Hypothetical design and altitude competition - Brain teaser

[CrocketRocket]

Hypothetical scenario:

You've entered a rocket altitude competition. You versus 10 other rocket competitors.

RULES:

The other 10 competitors have an unlimited budget.
You are the only competitor limited to a $100 budget = rocket kit, extra parts, engine. (altimeter not included).
The other 10 competitors can use ANY rocket kit from low power, mid power, high power.
You are the only competitor limited to using an low power Estes kit, although you can modify, add, remove parts, shorten, lengthen body tube, change fins.
Any motor size A-G
Clusters and staging allowed.
All rockets must have a payload bay containing an altimeter.
None of other competitors have much previous rocketry experience.
Rocket must have a recovery device.
Rocket must be found and recovered, but a crash landing will not disqualify.
The launch field is huge, (but a very tiny rocket could still get lost).
Only one launch.
Highest altitude wins.

PRIZE:

$500 and bragging rights

INTEL:

Based on the snooping you've done . . . 3 competitors have built their rockets shabbily, and will probably suffer catos. Other competitors purchased large impressive looking rockets but have unknowingly mismatched them with weak engines.

THE COMPETITORS:
1. cato
2. cato
3. cato
4. 600ft
5. 845ft
6. 865ft
7. 1010ft
8. 1850ft Aerodactyl 2 stage
9. 2250ft
10. 2450ft

What would you do to win this competition? What Estes kit would you use as your base start point? And what altitude would you aim to achieve?

My plans are a modified and lengthened Alpha (Apogee E6 engine) - projected at 3,500 feet

or

lengthened and tail-cone added Big Bertha (Apogee F10 engine) - projected at 3,200 feet
(these Open Rocket plans are rough estimates)

 

[C.O.B.H.C.]

Can it be scratch built and use electronics for deployment? If so a 24mm minimum diameter on a CTI G65W. Projected altitude 9K.

 

[Tractionengines]

Between you two options. I would go with the Modified Big Bertha.
* as shown less overstability. (Any breeze and the Alpha weathercocks and you loose peak altitude.)
* Like to see a Big Berthas in altitude competitions...lol

 

[CrocketRocket]

Between you two options. I would go with the Modified Big Bertha.
* as shown less overstability. (Any breeze and the Alpha weathercocks and you loose peak altitude.)
* Like to see a Big Berthas in altitude competitions...lol

I'm new to rocketry . . . after a 30 year break from doing it when I was in middle school. Hmm. . . so over stability does not actually guarantee more vertical straighter flight, but is actually a possible weakness with wind? I hadn't thought about that before. I'll have to research ideal stability ratios.

I also like the idea of Big Bertha in an altitude competition. It sends the message: "I'm going to go high DESPITE using a Big Bertha!". Plus I'll be able to keep eyes on it better. Thanks.

 

[CrocketRocket]

I will aim for 1.5 to 1.9 range stability.

 

[Tractionengines]

Very simply:
Not enough stability and bad flight. (Loops, skyright, nose over into ground etc.)
Too much and you weathercock into the wind. if long-slow boost, can lead to gravity turn and rocket will not reach max height, but have significant horizontal velocity at apogee.

 

[3stoogesrocketry]

Im doing a Estes DoorKnob on a 54mm I. The rocket was 20 ish , the extra parts 30 ish , motor was 50 bucks. So for about 100 bucks I have a 7500 foot flight to just over mach . A G75 puts this to 3000 foot

 

[Tractionengines]

I will aim for 1.5 to 1.9 range stability

I would say that is a good start.

 

[CrocketRocket]

Can it be scratch built and use electronics for deployment? If so a 24mm minimum diameter on a CTI G65W. Projected altitude 9K.

9,000 ft! WOW! That is incredibly high altitude!

You can use electronics for deployment, as long as you don't go over the $100 budget. Plus the engine cost has to be included in that $100 budget. If you want to do minimum diameter . . . you'd also have to select a 24mm diameter Estes kit as your base model, but then you can extensively modify from there.

Would the classic Estes Alpha 24mm diameter be a good base start?

Thank you for the heads up on potential awesomeness of a G65W motor!

 

[CrocketRocket]

Im doing a Estes DoorKnob on a 54mm I. The rocket was 20 ish , the extra parts 30 ish , motor was 50 bucks. So for about 100 bucks I have a 7500 foot flight to just over mach . A G75 puts this to 3000 foot

54mm! I'm sooo new to rocketry 54mm isn't even on my radar screen. Great to know its an option though!

 

[3stoogesrocketry]

54mm! I'm sooo new to rocketry 54mm isn't even on my radar screen. Great to know its an option though!

