7/15/09

Name for "Untitled"

by DTH Rocket

Because of Saturday's major disaster, I thought of a name that should suit this rocket. "Double-Trouble" is indicative of its double-stage characteristic, not to mention its miserable life-story.

2 comments:

Rachel Kimberly said...

I like it!

July 16, 2009 at 9:21 PM
High Power Rocketry said...

Re stage ratios:

You would be better off consulting experts or a rocketry book for the exact reasons, but I do think that 4:1:.25 is a good impulse ratio, in a rule of thumb on our scale. Large rockets, space rockets, have so many other concerns that they seldom meet any specific ratio. Having said that, the Saturn V had about a 3:1 stage ratio from stage 1 to 2.

This is a very common ratio in smaller rockets, as well as in the hobby. It probably makes sense to make each upper stage comparable in mass to an optimum mass boosted dart. By this, I mean you want the mass of the next stage to be far lighter than the lower stages because the whole idea is to get the most of a lower stage motor, but then lose as much mass as possible, maintaining a high mass fraction with each stage even stage 1. Also, this allows for a reduction in diameter and drag with each stage. If you have a 4 inch O motor staged to a 4 inch O motor... you lose very little mass after staging, and maintain the high drag. This rocket would go very high indeed (a well designed rocket like this could hit 100,000 feet), but I am not certain if it would go as high as an O staged to a 2 inch M! And that is with several M's fewer impulse. It certainly wouldn't go as high as an O to an M to a K. But that adds the confounding factor of 3 stages.

There is no reason why a rocket that goes from a K to a K or O to an O wouldn't perform well. But there is plenty of reason to think that they are less than optimal.

If you investigate this further, I would love for you to put my somewhat unscientific hunches to the test and get back to us over at highpowerrocketry about your results. It is quite possible that I have been missing the point here. But that is the fun of science!

-R2K

July 19, 2009 at 9:49 AM

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