# Velocity and altitude.

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##### Active Member
With the rocket I'm building right now, I can't go above a C6 and I doubt if I'll ever go beyond a D12 with any build. Get's too expensive.
So, I'm designing with the assumption I'll be well below supersonic.
Assuming a light, well designed rocket, anybody have an idea of how fast a C6 or D12 powered rocket will go?
How big would I have to go to go supersonic? Would an F get me there?

Also, I read something that gave me the impression that the more powerful motor isn't necessarily the one that gives you the most elevation because the higher the speed the greater the drag. So a low output, long burning motor is better.
Or, put another way, assuming a light, well designed rocket, what B or C motor is likely to get me the most elevation?

I would think that the higher the rocket goes, the more likely you are to lose it. Do a lot of you go for more show than altitude? Is a big roar and lots of flame and smoke more important to you than going high?

#### dhbarr

##### Amateur Professional
Try one of the new c5's and a streamer. I think if you build minimum diameter, you'll have trouble getting it back even though it'll come down pretty fast.

Lots of folks find their fun in different ways to fly, from perfect scale reproductions of a specific flight up to a thousand miles an hour and 50k ft.

#### Alan15578

##### Well-Known Member
You should download Estes TR-10. After you have read that, you should play with the various computer programs.

The AT E50 has been documented to M1.1, and old AT F80 to M1.42. Some people claim an AT D21 could do M1.0.

Most people are like you, They fly low power motors to save money and hope to recover the rocket.

##### Well-Known Member
With the rocket I'm building right now, I can't go above a C6 and I doubt if I'll ever go beyond a D12 with any build. Get's too expensive.
So, I'm designing with the assumption I'll be well below supersonic.
Assuming a light, well designed rocket, anybody have an idea of how fast a C6 or D12 powered rocket will go?
NAR keeps track of altitude records, by motor:

C's have been recorded going upto 1209m (a tad under 4K feet).
D's require a larger diameter airframe, and are only recorded hitting 1214m.
Both went way higher than a naked eye can track, so finding them will be as much of a challenge as building and launching!

How big would I have to go to go supersonic? Would an F get me there?
Yes.

For yet more details, download an OpenRocket simulation program, and have a ball:

Also, I read something that gave me the impression that the more powerful motor isn't necessarily the one that gives you the most elevation because the higher the speed the greater the drag. So a low output, long burning motor is better.
Or, put another way, assuming a light, well designed rocket, what B or C motor is likely to get me the most elevation?
OpenRocket holds the answers you seek!

I would think that the higher the rocket goes, the more likely you are to lose it. Do a lot of you go for more show than altitude? Is a big roar and lots of flame and smoke more important to you than going high?
Do what makes you enjoy this hobby: go higher, find ways to track rockets in flight, way to record altitude, create more smoke, more sparks.
Just remember, as with most things in life, fun costs money.
How much can you afford?

#### DaveW6DPS

##### Well-Known Member
Altitude depends on a number of factors. Weight has less effect than drag. The best thrust profile for the motor depends on the design of the rocket. A lighter rocket doesn't always go higher, since the inertial increases as the mass of the rocket increases.

The Handbook of Model Rocketry is a great investment, and experimenting with Openrocket is much cheaper than experimenting with actual rockets.

##### Active Member
My original idea was to use an 18mm body tube with an 18mm motor, but decided it made installing and removing engines a hassle.
I figure it isn't likely I'd set any altitude records anyway, so go with convenience.
After this rocket, I might go tiny. I actually ordered some arrow vanes with the idea of using them on this rocket, but when they arrived, it was obvious they were way too small. Not sure if an 18mm body tube is small enough or I'd need to go to a 13mm, but it is obvious the vanes would be great on a small rocket.
I'm probably not into the scale model thing. My building skills aren't up to it. But I might go for a cool looking design, in the near future. I always thought the Honest John was a cool looking missile. I ordered a balsa nose cone of that design.
I'll try and get some good photos for you when the rocket is nearer completion. Right now I have fins on a body tube. I have nose cones, but probably not the one I'll end up using.
I designed the fins by finding a profile photo of the Boeing 777X and taking measurements.

#### David Schwantz

##### Well-Known Member
All of the above. I like speed, I have a 1/2 A size rocket that flies on an A10T, she is not even a blink of an eye and it's gone. Comes down on a streamer. I like altitude, long burns are great, but not always the answer. the more weight in the NC the higher she will fly, up to a point. You will loose performance after so much. I fly a lot of White Lightning motors, as I like to roar and the flame, and thrust. I liked two stagers as a kid, so I built 3 of them this past winter. But my most enjoyed is scale. Like putting on all the details, like painting them to match full size. Enjoy watching them fly, which most are low and slow. Nice things about this addiction, is there is something for everyone. Glad you made it, go pop a chute.

#### BABAR

##### Builds Rockets for NASA
TRF Supporter
There is a saying, or at least there should be

If you aim at nothing, you will probably hit it.

First, define the limits you select

How much are you willing to spend?

How far do you want to travel to launch (MicroMaxx often can be launched from your front yard, low power possibly a nearby park nearby —check your local laws, high power requires a waiver and for many if not most people will need a club to launch with, so how close is the club and how often do they launch). If you have a local low power field, how big is it? Saucers and some big fat or heavy low power rockets can be launched and more importantly recovered on small fields. As @afadeev notes, C and D motors in rockets optimally built for ALTITUDE can go over 1200 feet, you need a low wind day and a big field if you want to get them back. Not sure if trackers come that small, but if so look at spending big \$

Note I said For the most part YOU select those limits (although your income or significant other may also have some effect!)

Now select your goals, within the limits you set above.

If speed is your thing, and you have a small field, play with open rocket software. Maybe a 13 mm minimum diameter three fin rocket will be your best bet. I am not a speed demon, and as an observer I think the fastest rocket is probably the 13mm Mosquito, simply because it seems to “autotransport” instantaneously from the pad to the netherworld (often never to be seen again) at launch. Also, unless you have some fancy electronics on board, is most cases you don’t know how fast it really went. As for exceeding Mach, it is my understanding that for rocket models you rarely if ever hear the “sonic boom”, but if you have the equipment aboard to measure the speed and breaking Mach appeals to you (it is an accomplishment to build a rocket light enough to get to that speed, strong enough to handle the speed, and hopefully RECOVER it, but may be limited by your budget and field size.)

If maximum altitude is your goal, you definitely need a big field.

Note that in the above when I mentioned “optimally built for ALTITUDE”, I meant just that. There is no true generally “optimally built” rocket, only rockets that may be “optimally built” for a certain goal. For you, the “optimally built” rocket (or more likely rocketS) are the ones that give you the most satisfaction. Model Rocketry is wide open with options, not just in size, buy also
speed,
altitude,
duration,
recovery methods including parachute, streamer, glider, featherweight, tumble, horozontal spin, airbrake (please avoid BALLISTIC!)
Scale modeling
finish (mirror like to nekkid)
OddRocs (flying portapotties, traffic cones, plastic human skeletons, tapeworms)