20 replies to this topic

[Zero]

Okay, chemistry question!!!! (and I haven't even the slightest idea what to do as I haven't taken it yet!!!!!!)!!!!! I NEED to know, if you put a rocket in water, would:

A: A slingshot/catapult system be effective? I guess not since water tends to absorb so much of the energy and all the energy is released in one blow....

B: Would a railway system be effective? I need it to keep the rocket going straight....

C: What chemicals make a very powerful reaction when combined (think baking soda+ vinegar but with fifty times the punch (not literally)) I need a reasonable amount of thrust, to be able to move it five/seven feet in the water with only a few ounces of fuel while underwater.

D: Would I need any kind of overhead guidance system?

E: If I squeeze a relatively large amount of air through a small opening (such as a tube), would it have downsides? And if I slowly funneled it to make the output bigger in size than the intake, would it help?

F: I'm thinking of using the MiG (huge middle hole all the way through) approach, and working around it to accommodate the fuel (add a "skirt" to the bottom half of the rocket's body to make up for the shortened fuel storage.

G: If I made used the MiG approach, but kept the fuel space (in other words half-way through there's a stop) but then added small openings along the side to expel the air (would be angled down and angled) would that work?

Any Ideas?

Also, could I get a definitive formula for thrust?

Edited by tskasa1, 05 November 2008 - 00:18.

[Sgt. Rho]

What do you mean with put a rocket in water? Do you mean like a nuke sub firing a missile out of the water? Gas pressure and a gas sapsule that creates a sort of bubble arround the rocket would be best.

[Chyros]

Quote

What do you mean with put a rocket in water? Do you mean like a nuke sub firing a missile out of the water? Gas pressure and a gas sapsule that creates a sort of bubble arround the rocket would be best.

That. I have no idea what you're trying to make exactly XD. I could answer the following however:

tskasa1, on 30 Oct 2008, 2:58, said:

C: What chemicals make a very powerful reaction when combined (think baking soda+ vinegar but with fifty times the punch (not literally)) I need a reasonable amount of thrust, to be able to move it five/seven feet in the water with only a few ounces of fuel while underwater.

You'll need some sort of gas-liberating system to provide the thrust, which can either be the soda or an explosive. I assume you don't want to make an explosive (you'd basically blow whatever you're building out of the water instead of giving it gradual thrust) so the soda thing might be best for you. Things to optimise the amount of thrust this provides is using more concentrated and/or higher amounts of reactants (i.e. don't use baking powder but pure NaHCO₃), or use washing soda (sodium carbonate, Na₂CO₃) instead of baking soda (you might want to start out with smaller amounts of reactants since sodium carbonate generates heat during the reaction).

[Dauth]

Normally I would offer advice, but you've ignored my request and started a thread called "HELP!!!!" again.

You're on your own.

[Zero]

Dauth, on 30 Oct 2008, 9:41, said:

Normally I would offer advice, but you've ignored my request and started a thread called "HELP!!!!" again.

You're on your own.

Thanks, and I would have, but then I found out that this needs to have some sort of appliance in the near future, so anything that has no foreseeable use within the next 100 years it taboo. Thanks for the suggestion anyway, and I did think about using it, but it is impossible to use now, as my teacher doesn't want me to as it has no foreseeable use to benefit mankind (and yes it does HAVE to benefit mankind).

[Dr. Strangelove]

Ballistic Missile Subs(SSBNs) usually use pressurized CO2.

[Zero]

Dr. Strangelove, on 30 Oct 2008, 23:36, said:

Ballistic Missile Subs(SSBNs) usually use pressurized CO2.

How much thrust could I potentially get from it? Also, how easy and affordable is it? After all, I need to keep it all under one-hundred dollars. I like the idea and since it can move nukes it should do well, but again, I need to keep it all as cheap as possible.

Also, to answer all previous questions, yes, I AM planning to put a few rockets under water and launching them. I want to make holes in each one to see how it will affect them, whether it'll add aerodynamics (in other words, it should increase range/speed). I'm using water because it is a LOT harder to monitor it in the air and I don't have a wind tunnel, also water behaves a lot like air (save it is a LOT more... elastic for a lack of a better word). So, do any of the above ideas work, and still open to fuel ideas.

