25% scale Aerobee

[JohnCoker]

After only 16 years, I finally completed my first-started scratch-built rocket!
jcrocket.com/aerobee.shtml

 

[mpitfield]

After only 16 years, I finally completed my first-started scratch-built rocket!
jcrocket.com/aerobee.shtml

Beautiful work John.

 

[thobin]

Very nice, makes me want to get back to work on mine.

TA

 

[fyrwrxz]

John- one word: WOW! Obviously a tour de force by a stratospheric modeler. The combination of skills utilized to produce this beauty is stunning and shows the bleeding edge of technology now available at our (okay-your) fingertips. Brilliantly documented and executed. I'm going back to my corner now and work on re-inventing the wheel and trying to make fire....

 

[gerbs4me]

That is a very impressive rocket...great work!

 

[Aksrockets]

Beautiful work! Excited to see it fly at Aeronaut.

Alex

 

[AfterBurners]

Unbelievable!

 

[dch]

All excellent, from the tip of the nose to the end of the documentation. Have you decided what motors you are going to use for the first flight?

 

[JohnCoker]

Thanks for all the kind words!

Have you decided what motors you are going to use for the first flight?

I need to do final sims, but I planned for an I200/H220 to a J90/I65. (Basically I need the highest-thrust 29mm motor and pretty much anything 54mm in the sustainer that has low smoke.)

 

[patelldp]

Thanks for all the kind words!


I need to do final sims, but I planned for an I200/H220 to a J90/I65. (Basically I need the highest-thrust 29mm motor and pretty much anything 54mm in the sustainer that has low smoke.)

John -

You should have bought the CTI cases I had for sale! Well, I still have the 38-6G for sale...

The 3G 29mm would have held the H410 VMax for your booster, the 38-6G plus the space would hold the J94 Mellow for the sustainer!

 

[dixontj93060]

REALLY NICE!

 

[JohnCoker]

Here's what I'm planning on, an H195 to a J90; looks like it'll be a good choice (going only 7000' and staying under Mach 1). It's all about what happens during the first 1s of the flight anyway!

 

[morlock]

Here's what I'm planning on, an H195 to a J90; looks like it'll be a good choice (going only 7000' and staying under Mach 1). It's all about what happens during the first 1s of the flight anyway!

View attachment 176638

From the graph, I gather this is a 2-stager. However, the first stage seems to bring only marginal gains, at least in terms of altitude. Is this typical? From an efficiency perspective, is it worth it or is it done totally for the fun of launching a 2 stage?

 

[aerostadt]

From the graph, I gather this is a 2-stager. However, the first stage seems to bring only marginal gains, at least in terms of altitude. Is this typical? From an efficiency perspective, is it worth it or is it done totally for the fun of launching a 2 stage?

It is probably typical. Usually, the modeler wants a high velocity at the end of burn-out of the second stage, because this will generally give the highest altitude for the last stage. From physics, if there is no air drag, clearly the high velocity for the last stage will give the highest altitude. With air drag the trajectory is more complicated and it can be shown that an optimum delay time for the firing the second stage will give the highest altitude. All that being said it looks to me like John is not trying to over-do his first stage, because the velocity at the end of burn is relatively small compared to the delta-v of the second stage. Of course, the first stage has more to lift, but not having looked at all the details of this design, I am thinking a bigger first stage motor might be possible. However, since this is a first flight and John's model is already at 7,000 feet, I would think that this is plenty enough.

However, there is still another point. The real Aerobee-Hi had a small first stage solid motor to guarantee that the liquids of the second stage would be at the bottom of the tanks ready to be fed into the combustion chamber. So, the solid first stage was really there to increase reliability, not altitude. If John wants more of a "scale" flight and see the first stage drop away at a low altitude, this is the way to go.

 

[morlock]

Thanks @aerostadt for a very detailed answer.

Also, when I posted the question, I had not gone through the original link describing the rocket at length. Had I done that before, I may have been too awed and shy to ask my clueless newbie question

Congratulations John on an incredible build!

 

[JohnCoker]

Yes, aerostadt has it right; I am going for prototypical staging. In fact, the two burns will overlap, which is why I chose that booster motor. (The interstage is stainless steel and ceramic to briefly survive the sustainer motor burn.)

Back in 1998, after building a bunch of kits, I wanted to build a completely scratch rocket and started looking through Peter Alway's Rockets of the World for inspiration. The "Standard Aerobee" rocket is a great looking one and is two-stage, but what really turned me on was the fact that both stages fired at liftoff with the stages remaining together during booster burn.

 

[BrAdam]

Great looking rocket John. Where is the first flight and when? Please post video. I plan on using the build thread as a resource for my someday project of the Aerobee 150A.

 

[JohnCoker]

The AERO-PAC Aeronaut launch in early August (probably the only launch I'll be able to attend this year).

 

[aerostadt]

I think I will add a few words before someone comes along and corrects me. I checked my Peter Always "Rockets of the World" today. It states that the tall launching tower and the solid booster of the Aerobee-Hi was to get the sounding rocket up to speed to be fin stabilized. It does not talk about positioning the liquids at the bottom of the tanks. It appears that the Wac Corporal and the Aerobee-Hi both had the same purpose for using the small rocket motor. Both the Aerobee-Hi and the Wac Corporal had hypergolic propellants, thus avoiding the design of an ignition system. Red Fuming Nitric Acid (RFNA) was very popular in those sounding rocket days. It was also used by the Germans in WWII. The Aerobee-Hi had pressurized propellant tanks that were opened by a valve that had an inertia sensor detecting lift off. The Wac Corporal solid booster burned for about 0.6 seconds and the Aerobee-Hi booster burned for about 2.6 seconds. On one occasion the Aerobee-Hi valve started leaking without warning and the second stage started firing. The launch controller then decided that it would be best to fire the solid rocket booster immediately and the sounding rocket took off instantly.

 

[grouch]

Unbelievable. I can't wait for the flight footage.

 

[JohnCoker]

I want to stress again what a great resource Rockets of the World is, not just for scale modelers but also for rocket history.
www.arapress.com/rockets-of-the-world/