[roc-chat] Re: Initial Launch Power
- From: Gregory Lyzenga <lyzenga@xxxxxxxxx>
- To: roc-chat@xxxxxxxxxxxxx
- Date: Wed, 15 Jan 2014 13:55:53 -0800
On Jan 15, 2014, at 1:49 PM, Michael Klett <xsive.guy@xxxxxxxxx> wrote:
> I've spent just a minute or two trying to noodle this and have not made much
> progress and I'm not sure how I would solve the problem besides just using a
> huge motor...
>
> NAR recommends an initial thrust of 6 to 1 or 5 to 1 for a safe launch.
> Given a rockets weight how would you figure out the minimum size motor to use?
>
> For grins, let's assume that the rocket plus motor weighs 2 lbs. I know that
> a Newton is the force required to accelerate 1 kg 1 m/s^s. But saying I need
> a motor with 6 n of thrust (2 lbs is just about 1 kg and 6 x 1 is 6) is
> wrong. My 2 lb rocket won't fly well on an Estes A8 motor.
>
> If my sim says that I'm pulling 6 Gs or more off the pad with a particular
> motor and rocket combination would that be good enough?
>
> What am I missing in the equation. It seems like it should be obvious but
> I'm not seeing it.
>
> Thanks,
> Mike
Mike, the conversion factor is 1 Pound (force) = 4.448 Newtons.
So a 6 to 1 ratio for a 2 pound rocket requires 12 pounds = 53 Newtons. You
can look at the published thrust curve to see what a particular motor’s initial
thrust spike is.
- Greg
----------------------------------------------------------
Gregory A. Lyzenga <lyzenga@xxxxxxx>
Dept. of Physics, Harvey Mudd College (909) 621-8378
Claremont, CA 91711-5990 mobile (626) 808-5314
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