It's built around a Aerotech SU 1280ns J700 BT. Mach 2 and 12k feet , if it hold together

 

[dhbarr]

9,000 ft! WOW! That is incredibly high altitude!

You can use electronics for deployment, as long as you don't go over the $100 budget. Plus the engine cost has to be included in that $100 budget. If you want to do minimum diameter . . . you'd also have to select a 24mm diameter Estes kit as your base model, but then you can extensively modify from there.

Would the classic Estes Alpha 24mm diameter be a good base start?

Thank you for the heads up on potential awesomeness of a G65W motor!

Skywriter would be a better base kit IMO just for the nosecone, but you'd need to scratch build new fins either way as a g65 will easily punch through M1 at minimum diameter. There's also the matter of not losing it....

 

[CrocketRocket]

Yes. The Sky writer is only $15 and you get two body tube lengths to work with.

Bonus, Sky Writer's long pointy nose cone = actually useful if punching through Mach 1

 

[Alan15578]

Fools! You only want o fly to about 2700 feet. Anything more is counter productive.

 

[ghostfather]

Here's my entry based on the Estes Skywriter and a 24mm CTI G65 White Longburn. I've shortened it and replaced the fin can with 3D printed fins, and put in a streamer and electronics.

Sims to 7500 ft and Mach 1.05.

• Estes Skywriter kit $15
• CTI G65 White Longburn $31
• Kevlar shockcord $3
• Nylon streamer $5
• 3D printed fins $1 filament cost
• 6 grain 24mm casing $28
• 24mm closure $15

Total $98 exclusive the electronics

Would probably try an eggtimer mini GPS in the nose, and an eggtimer apogee altimeter for pushing the streamer out at apogee.
Would also be using friction fit for the casing, and a fly-away launch lug system.

 

[CrocketRocket]

If using a CTI motor, does the cost of the casing and closure count towards the $100 budget?

Yes.

The total cost of the ENTIRE rocket build cannot exceed $100. If those casings are expensive and blow the budget . . . then, they are not a viable option for this competition.

The rocket would be disqualified.

 

[CrocketRocket]

Fools! You only want o fly to about 2700 feet. Anything more is counter productive.

Alan brings up a good point. 5000 feet, 7000 feet, 9000 feet are all impressive numbers. But those super high altitudes add risk of losing track of the rocket. A rocket not found = a rocket that can't win.

2,700 feet would win.

Personally, I like 3,000 feet as a good altitude target. Leaving some buffer in case the competitors get smart, or fly a bit higher.

A rocket that flies 2,500 feet would also win, but risky, because it might not have a perfect flight, (too close to the other competitors performance capabilities).

A mile high flight = puts a nice aggressive smackdown on the competition, but adds recovery risk.

 

[CrocketRocket]

Yes.

The total cost of the ENTIRE rocket build cannot exceed $100. If those casings are expensive and blow the budget . . . then, they are not a viable option for this competition.

The rocket would be disqualified.

Only the cost of altimeter is excluded from the $100 rocket build budget.

 

[ghostfather]

aha, then I couldn't put in a gps unit unless it's combined with the altimeter.
If mine flies to 7500 ft it should come down about 1/4 mile from the pad using the slightly breezy settings in my sim. I'd probably risk it, depending on the weather.

For me it's an exercise in minimum diameter design. 3000 ft is too easy.

 

[CrocketRocket]

aha, then I couldn't put in a gps unit unless it's combined with the altimeter.
If mine flies to 7500 ft it should come down about 1/4 mile from the pad using the slightly breezy settings in my sim. I'd probably risk it, depending on the weather.

For me it's an exercise in minimum diameter design. 3000 ft is too easy.

Ghostfather,

Your Skywriter build is an impressive candidate. Totally plausible. You stayed within budget. Huge altitude. Detailed response. A true David versus Goliath. . . Wolf in Sheep's clothing.

 

[ghostfather]

BTW, the present Tripoli G record is 8796 ft.
I'd be interested in seeing Aaron's scratch built design that can get to 9K, just from "professional interest", though it's outside of the rules of this hypothetical competition. I've been bitten by the altitude bug a few years ago (people say it'll pass).
My best scratchbuilt G altitude rocket sims to just north of 8K, and has yet to be flown.

 

[ghostfather]

Wolf in Sheep's clothing

Reminds me of a trick car I saw back in the 70's, where someone removed the engine and rear seat of a VW Beetle, and dropped in a small block V8 and air shocks. He had it rigged so that it sounded pretty tame, back in the time when some people were racing VW Beetles anyway. He'd flip a switch, the air shocks would elevate it to "racing stance", and the exhaust disconnected from the mufflers (became straight pipes). Supposedly all street legal, though I saw it at a racing strip.

