Advise on a science fair project involving the flight time of different propellents

[baracksimposter]

For a science fair project i am trying to figure out the flight time and characteristics of model rockets with different propellants, i was just wondering if anyone had any ideas on different propellants that might be a good idea and not very dangerous like cryogenic fuels.

And any ideas on the materials and a good way to stay safe?

[astropapi1]

KNO3 is a good propellant for this kind of stuff.

[lajoswinkler]

First of all, there are no safe rocket propellants or safe rocket engines. This particular field of technology and engineering presents additional dangers.

Alkali nitrates, perchlorates and sulfur for oxidizers.

Sugar, rubber, zinc for the reducers.

This is highly complitated thing you're trying to do for a simple science fair and I'm not talking about the dangers. What's your methodology?

[baracksimposter]

Well i was going to compare the altitude the model rocket would obtain using three different propellants, which i will have to measure and have a equal amount of each for every launch. Looking at it now i will use sugar and potassium nitrate, as the first propellant, thanks astropapi. As the second propellant i might use a black powder motor, and for the third im not completely sure about what i will use. And im still wondering what class of motor im going to use for the control.

[lajoswinkler]

Black powder? It detonates easily so be sure to use only cardboard tubes for the casing, or thinner plastic.

Use zinc and sulfur if you can find zinc.

You might use only rocket candy with various additives, too. It's less complicated, but then you have to make it all at once because that fuel is next to impossible to produce again in the same state, in amateur conditions.

Finally, you have to use lots of launches of the same thing and find an average value. Don't be tempted to do one test for each fuel. That's not science.

What's "equal amount"? Mass? Moles? Volume of compressed powder?

[baracksimposter]

Equal amount of Mass

[JakeGrey]

Whatever else you do, wear proper protective equipment and keep a fire extinguisher handy.

[Ralathon]

How do you plan to find the altitude the rocket reached? Flight time? Or an actual altimeter? Because a gust of wind could totally botch your results on this.

Might be an idea to just launch the motors facing down (properly secured obviously) and record their force and burntime with scales or something instead. That way you cut out a lot of aerodynamic problems.

[Nibb31]

This really isn't something that you could safely pull off on your own as a simple science fair event.

Maybe you could do a lecture about rocket propellants and it by launching a model rocket.

[lajoswinkler]

If you want to test rocket engines, don't fire them in rockets. That's not how they're tested. Strap them against a scale and record the procedure while you're at a safe distance. The best is to have a kitchen analogue scale with 5kg capacity. Later examine the video. Note the value on the scale for each frame and plot it against time. Given the fact such engines fire for less than 3 seconds, you don't have a lot of work to do if the framerate is 25fps.

Repeat the test at least five times times, find average values and then make the final graph.

Repeat everything with another fuel.

Don't use large batches of fuel and don't make large engines. Inform the neighbours because each ground test means lots of smoke and incredible noise.

[baracksimposter]

Quotes aren't working right now...

@ralathon: yea that seems like a better idea, getting rid of some variables would give me better results.

@nibb: We have groups of 3, and looking at it now we are probably going to do what ralathon said

[astropapi1]

Dude, be careful.

Don't wanna go to the hospital, do you?

EDIT: To quote, simply double click the quote button.

[baracksimposter]

no i dont want to go to the hospital

and thanks for all the constructive replys so far

looking at it now with the testing of the merlin 1D tests that happened a little while back seems like a good idea...

[baracksimposter]

EDIT: To quote, simply double click the quote button.

What happened to just clicking quote once?

[astropapi1]

What happened to just clicking quote once?

The same thing that happened to the editor box, or "inline editing". The forums are semi-broken.

[baracksimposter]

The forums are semi-broken

wow i need to get with the times XD

[Idobox]

You could try a mono-propellant design too.

Peroxide is not toxic, and should be relatively easy to find, but is still very dangerous and degrades with time. For the catalyst, platinum is expensive, but there are lots of cheaper, less efficient alternatives like manganese dioxide or potassium permanganate.

No idea how to start the reaction safely though.