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OpenRocket

openrocket.info

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Re: OpenRocket

#121

Post by GordonS »

hermitcrab wrote: post #120
GordonS wrote: post #117

Earlier quoted context omitted.

Heh, UK tinkerer here :) How hard is it to get started for amateurs? Are rules/regulations problematic?

Not hard. Buy an Estes kit. Go along to one of the regional meetings, fly your rocket and talk to people there - they are very friendly. The UK regulations are fairly sensible and they won't let you do anything stupid at one the regional meets. Just start with something small (A/B/C motor) and work your way up from there. Don't try to start with a K motor, 2 stage or liquid propellant and you'll be fine. Where are yo…

Thanks, I'm in NE Scotland.

Re: OpenRocket

#122

Post by joelshep »

stackedinserter wrote: post #53
joelshep wrote: post #44

Earlier quoted context omitted.

But hopefully not that kind of interest. Model rocketry, as a hobby, enjoys a limited amount of regulation, at least in the US. In large part, that is because the community has been very good about self-policing. Most folks who are serious about the hobby closely follow the safety guidelines published by the two national organizations (Tripoli and NAR), and steer newcomers to as well. Serious accidents are few and fa…

Hobby rockets fall into the same regulations as drones.

Not true in the US either, in any meaningful way. Weight thresholds are different, FAA thresholds are different, allowed control systems are different, etc., etc.

Re: OpenRocket

#123

Post by DetroitThrow »

sibovg wrote: post #80
_moof wrote: post #63

Software developers: I am begging you to put representative screenshots on the home page. This has become a real widespread problem. I know you want to tell us all about the amazing (sincerely!) stuff under the hood, but to users, the interface is the product.

Thanks for the suggestion, I've added it to our home page.

The product is much cooler than I thought. Great update.

Re: OpenRocket

#124

Post by hermitcrab »

GordonS wrote: post #121
hermitcrab wrote: post #120

Earlier quoted context omitted.

Not hard. Buy an Estes kit. Go along to one of the regional meetings, fly your rocket and talk to people there - they are very friendly. The UK regulations are fairly sensible and they won't let you do anything stupid at one the regional meets. Just start with something small (A/B/C motor) and work your way up from there. Don't try to start with a K motor, 2 stage or liquid propellant and you'll be fine. Where are yo…

Thanks, I'm in NE Scotland.

See:

https://www.sara.rocketry.org.uk/

https://ukra.org.uk/links/uk-clubs/

https://irw.rocketry.org.uk/

Re: OpenRocket

#125

Post by sandworm101 »

hermitcrab wrote: post #119
sandworm101 wrote: post #108

Earlier quoted context omitted.

They also seem to be treating rockets as rigid bodies. Flex of parts is real at these accelerations but the calculations get into supercomputer territory very quickly. All the math is questionable if, at any given moment, your rocket isnt actually straight. Look into the physics of archery, which has similar accellerations albeit of a narrower tube. The choice between a heavier/stronger arrow v a lighter/flexible sha…

If your rocket is flexing significantly, then it probably won't be a rocket for very long!

Shuttle was held on the launch pad after ignition for a couple seconds because of flex. The stack initially flexed out of alignment when the main engines were lit, the stack being asymetrical. Only once the nose drifted back to vertical would the srbs ignite and the stack begin to move.

Re: OpenRocket

#126

Post by hermitcrab »

sandworm101 wrote: post #125
hermitcrab wrote: post #119

Earlier quoted context omitted.

If your rocket is flexing significantly, then it probably won't be a rocket for very long!

Shuttle was held on the launch pad after ignition for a couple seconds because of flex. The stack initially flexed out of alignment when the main engines were lit, the stack being asymetrical. Only once the nose drifted back to vertical would the srbs ignite and the stack begin to move.

OpenRocket is intended for amateur rocketry, not NASA space shuttles.

Amateur rocketry people try very hard to make their rockets symmetrical.

Hobby rockets have to be stiff enough not to banana. I don't think it is figured into model rocketry beyond that.

Re: OpenRocket

#127

Post by joelshep »

alexpopow wrote: post #95

What about misuse for weapon development? Does the project not massively cut R&D costs (hence lowering the entry hurdle) for potentially malicious actors on the planet?

You can buy the Handbook of Model Rocketry and have essentially all the knowledge that's encoded in OpenRocket or RockSim. You just lack the automated simulations and the parts catalogs (whose weights and dimensions should generally be double-checked anyway). The rockets designed by these programs assume static stability. If you want guidance of some sort, that is entirely on you: that's not remotely a capability available in these programs. If you want to launch at a funny angle, that's also entirely on you. If you want "accuracy" regardless of wind variations, motor variations, etc., that's entirely on you as well. There is a huge distance between the capabilities and the accuracy of simulations of programs like this, and what you would need to come close to developing an effective weapon.

Re: OpenRocket

#128

Post by plugger »

sandworm101 wrote: post #108
plugger wrote: post #78

Earlier quoted context omitted.

> we found the maximum altitude estimates were about 15% too high. this often happens when the wrong rocket finish is selected. Everyone chooses a polished finish when in actuality they've just sprayed the thing with paint. Skin drag is real.

They also seem to be treating rockets as rigid bodies. Flex of parts is real at these accelerations but the calculations get into supercomputer territory very quickly. All the math is questionable if, at any given moment, your rocket isnt actually straight. Look into the physics of archery, which has similar accellerations albeit of a narrower tube. The choice between a heavier/stronger arrow v a lighter/flexible sha…

Not really applicable here imho. Most high power high performance rockets aren't cardboard. The majority are either fibreglass or carbon fibre.

Flex doesn't really become a concern with carbon fibre until you approach Mach 3. I say this because I've built two rockets of an identical design philosophy; one for 54mm motors and one for 75mm motors. The 54mm motor rocket did M2.64 and I could fly it again today if I wanted. The 75mm rekitted itself at M3. It failed where I'd not reinforced the hand rolled airframe that I was flying. 4 wraps of 2x2 200gsm twill CF. Same number I used on the 54mm fine.

For both of these rockets the vast majority of the airframe is directly over a aluminum motor casing that is a rigid body. These things are grossly over-engineered when compared to the pressures/forces they see.

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