Welcome to the Water Rocket Forum, sponsored by The Water Rocket Achievement World Record Association.

The largest, most sophisticated and ground breaking group supporting you, the serious water rocket flyer! Whether you are a beginner or an expert, the WRA2 has something for everyone.

A water rocket is a type of model rocket using water as its reaction mass. The pressure vessel (the engine of the rocket) is constructed from thin plastic or other non metallic materials (usually a used plastic soft drink bottle) weighing 1,500 grams or less. The water is forced out by compressed air. It is an example of Newton's third law of motion.

Radar Altitude Measurement?

Discussion about deployment systems including altimeters, timers, air speed flaps, servo systems, and chemical reactions.
Post Reply
User avatar
Spaceman Spiff
WRA2 Member
WRA2 Member
Posts: 681
Joined: Sat Feb 24, 2007 11:06 am

Radar Altitude Measurement?

Post by Spaceman Spiff » Tue Jun 16, 2009 9:08 pm

Has anyone considered using radar to measure their rocket altitude? I ran across this neat toy and thought it might have some application in water rockets.



Spaceman Spiff
"What goes up, must come down"

User avatar
rockets-in-brighton
Senior Member
Senior Member
Posts: 431
Joined: Fri Jun 20, 2008 12:33 pm

Re: Radar Altitude Measurement?

Post by rockets-in-brighton » Wed Jun 17, 2009 2:43 am

Spaceman Spiff wrote:Has anyone considered using radar to measure their rocket altitude? I ran across this neat toy and thought it might have some application in water rockets.

It is a working speed gun, but how would you use it to measure altitude?


Cheers
Steve
Rockets-in-Brighton
WEB: http://groups.google.co.uk/group/rockets-in-brighton

User avatar
Bonami
Advanced Member
Advanced Member
Posts: 94
Joined: Tue Apr 10, 2007 9:10 am

Re: Radar Altitude Measurement?

Post by Bonami » Wed Jun 17, 2009 8:30 am

Spaceman Spiff wrote:Has anyone considered using radar to measure their rocket altitude? I ran across this neat toy and thought it might have some application in water rockets.

I've seen these in action and they really do work. I saw some guys timing themselves downhill skiing with one and the thing was actually working! The problem with using them for rockets is the range is pretty short. I don't think you would be able to detect a tiny rocket from far below.



User avatar
Spaceman Spiff
WRA2 Member
WRA2 Member
Posts: 681
Joined: Sat Feb 24, 2007 11:06 am

Re: Radar Altitude Measurement?

Post by Spaceman Spiff » Wed Jun 17, 2009 10:30 am

rockets-in-brighton wrote:
Spaceman Spiff wrote:Has anyone considered using radar to measure their rocket altitude? I ran across this neat toy and thought it might have some application in water rockets.

It is a working speed gun, but how would you use it to measure altitude?
I'm sorry. I forgot to put this link in my original post: http://www.edparadis.com/radar/

It looks like people a lot smarter than me have figured out how to hack this toy and make improvements. I think someone could easily convert the thing to measure distance, do you agree? I think that would be a great way to measure altitude.


Spaceman Spiff
"What goes up, must come down"

User avatar
rockets-in-brighton
Senior Member
Senior Member
Posts: 431
Joined: Fri Jun 20, 2008 12:33 pm

Re: Radar Altitude Measurement?

Post by rockets-in-brighton » Wed Jun 17, 2009 12:32 pm

Spaceman Spiff wrote: It looks like people a lot smarter than me have figured out how to hack this toy and make improvements. I think someone could easily convert the thing to measure distance, do you agree? I think that would be a great way to measure altitude.
I see what they are doing. It did look as though the power would be too low to measure anything much beyond 30m, especially when the target would be small and hard to pick up (no metal parts, unless you add some metal foil or similar.) Perhaps an external dish would help?


Cheers
Steve
Rockets-in-Brighton
WEB: http://groups.google.co.uk/group/rockets-in-brighton

User avatar
Team Seneca
WRA2 Member
WRA2 Member
Posts: 242
Joined: Sun Dec 31, 2006 1:40 am

Re: Radar Altitude Measurement?

