New high power Rocket launch

[BowtieGuy]

Jeff, that last pic of the yellow rocket brings back old memories; I used to have one of those in the original 8" size back in the day.
I'm pretty sure that the one I had was an "Estes" kit. If I remember correctly, wasn't that the one that came back down without the need for a parachute?

Edit: I just checked the Estes site, and they still have a similar rocket to this day, they say it "tumbles" back to earth.

 

[Benm]

Why would a rocket fall back to the ground and supersonic speeds?

Surely the terminal velocity would be high if it fell in the perfect nose-down orientation, but even if it did, i wonder if terminal velocity could ever be supersonic near ground level for a normal rocket. Considering the fuel has been burned the density of the whole thing would not be that large at all.

Also for a re-usable rocket i'd presume they come down a lot slower, aided by a parachute, as a terminal velocity impact with the ground would damage them beyond being usuable again?

In any case, if the body is constructed of nonconductive material fitting a transmitter and antenna assembly would not be that problematic: A usable uhf antenna would only need to consist of some very thin (0.1 mm would be okay) copper strips fitted to the body.

 

[Seoul_lasers]

Why would a rocket fall back to the ground and supersonic speeds?

Surely the terminal velocity would be high if it fell in the perfect nose-down orientation, but even if it did, i wonder if terminal velocity could ever be supersonic near ground level for a normal rocket. Considering the fuel has been burned the density of the whole thing would not be that large at all.

Also for a re-usable rocket i'd presume they come down a lot slower, aided by a parachute, as a terminal velocity impact with the ground would damage them beyond being usuable again?

In any case, if the body is constructed of nonconductive material fitting a transmitter and antenna assembly would not be that problematic: A usable uhf antenna would only need to consist of some very thin (0.1 mm would be okay) copper strips fitted to the body.

You've got to be extremely careful here with the regulations. The metal body would mean that Radar would pick it up. We are actually pretty close to a Canadian Armed Forces Base.

To further your question about the speed of a rocket coming in without a parachute.

Rockets coming down ballistic from high up can reach speeds well in excess of 600Km/hr, especially the ones we are flying which are in the high power range.
a ~2Kg rocket that falls from approximately ~2000m altitude. According to the math on the java calc the rocket will have an impact velocity of (theoretically) 712.76 km/h. This is because there will be little to no air resistance/drag on the airframe body.
likewise, a rocket falling from 6000m will be travelling the same speed as a .22LR. (sonic) ~1234.54Km/hr.

No... it wouldn't... it's going to have drag. This will dramatically change the
speed of which the rocket will fall. At tops it might hit a velocity of 300-400Km/hr at most from higher than 6Km. since we are only dealing with 2Km
and not much more perhaps not much more than 180Km/hr would be possible.

Of course, the ideal is to have a bursting charge to blow out a parachute to slow the rocket down as soon as it passes its apogee. This happens 99.9% of the time,
however occasionally the rocket's pyro-time fuse (disposable rocket engine H,I,J series) fails to ignite the busting charge ( or the electronic alt. sensor such as on reloadables) fails. The whole rocket essentially becomes a very large and expensive lawn dart.
If it happens to be flying over a highway (not that it should be) or houses eek this means very expensive property damage or possibly even death.
The CNRA along with the NRA in the US has made it a rule (unless flying in the White sands desert area with security clearance) that no rocket shall be constructed of metal. I'm taking a guess that this is to prevent worse damage?
True at the speeds we're talking about, whether plastic, carbon fiber, metal or cardboard, a rocket coming in ballistic from high up is going to be capable of doing incredible damage.

I hope this clears things up.
High powered rocketry is a whole other ball game.

 

[Flaminpyro]

You are correct it was a ESTES kit from way back and it did tumble back to earth, I think it was an "A" motor ? the fins were made from pop sickle stick or tong depressors I can't remember now :thinking:

Yea this new BIG yellow one was pretty cool to watch and it did come down on a para chute.

BTW a lot of the bigger rockets were made with lots of aluminum in the frame and body, some were made with aluminum and fiberglass sections, many had fiberglass and carbon fiber nose cones and frame members.