Now THAT was a wolf in sheep's clothing.

 

[dhbarr]

BTW, the present Tripoli G record is 8796 ft.
I'd be interested in seeing Aaron's scratch built design that can get to 9K, just from "professional interest", though it's outside of the rules of this hypothetical competition. I've been bitten by the altitude bug a few years ago (people say it'll pass).
My best scratchbuilt G altitude rocket sims to just north of 8K, and has yet to be flown.

g65's sim extremely high, but the proof will be in getting it not to precess. Experts remain divided as to whether off-center mass or off-angle thrust ( or some combination thereof ) causes this coning, but it does rob a fair bit of altitude.

 

[sandeja1]

This is a really interesting idea to me! I don't have anything to add other than I am enjoying reading the responses (entries?) and will have to see if I can come up with something as well! Thank You for posting this "brain teaser"!

 

[Nytrunner]

g65's sim extremely high, but the proof will be in getting it not to precess. Experts remain divided as to whether off-center mass or off-angle thrust ( or some combination thereof ) causes this coning, but it does rob a fair bit of altitude.

I just want him to tell us how fast it goes on the G145 or G152

 

[ghostfather]

I just want him to tell us how fast it goes on the G145 or G152

My sim using the CTI G145 Pink only reaches 7000 ft, and travels at Mach 1.25
My sim using the CTI G150 BlueStreak reaches 7200 ft, and travels at Mach 1.27
couldn't find a G152 motor designation on Thrust Curve
My sim goes highest on the CTI G65 White Longburn, reaching 7500 ft at Mach 1.05
All three motors have a similar Impulse on the top end of thr G class

Velocity and max-G is interesting as far as building, but this was a hypothetical altitude competition. Often a regressive slow burning motor of the same impulse will achieve a higher altitude, partially because velocity (and thus the drag) is lower

g65's sim extremely high, but the proof will be in getting it not to precess. Experts remain divided as to whether off-center mass or off-angle thrust ( or some combination thereof ) causes this coning, but it does rob a fair bit of altitude.

Precession sounds interesting, and as you mention it being caused by off-center mass or off angle thrust (caused by an off-center slotted grain), it sounds plausible, and worth looking into to try to understand it. Looking at the equations, I'm not sure where to begin to quantify it's effect.
Are there estimates or rules of thumb as to how big the effect is, resulting in ? % altitude reduction? If it's less than 5%, that's within the expected variations of thrust on the manufactured motors, and hard to quantify
Always something new to learn about, thanks

 

[dhbarr]

Precession sounds interesting, and as you mention it being caused by off-center mass or off angle thrust (caused by an off-center slotted grain), it sounds plausible, and worth looking into to try to understand it. Looking at the equations, I'm not sure where to begin to quantify it's effect.
Are there estimates or rules of thumb as to how big the effect is, resulting in ? % altitude reduction? If it's less than 5%, that's within the expected variations of thrust on the manufactured motors, and hard to quantify
Always something new to learn about, thanks

g65's a moonburner -- and one needs a 24mm altimeter as the max delay isn't nearly long enough

I've heard up to 10%, but haven't seen any proofs.

 

[CrocketRocket]

Here are photos of the rockets you'll be up competing against.

 

[CrocketRocket]

Reminds me of a trick car I saw back in the 70's, where someone removed the engine and rear seat of a VW Beetle, and dropped in a small block V8 and air shocks. He had it rigged so that it sounded pretty tame, back in the time when some people were racing VW Beetles anyway. He'd flip a switch, the air shocks would elevate it to "racing stance", and the exhaust disconnected from the mufflers (became straight pipes). Supposedly all street legal, though I saw it at a racing strip.

Now THAT was a wolf in sheep's clothing.

VW "Wolf in Sheep's Clothing"

I know exactly what you mean. In 1969, famous race car driver Emerson Fittipaldi needed a cheap race car on short notice for a huge endurance race in South America. Tight on time and budget, his team just added a second engine to a VW bug! Amazingly, the VW bug was successfully able to maintain 3rd place, while competing against Ford GT40s, and other impressive looking race cars. After an hour of racing, the gearbox died. Still an amazing feat. I love that story.

Here is a picture of the VW bug in the race.

 

[CrocketRocket]

For this competition, I think the competitors did not understand fundamentals of rocketry. From their rocket kit choices, they seemed to think that "bigger means better", or at least "the bigger the rocket the higher it goes". Some of those rockets are huge, and probably pricey too!

So I think any competitor walking up to the launch pad with a diminutive Estes based kit, probably would have been laughed at. . . until the Estes rocket launches and surprises everyone by winning the competition.