Post by Team Seneca » Wed Jun 17, 2009 2:17 pm

I played around with this idea last summer. My conclusion was that you could probably get it to work if you covered your rocket in foil and had a clear day with no clouds. To get around various contest rules that prohibit metal on the tank structure I had an idea of using aluminized mylar for the parachute.

You would not see the rocket ascend but the parachute deploy would give you the peak altitude and descent rate. A large chute would reflect quite a lot of the signal.

It's a neat idea but I never got excited enough to try it out.


Bill W.
Team Seneca

Blake [B&R Rocketry]
WRA2 Member
WRA2 Member
Posts: 8
Joined: Sat May 16, 2009 2:29 am

Re: Radar Altitude Measurement?

Post by Blake [B&R Rocketry] » Thu Jun 18, 2009 12:28 am

Spaceman Spiff wrote:
rockets-in-brighton wrote:
Spaceman Spiff wrote:Has anyone considered using radar to measure their rocket altitude? I ran across this neat toy and thought it might have some application in water rockets.

It is a working speed gun, but how would you use it to measure altitude?
I'm sorry. I forgot to put this link in my original post: http://www.edparadis.com/radar/

It looks like people a lot smarter than me have figured out how to hack this toy and make improvements. I think someone could easily convert the thing to measure distance, do you agree? I think that would be a great way to measure altitude.
I believe radar guns work by measuring the time it takes for the signal (photons) to go the object and back, they then take two of these measurements at a set time interval and can determine the change in distance with respect to time, or velocity. So to measure just distance you would just need the round trip time. You then take this time divide it by two (since the time is the the rocket and back) and times it by the speed of light in air (2.99879x10^8 m/s) to get the distance in meters (d=v*t).

What if you put the sending unit on the rocket and had a big reflector on the ground? This might help the aiming issue.



User avatar
Andromeda
Senior Member
Senior Member
Posts: 144
Joined: Thu Feb 01, 2007 4:21 pm

Re: Radar Altitude Measurement?

Post by Andromeda » Thu Jun 18, 2009 2:07 am

Blake [B&R Rocketry] wrote:What if you put the sending unit on the rocket and had a big reflector on the ground? This might help the aiming issue.

Won't the ground act like a huge reflector by itself? If that would work then even if you don't get a accurate altitude reading you at least can tell that the rocket turned upside down and deploy a parachute when the earth disappears from the view of the antenna.


Andromeda
No matter where you go, there you are.
- Buckaroo Bansia

User avatar
Tim Chen
WRA2 Member
WRA2 Member
Posts: 871
Joined: Wed Jan 31, 2007 1:44 am

Re: Radar Altitude Measurement?

Post by Tim Chen » Thu Jun 18, 2009 10:55 am

Andromeda wrote:
Blake [B&R Rocketry] wrote:What if you put the sending unit on the rocket and had a big reflector on the ground? This might help the aiming issue.

Won't the ground act like a huge reflector by itself? If that would work then even if you don't get a accurate altitude reading you at least can tell that the rocket turned upside down and deploy a parachute when the earth disappears from the view of the antenna.
If all you need to do is deploy a parachute an electronic timer or magnetic sensor would be better (smaller, lighter, cheaper).


Tim Chen
Captain, Team Enterprise

The Mooseheads
Site Admin
Site Admin
Posts: 146
Joined: Sun Dec 31, 2006 2:08 am

Re: Radar Altitude Measurement?

Post by The Mooseheads » Thu Jun 18, 2009 9:53 pm

Honestly, I believe you can triangulate the altitude of the rocket using marks on the ground and a camera on the rocket. Bear in mind that you can't use one of those VGA resolution cameras if you expect to get accurate readings. You need a decent resolution sensor and there are a lot of good still cameras for under $100 that have 10-12 megapixels that would give great resolution.

If you put a pait of IR lamps on the ground at a predetermined distance pointing UP then you would get a really good pair of reference points. Take the IR filter out of the camera lens and out in an optical filter and you'd get super accurate reference points.

I got the idea taking apart the Wii controller to see how it works. Yes, they triangulate the position of the controller this way and it's quite accurate.


Rick C.
The Mooseheads

Post Reply