Some General Questions

[Blaze]

Hello, just some quick Qs:

1. How much does it cost to fire a rocket to different altitudes? (eg 1000ft = £5 for motor, £5 to build the rocket)

2. If you tilt the fins on a rocket, how would the spin affect the flight?

3. How much weight can (feasibly) be lifted with E to G size motors?

Thanks!

[BartDoe]

There are no concrete answers but since nobody else has replied, I'll throw out some off the cuff rules of thumb:

1.) You can get to 1,000 feet for under $10 US with standard Estes rockets and motors. 5,000 feet easily with MPR/HPR rocketry ($50)...10,000 feet you're getting serious..., bare minimum...$75...more like $150+ (that's probably a bit high in price). BUT...it depends ENTIRELY on what you use for materials and what you use for propellant...commercial or research...buy or borrow motor casings...fiberglass or kraft airframes...etc...and the goals of your flight.

2.) Up to a point, it makes a rocket more stable but it adds drag. Past that point the fins provide something else entirely (instability, I'd imagine). That is my (layman idiot) understanding of it...lots of real engineers here who could better answer.

3.) An Estes D will lift 12 ounces, barely...but unless it's an Estes kit most RSOs will frown on it. Assume 8-10 oz comfortably for a D12...in theory you could double that for each letter grade up but in practice it doesn't really work. So figure:

D up to 12oz
E up to 16oz
F up to 24oz
G up to 48oz

AGAIN, it *depends* on the engine...an E6 isn't going to lift 16oz and an F240 can safely lift a lot more than 24oz. Some Gs are listed as barely able to lift a single pound (16oz). And the Aerotech G339 will easily lift more than five pounds.

This URL has a lot of discussion about liftoff weights and rules of thumb - read it - http://www.rocketryforumarchive.com/...ad.php?t=32741

And this list on Apogee has maximum liftoff weights for single use Aerotech MPR (E-G) motors:

http://www.apogeerockets.com/aerotech_motors.asp

Hope that helps.

[JStarStar]

Our UK correspondents (Astro-Baby is one) report prices are somewhat higher in the UK. Mid-power rocketry (meaning altitudes over about 2000 ft) is definitely a significant jump up in investment.

I would say as a general rule that tilting fins on a rocket will NOT improve stability, unless the angle of tilt or deflection is carefully planned you are likely to get into pitch-roll coupling and "coning" problems (discussed on other threads) which can be disastrous for stability, so on any kind of "beginning" rocket (more accurately, anything less than 'advanced'), I would probably prefer to keep the fins as straight as possible and try to produce a straight flight rather than a spin.

[Astro-Baby]

Well I cant really say or speak for suppliers but if you took a look at a UK vendor you would get an idea.

SEMROIC SLS Hustler - cost (inc shipping) £40

Motor for above, heights and cost - cost doesnt include shipping which in the UK for the motors generally costs about £15 for a courier so if you order more/less it can have a big effect on final price. The price below is based on the cost of a pack of motors split down pro rata.

D12-3 350' (at a push) £4.60 per motor
D15-4 450' £7.00 per motor
E15-4 1,100' £9.50 per motor
F24-7 1,400' £10.50 per motor

That averages at about .9 pence per foot of altitude for tjose with a math mind. Above 1,400' I havent calculated because we all know that flying higher than that will cause the basic structre of the universe to crack and we'd all be swallowed up

[tightwad]

All the above reponses are very good and should give you an idea of costs, but, when you are pushing a 1000 ft , or greater, you better have a large area for recovery and be prepared to do some walking. Any tree in your recovery area will reach out and grab your rocket, no rocket is worth a broken neck. Good luck and enjoy this great sport.

[Blaze]

Thanks for the answers. Im just starting to get into rocketry and might try doing a project on it in a couple of years, but im going to start small!

[Andy Severn]

Actually, I'm pretty impressed with the prices of Estes motors in the UK (apart from the shipping costs, of course) might be worth a stab at trying some out sometime soon once I've kicked my sugar motor addiction!