This was pretty funny and I wish I had a video of this, about 10 min before the blue rocket buried it's self 12 feet away from me, I was walking back towards my trailer and another rocket came in a
bit slower and I seen this one coming down so I stopped to watch (it was wider and longer a little bit and black in color) and about 400 feet away it buried it's self about 1.5 feet in the ground so
there was about 3.5 to 4 feet sticking out of the ground, I stood there watching thinking how cool was that when the para chute ejecting charge went off and blew the back half of the rocket up
in the air, what a sight, wish I had my camera for that one :tinfoil:

Well here's more cool rocket pictures from that event, I do have some video of rockets leaving the launch pads.








Oops how'd that get in here

Jeff, that last pic of the yellow rocket brings back old memories; I used to have one of those in the original 8" size back in the day.
I'm pretty sure that the one I had was an "Estes" kit. If I remember correctly, wasn't that the one that came back down without the need for a parachute?

Edit: I just checked the Estes site, and they still have a similar rocket to this day, they say it "tumbles" back to earth.

 

[BowtieGuy]

Oops how'd that get in here

I hope everyone notices the pertinent safety instructions written on the side of this "small" firework!

BTW, Great rocket and firework pics. Jeff.

 

[Benm]

likewise, a rocket falling from 6000m will be travelling the same speed as a .22LR. (sonic) ~1234.54Km/hr.

That seems to be a very high number, i wonder on what resistance profiles and density this is based.

After all, normally all the fuel would be spent so the rocket would weigh much less falling down compared to flying up.

This would essentially mean that i when i would throw out the rocket shell from an airliner, it would impact the ground at supersonic speeds. I find this quite amazing - i'm no rocket, but the terminal velocity of a human falling is about 300 km/h when vertical, and about 200 km/h when 'attempting to fly' in a horizontal position.

I doubt an empty rocket would be that much more dense or aerodynamic to achieve about 4 times that number, though i could be wrong there.

As far as danger goes it doubt it matters much if you are struck directly. A 2 meter aluminium pipe hitting you on the head at mach 1 would probably kill you, but so would a 2 meter length of balsa wood really.

 

[Seoul_lasers]

That seems to be a very high number, i wonder on what resistance profiles and density this is based.

After all, normally all the fuel would be spent so the rocket would weigh much less falling down compared to flying up.

This would essentially mean that i when i would throw out the rocket shell from an airliner, it would impact the ground at supersonic speeds. I find this quite amazing - i'm no rocket, but the terminal velocity of a human falling is about 300 km/h when vertical, and about 200 km/h when 'attempting to fly' in a horizontal position.

I doubt an empty rocket would be that much more dense or aerodynamic to achieve about 4 times that number, though i could be wrong there.

As far as danger goes it doubt it matters much if you are struck directly. A 2 meter aluminium pipe hitting you on the head at mach 1 would probably kill you, but so would a 2 meter length of balsa wood really.

Just to further the explanation, while you are right about the human falling bit, and in this situation you've got a great deal of drag happening. In an aerodynamic projectile such as a rocket, very little of this applies, while the real speed will be different from the calculated terminal velocity, it is safe to assume that a rocket falling from +2Km will be coming in at least +600Km/hr. Yes the rocket will change mass once the fuel has been burned up. It changes the mass by ~400g. Assuming the Rocket still weighs over 1.5Kg coming down from just a hair over 2Km without a parachute. You can use the formula below.

Edit: the calculator assumed 0 drag.... assuming a drag of 0.45 in the best case scenario something in the neighbourhood of 80 m/s is more realistic from 2Km?

The formula is v = the square root of ((2*m*g)/(ρ*A*C)).

 

[Benm]

That would still depend on Cd though, which would be equivalent for launching and falling IF the rocket somehow kept a nose-down attitude during the fall. Also A would be considerably larger if it was falling sideways.

If you launched it at a moderate angle it would probably keep it's nose-first attitude (like an artillery shell does), but if you shoot it straight up i doubt it would make a nice parabola and come down nose first in most cases. It could just as easily start coming down ass-first and spin out of control from there.

 

[Rivem]

That seems to be a very high number, i wonder on what resistance profiles and density this is based.

After all, normally all the fuel would be spent so the rocket would weigh much less falling down compared to flying up.

This would essentially mean that i when i would throw out the rocket shell from an airliner, it would impact the ground at supersonic speeds. I find this quite amazing - i'm no rocket, but the terminal velocity of a human falling is about 300 km/h when vertical, and about 200 km/h when 'attempting to fly' in a horizontal position.

I doubt an empty rocket would be that much more dense or aerodynamic to achieve about 4 times that number, though i could be wrong there.

