Simulating Bertrand R. Brinley's Alpha and Beta Rockets

ihbarddx · Feb 8, 2019

This topic came up on FB. It concerns two rockets described in Brinley's _Rocket Manual for Amateurs_. It's a book that got me involved in rockets back in 1960. It likely means a lot to others.

Didn't know exactly where to post. It could be propulsion. It could be here. You could argue it should be the X rocket forum, but even though the rockets use amateur propellants, the post has nothing to do with construction or propellant formulas. In the end, it's a collection of simulations, and most simulations are here.

Please see attached. There's a summary at the end.

Blackleaf99 · Feb 10, 2019

The Reaction Research Society in California probably has more experience with the Ft. Sill Beta than any other group. They have built and flown numbers of them into the hundreds, albeit spread out over decades.

You are correct to be suspicious of the numbers Brinley quoted for performance. Brinley himself was not from a rocketry background but collected information, organized a book then published this data to provide a much needed reference at that time.

The RRS typically used a mechanically agitated means to settle raw Zn/S powder into the rocket. It was not pressed or cast in any way. This resulted in an extremely fast burn time for the propellant load. Hence this also means an extremely short thrust profile. They would estimate the actual max altitude for a Beta vehicle in the 6-7K feet range based on total time of flight. A very far cry from the 20K altitude Brinley quoted in his book.

ihbarddx · Feb 11, 2019

Blackleaf99 said:
The Reaction Research Society in California probably has more experience with the Ft. Sill Beta than any other group. They have built and flown numbers of them into the hundreds, albeit spread out over decades.

You are correct to be suspicious of the numbers Brinley quoted for performance. Brinley himself was not from a rocketry background but collected information, organized a book then published this data to provide a much needed reference at that time.

The RRS typically used a mechanically agitated means to settle raw Zn/S powder into the rocket. It was not pressed or cast in any way. This resulted in an extremely fast burn time for the propellant load. Hence this also means an extremely short thrust profile. They would estimate the actual max altitude for a Beta vehicle in the 6-7K feet range based on total time of flight. A very far cry from the 20K altitude Brinley quoted in his book.

Thanks for the response.

I remember RRS. Used to correspond with George Dosa there.
Anyway, the purpose of the calculations wasn't to compute real world performance, exactly. After all, I used Brinley's value of Ve, whcih corresponded to an Isp of ~46.

ihbarddx · Feb 11, 2019

Sorry. Had meant to omit the response. How... awkward.

sghioto · Feb 12, 2019

What were the dimensions of the motor chamber in the Alpha and Beta rockets?
SG

ihbarddx · Feb 13, 2019

Both chambers have length 45 inches

The Alpha has an inside diameter of 1 5/8 inches
The Alpha has a throat diameter of .806 inches

The Beta has an inside diameter of 1 7/8 inches
The Beta has a throat diameter of .932 inches

sghioto · Feb 13, 2019

Using the dimensions from the beta rocket here is a thrust profile using a sorbitol based sugar propellant.
Propellant weight 5.32 lbs
Grain profile.... straight core... 1.755" diameter, .875" core, 45" length
Nozzle throat .75 inch
Impulse.......... 4316 N
This confirms the "L" rating of the sugar beta.
Currently my flight program is corrupt. Inbarddx can you run this thrust profile through your flight program? Curious if the altitudes match up with your results.
SG

ihbarddx · Feb 13, 2019

sghioto said:
What were the dimensions of the motor chamber in the Alpha and Beta rockets?
SG

It will likely have to wait for the weekend, but yeah. Sure.

sghioto · Feb 13, 2019

OK, Thanks
SG

ihbarddx · Feb 13, 2019

sghioto said:
OK, Thanks
SG

Hmmm... Just looking at it, you have an Isp of ~182, here. That's a bit high for KNSB, isn't it?

5.32*453.592 = 2413.10944 grams = 2.41310944 kg of propellant
4316 ns / 2.41310944 kg = 1788.564 m/sec Ve

1788.564/9.80665 = 182.5065 sec Isp

sghioto · Feb 13, 2019

ihbarddx said:
1788.564/9.80665 = 182.5065 sec Isp

That is too high. Expected ISP max at 140. I'll have to recheck the values used for the "a" and "n" used in the program.
SG

sghioto · Feb 13, 2019

Well the numbers are correct but the tail off shown on the profile does not look realistic. I modified the thrust curve to give a more realistic view in my opinion.
3040Ns
ISP 133
SG

ihbarddx · Feb 14, 2019

sghioto said:
Well the numbers are correct but the tail off shown on the profile does not look realistic. I modified the thrust curve to give a more realistic view in my opinion.
3040Ns
ISP 133
SG
View attachment 374552

Shoulda looked in before I did the thrust curve.
FWIW, the impulse on the last one corresponded nicely.

sghioto · Feb 14, 2019

ihbarddx said:
FWIW, the impulse on the last one corresponded nicely.

It's close, you have 144 and I estimated 133. My objective was to see if a beta sugar motor was actually feasible which it is.
SG

sghioto · Feb 14, 2019

BTW I just came across this page from RRS that was a launch last October using modified alpha rockets. Very interesting and they did a static test with data.
SG
https://www.rrs.org/tag/zincsulfur/

ihbarddx · Feb 14, 2019

sghioto said:
BTW I just came across this page from RRS that was a launch last October using modified alpha rockets. Very interesting and they did a static test with data.
SG
https://www.rrs.org/tag/zincsulfur/

Good article.

ihbarddx · Feb 16, 2019

Here are the sim results with the DATCOM drag profile.

sghioto · Feb 20, 2019

Inbarddx said: "Isp = 128.4624, which still seems high to me"
I would say that is right on target from specs I've seen from actual motors.
Thanks for the data.
SG

Simulating Bertrand R. Brinley's Alpha and Beta Rockets

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