[Chyros]

tskasa1, on 1 Nov 2008, 0:59, said:

Dr. Strangelove, on 30 Oct 2008, 23:36, said:

Ballistic Missile Subs(SSBNs) usually use pressurized CO2.

How much thrust could I potentially get from it? Also, how easy and affordable is it? After all, I need to keep it all under one-hundred dollars. I like the idea and since it can move nukes it should do well, but again, I need to keep it all as cheap as possible.

Also, to answer all previous questions, yes, I AM planning to put a few rockets under water and launching them. I want to make holes in each one to see how it will affect them, whether it'll add aerodynamics (in other words, it should increase range/speed). I'm using water because it is a LOT harder to monitor it in the air and I don't have a wind tunnel, also water behaves a lot like air (save it is a LOT more... elastic for a lack of a better word). So, do any of the above ideas work, and still open to fuel ideas.

Easiest way to obtain something analogous to pressurized CO₂ is to get some canned air. If you really want CO₂ you're probably looking at using a fire extinguisher. Problem is getting a release mechanism for this. Also, generally commercially pressurized gases can be quite dangerous if not handled properly because if they really go, they really go.

[Dr. Strangelove]

tskasa1, on 31 Oct 2008, 23:59, said:

Dr. Strangelove, on 30 Oct 2008, 23:36, said:

Ballistic Missile Subs(SSBNs) usually use pressurized CO2.

How much thrust could I potentially get from it? Also, how easy and affordable is it? After all, I need to keep it all under one-hundred dollars. I like the idea and since it can move nukes it should do well, but again, I need to keep it all as cheap as possible.

Also, to answer all previous questions, yes, I AM planning to put a few rockets under water and launching them. I want to make holes in each one to see how it will affect them, whether it'll add aerodynamics (in other words, it should increase range/speed). I'm using water because it is a LOT harder to monitor it in the air and I don't have a wind tunnel, also water behaves a lot like air (save it is a LOT more... elastic for a lack of a better word). So, do any of the above ideas work, and still open to fuel ideas.

The only cheaper option than pressurized CO₂ or just plain old atmosphere would be a catapult(not an actual catapult, just any system that uses brute physical force to propel the missile.).

[Zero]

Umm... guys, how would I go about transferring a little bit of the CO2 from the fire extinguisher into the VERY small container I'll be using in my rocket.

[Dr. Strangelove]

tskasa1, on 1 Nov 2008, 1:21, said:

Umm... guys, how would I go about transferring a little bit of the CO2 from the fire extinguisher into the VERY small container I'll be using in my rocket.

Umm, let me clarify, SSBNs use the CO₂ to just get the missile out of the tube and above the water, the liquid rocket fuel is what actually gets it to the target.

[Chyros]

tskasa1, on 1 Nov 2008, 3:21, said:

Umm... guys, how would I go about transferring a little bit of the CO2 from the fire extinguisher into the VERY small container I'll be using in my rocket.

You can't. Once you decompress it, you'll have no means of recompressing it again. You the rocket needs to be the container or you'll need to make a reaction yourself.

[Zero]

Jason, on 1 Nov 2008, 11:13, said:

tskasa1, on 1 Nov 2008, 3:21, said:

Umm... guys, how would I go about transferring a little bit of the CO2 from the fire extinguisher into the VERY small container I'll be using in my rocket.

You can't. Once you decompress it, you'll have no means of recompressing it again. You the rocket needs to be the container or you'll need to make a reaction yourself.

So....if I use CO2, I'm fucked.... yeah, any other ideas? Help me out anybody? I wish I could use CO2.... damn it! I need cheap and powerful!

[Dr. Strangelove]

tskasa1, on 1 Nov 2008, 22:09, said:

Jason, on 1 Nov 2008, 11:13, said:

tskasa1, on 1 Nov 2008, 3:21, said:

Umm... guys, how would I go about transferring a little bit of the CO2 from the fire extinguisher into the VERY small container I'll be using in my rocket.