As far as danger goes it doubt it matters much if you are struck directly. A 2 meter aluminium pipe hitting you on the head at mach 1 would probably kill you, but so would a 2 meter length of balsa wood really.

I've got to agree on the terminal velocity being much lower than sonic. Bullets have been measured around 100 m/s at terminal velocity during studies on their lethality if shot directly up. I'd assume the drag coefficient of a bullet is probably much lower than a rocket's, and the density should be much higher.

Cool rockets nonetheless.

Edit: This kills me as an engineer:

According to the math the rocket will have an impact velocity of (theoretically) 712.76 km/h. This is because there will be little to no air resistance/drag on the airframe body.
likewise, a rocket falling from 6000m will be travelling the same speed as a .22LR. (sonic) ~1234.54Km/hr.

This can't be assumed unless you're talking about something that has little to no geometry. Rockets have more wake than some streamlined cars and many common aircraft. The common drag coefficients are usually cited around 0.6 to 0.75. Bullets are around 0.3.

 

[Seoul_lasers]

I've got to agree on the terminal velocity being much lower than sonic. Bullets have been measured around 100 m/s at terminal velocity during studies on their lethality if shot directly up. I'd assume the drag coefficient of a bullet is probably much lower than a rocket's, and the density should be much higher.

Cool rockets nonetheless.

Edit: This kills me as an engineer:


This can't be assumed unless you're talking about something that has little to no geometry. Rockets have more wake than some streamlined cars and many common aircraft. The common drag coefficients are usually cited around 0.6 to 0.75. Bullets are around 0.3.

right... the formula that was used didn't take the drag coefficient into account at all. True. :thinking:
I used a Java Calculator that assumed a 0 drag coefficient even after changing the drag. huh.

Face palm.. feel stupid.

Thanks for clearing this up.

 

[Seoul_lasers]

Looks like we have a new launch window in about 2 weeks time. 2nd week of Feb.

The local Fire department is all for it. The chief's son is sending up a fiberglass kit on a our first ever reloadable engine.

I fully expect a supersonic flight for this next launch to just over 3Km altitude at apogee. We must launch with our larger tripod.

 

[Benm]

Make sure to clock the top speed on the way down as well if you can

 

[Hemlock_Mike]

That small Estes rocket was called a "Streak".
1/2 A to an A engine recommended. My friend got
tired of it and launched with a C6-7 ---- We found
it three days later beside a gravel road 4 miles away!
HM

 

[Seoul_lasers]

Make sure to clock the top speed on the way down as well if you can

hmm... That'll be interesting. I sure hope it won't come in ballistic. It will have an altimeter on it and a
time delay bursting charge to fire the main parachute.

I REALLY don't want the fiberglass rocket sticking out of a roof of a house or a car.
This rocket has a metal nosecone and is nice and sharp.

Rocket assisted lawn dart.

 

[Benm]

Er yeah, that sounds pretty bad if it were to strike someone on the ground.

I'm not sure where the center of gravity of the rocket will be after the fuel as been spent, but having a fiberglass body with a metal nosecone could probably favour a nose-down return trajectory... please don't launch these things anywhere near me

 

[Seoul_lasers]

Yesterday we had a mostly clear ceiling so I decided to test a modified Astro arrow. This is a high density cardboard rocket with HDPE fines. The cardboard was soaked in cyanoacrylate (plasticized) and sanded smooth. This rocket was intended for up to a G series engine. I had a slightly larger engine tube from one of the other builds and decided to send this rocket up on a slightly larger engine. :evil: Well, we achieved supersonic flight. Rocket's altitude was tracked to 7945.3ft (nearly 3Km) with a maximum velocity of 1845.2Km/hr some 0.82 secs after launch.

Enjoy the video clip, this rocket really moves. Turn the sound down.

You'll notice the ending frame has a bit of side distortion. This is because the camera had to use a very high frame rate burst to capture the flight properly.
Notice the debris on the bottom of the launcher.

The rocket was tracked both by ground and by onboard altimeter.

This all blue rocket is our first complete fiberglass rocket kit. It is slightly heavier than the other rocket kits we've put together but
it requires a reloadable 29mm engine. They very capable of supersonic flight (+ 2000Km/hr) and as such I think this one will be fired at a larger field.
This one will get a RF tracking beacon and altimeter. It's quite expensive!!

Notice the 1" dia fiberglass cone with the MgAl alloy tip.