got something hard-coded in your processor for the 1-G offset it could make a mess of your vertical inertial velocity and altitude

-- kjh

 

[Adrian A]

I’ve always used commercial motors because I’m a messy builder and don’t trust myself to safely mix propellant. But now I’m wondering how light of a rocket I could build if I laid up an appropriate amount of carbon around a Loki K627 liner in place of the heavy aluminum case. I also wonder now which large commercial 38mm motor has the highest Isp.

Maybe a 54-38 two-stage could get to 100km.

If I take my current sustainer design and replace the Loki 38-1200 aluminum case with an integrated composite body tube that takes 7 oz out of the rocket (the aluminum motor case is 14 oz), then a 2-stage M1350 to K627 rocket sims to about 360 kft in RASAero. Burnout at 40 kft over Mach 5.

I mean... I have these motors in my garage right now, though of course not the composite replacement case.

This seems like a good next-year project. First I need a completely successful 38mm minimum diameter multi-stage flight.

 

[StreuB1]

An .048" wall 2024 case would be a better bet than composite.

Our hardware is thick and heavy because we're all big dumb apes and also there is a cost to machining. If you are flexible, then reduce the OD of a suitable piece of AL tubing (38mm is the best to do this!) and then machine the OD down till you have enough margin to maintain a means of end closure.....radial pins or #4-40 screws.

 

[lr64]

An .048" wall 2024 case would be a better bet than composite.

That doesn't seem like much of a safety factor unless the case is well insulated enough not to lose its temper. 500 psi would get it to roughtly 7,600 psi, if I'm not mistaken. I notice that Aircraft Spruce has some fairly thin walled tubing around that size. But that doesn't leave thick walls for pins or screws.

 

[Adrian A]

That doesn't seem like much of a safety factor unless the case is well insulated enough not to lose its temper. 500 psi would get it to roughtly 7,600 psi, if I'm not mistaken. I notice that Aircraft Spruce has some fairly thin walled tubing around that size. But that doesn't leave thick walls for pins or screws.

I don't have Al machining capability, but I do have plenty composites experience, and I think the OP's methods in this thread are sound. This has been an inspiration that I think will accelerate my attempt at the karman line by years and thousands of dollars. But I don't want to hijack the thread further. I'll make a new thread for a 54mm-38mm space shot based on a composite case K627.

 

[lr64]

snip
I’ve always used commercial motors because I’m a messy builder and don’t trust myself to safely mix propellant. But now I’m wondering how light of a rocket I could build if I laid up an appropriate amount of carbon around a Loki K627 liner in place of the heavy aluminum case. I also wonder now which large commercial 38mm motor has the highest Isp.

Maybe a 54-38 two-stage could get to 100km.

If you're concerned about cooking mixed fuel, you might check out (deleted) at(deleted's) site. As I recall, you don't have to heat up mixed fuel and oxidizer for either one, though (deleted) requires pressing. I doubt Tripoli allows (deleted) but hypothetically the ISP is over 200 at 1,000 psi. Over 140 at that pressure for (deleted).

Making your own grains might allow you to tailor the burn rate for each part of the flight. Maybe you could keep it subsonic until the air is much thinner. Will the rocket keep flying straight at those really high altitudes?

If you're right about the 54-38, that makes it sound like the Karman is accessible to individuals with relatively modest resources.

 

[Neutronium95]

If you're concerned about cooking mixed fuel, you might check out RNX and A24 at Richard Nakka's site. As I recall, you don't have to heat up mixed fuel and oxidizer for either one, though A24 requires pressing. I doubt Tripoli allows A24, but hypothetically the ISP is over 200 at 1,000 psi. Over 140 at that pressure for RNX.

If you're going to get into composite propellant, just go with APCP. It's what the majority of people who mix their own motors have settled on for a very good reason.

 

[lr64]

A24 is pretty close to APCP plus aluminum. OOPS, I take that back, since it uses ammonium nitrate. I admit that it's not clear to me if A24 is stabilized or not. Personally, when I read the word "perchlorate", I think of contaminated ground water near military bases.

 

[Theory]

A24 is pretty close to APCP plus aluminum.

This statement is concerning for so many reasons.

Suggest we move this part of the conversation to the appropriate forum

 

[kjhambrick]

@lr64 --

Without going into specific details ... if you want to do some thought experiments / sims with APCP propellant grains in the free openmotor app...

All the info for openmotor and all the parts you need to build your own dream motor are available from Rocket Motor Components

RCS sells a number of flavors of 10.5 inch long x 38mm propellant grains.

And all the specs and bills of materials for existing Aerotech motors are published at RCS so you can start out by reverse-engineering known working motors in openmotor.

As for ISP ... RCS sells some pretty spicy grains ...

Assuming 1000 psi chamber pressure at sea level, the ISP of the available RCS propellant grains ranges from 166.2 sec ( Black Jack ) to 265.8 sec ( Propellant X )

HTH and have fun !

-- kjh

p.s. I am in Adrian's boat as far as mixing propellant at home.

In my case, I am afraid I wouldn't be able to keep my 4 year-old granddaughter out of the mixing bowl -- she loves cooking with Nana and building rockets with Poppy and I can just see her sneaking out to the garage to lick Poppy's rocket motor batter bowl

Maybe when she's older ?