You can't. Once you decompress it, you'll have no means of recompressing it again. You the rocket needs to be the container or you'll need to make a reaction yourself.

So....if I use CO2, I'm fucked.... yeah, any other ideas? Help me out anybody? I wish I could use CO2.... damn it! I need cheap and powerful!

Buy the compressed oxygen tanks used for SCUBA gear, or compressed helium used in party balloons.

[Jok3r]

Cheaper way of getting it is in a paintball/airsoft/airgun cartridge/tank- you can pick one up at sports authority or dicks sporting goods, if your in NJ.
Swimmer

[Zero]

The prblem is that I'm only using a few ounces (at most a few pounds- sorry if it,s the wrong format) I need something nice and small. Also, I've decided on not using a full MiG design, I'll be using a MiG decsign on the top half and then let it out through vents (although water's "elasticity" IS areal big pain because if it weren't for that, I could just use a god damned catapult!!!!!!!!

[Rich19]

A rocket is the small scale you're describing sounds very impractical and not powerful enough. What about some sort of rotating propeller power if it's in water?

Edited by Rich19, 02 November 2008 - 14:50.

[Dr. Strangelove]

tskasa1, on 2 Nov 2008, 14:55, said:

The prblem is that I'm only using a few ounces (at most a few pounds- sorry if it,s the wrong format) I need something nice and small. Also, I've decided on not using a full MiG design, I'll be using a MiG decsign on the top half and then let it out through vents (although water's "elasticity" IS areal big pain because if it weren't for that, I could just use a god damned catapult!!!!!!!!

Now I have to ask: Hat in hell are you trying to make!?

[BeefJeRKy]

Dr. Strangelove, on 3 Nov 2008, 3:42, said:

tskasa1, on 2 Nov 2008, 14:55, said:

The prblem is that I'm only using a few ounces (at most a few pounds- sorry if it,s the wrong format) I need something nice and small. Also, I've decided on not using a full MiG design, I'll be using a MiG decsign on the top half and then let it out through vents (although water's "elasticity" IS areal big pain because if it weren't for that, I could just use a god damned catapult!!!!!!!!

Now I have to ask: Hat in hell are you trying to make!?

Apparently a model SLBM...

[Dr. Strangelove]

Scope, on 3 Nov 2008, 9:20, said:

Dr. Strangelove, on 3 Nov 2008, 3:42, said:

tskasa1, on 2 Nov 2008, 14:55, said:

The prblem is that I'm only using a few ounces (at most a few pounds- sorry if it,s the wrong format) I need something nice and small. Also, I've decided on not using a full MiG design, I'll be using a MiG decsign on the top half and then let it out through vents (although water's "elasticity" IS areal big pain because if it weren't for that, I could just use a god damned catapult!!!!!!!!

Now I have to ask: Hat in hell are you trying to make!?

Apparently a model SLBM...

You know you can buy those down at a hobby shop.

[Zero]

I can't just buy it because it needs to be very heavily customized. Also, I can't use a propeller because it's supposed to be a rocket. I WOULD use air, but I would need an air tunnel for what I want and no one wants to trust a 14 year old around one. Without an air tunnel it would be almost impossible to measure the turbulence. ANYWAY, even IF I could get an air tunnel I would rather use explosive materials for the test as fuels but I can't use anything of the sort, so I'm kind of restricted to soda and chemical reactions. Anyway, more questions:

A) Would a "de Laval nozzle" work under water?

B) Would the nozzle have to be made out of metal or could it be made out of wood as well.

C) Is 45 degrees a nice stable angle for cutting through air/water? If not, what is?

And to answer your question my dear doctor.... it's a secret....*evil laugh*

Oh, completely forgot, does anyone know where I can get some good wood? I need strong, nonporous, hardwood, capable of taking a lot of stress and that is light enough to be propelled by gas. Any ideas?

Edited by Dauth, 04 November 2008 - 15:40.