I've used Marvel Mystery Oil to loosen up & clean bearings. Not sure if it would react with the rubber or not.
<f i r e b a l l [space] x l 5 [search]>
Ooh, heck yeah! With or without a sled, that's a nice design. Do I surmise correctly that it was sled launched in the show?
<f i r e b a l l [space] x l 5 [search]>
Ooh, heck yeah! With or without a sled, that's a nice design. Do I surmise correctly that it was sled launched in the show?
I would be concerned that the 2 lb sled, once free of the rail, could continue upward and then fall back to earth and land on the launch rail, or you, causing unwanted damage.
One option would be to keep the cart on the track. Place a close-off plate at the end of the track with rubber bumpers.
... For cart recovery, what about a smallish chute attached to a longish (note technical terms here) thin bungee cord? The bungee would absorb some of the shock of opening the chute but hopefully it would go high enough to hit the ground under the chute. Having the last bit of track at say 10 degrees off vertical would give the cart some horizontal velocity that would at least help keep the chute full.
Okay, let’s get out of the box, go with something easier and low mass and low resistance.
Ditch the track.
Have pivot assembly, two rods and a rocket “basket”. Moment arm is, say, 4 feet. central pivot point is about 5-6 feet above ground surface.
Start with basket on far right, rods horizontal, rocket aimed Down (unless in Australia.).
Simultaneous cluster ignition of sled motors and long delay, preferably long burn, rocket motor.
Burn strings (actually rubber bands would work admirably) hold the basket in place, BASKET DOES NOT MOVE UNTIL BOTH THE SLED AND ROCKET MOTORS ARE LIT.
Upon burn string release, gravity, sled motor, and rocket motor forces swing the rocket down to horizontal (use gravity to overcome inertia and initial “starting” friction.).
Once horizontal, the motors and kinetic energy will continue the swing until the rocket is vertical on the far left.
The moment bars hit a “stop” at the left 90 degree vertical point. (The basket could be pretty light, most of the mass would be the motor mount and motor casing, and maybe a very short “tower” holding the rocket in appropriate orientation.). Rocket keeps moving straight up based on its still firing motor and the kinetic energy it got during its half circle basket track.
What could go wrong?
Ye ole pit and the pendulum scenario! Very nice!
A couple of thoughts...
Not sure a sled would be that different, in either case you need to get rocket up to what, 50 feet per second bay the end of the rod/ track/ pendulum
- Everything would happen so quickly it would be a blur....
For a taut rubber band just about instantaneous. It’s what I use for my helicopters and airbrake recovery rockets
- What's the burn rate of a rocket motor through a string or a rubber band?
What’s the philosophy of your current project? Multiple different perspectives. For me, it is some sort of ground pathway where kinetic energy is imparted to the vehicle either in lieu of or in addition to the onboard rocket motor.
- Why do you even need a sled motor?
The peak thrust for a D12, 1/4 second after ignition, is just under 30 N. So two of them push a 1 kg sled at 60 m/s², or about 6 gees.
The average thrust is only just over 10 N, so that would give about 2 gees.
Both of those are horizontal, no friction. Subtract 1 gee if going vertical. It's enough for a starting WAG, if you can WAG the wheel friction.
I have inserted the answers into your quote
Okay, let’s get out of the box, go with something easier and low mass and low resistance.
Ditch the track.
Have pivot assembly, two rods and a rocket “basket”. Moment arm is, say, 4 feet. central pivot point is about 5-6 feet above ground surface.
Start with basket on far right, rods horizontal, rocket aimed Down (unless in Australia.).
Simultaneous cluster ignition of sled motors and long delay, preferably long burn, rocket motor.
Burn strings (actually rubber bands would work admirably) hold the basket in place, BASKET DOES NOT MOVE UNTIL BOTH THE SLED AND ROCKET MOTORS ARE LIT.
Upon burn string release, gravity, sled motor, and rocket motor forces swing the rocket down to horizontal (use gravity to overcome inertia and initial “starting” friction.).
Once horizontal, the motors and kinetic energy will continue the swing until the rocket is vertical on the far left.
The moment bars hit a “stop” at the left 90 degree vertical point. (The basket could be pretty light, most of the mass would be the motor mount and motor casing, and maybe a very short “tower” holding the rocket in appropriate orientation.). Rocket keeps moving straight up based on its still firing motor and the kinetic energy it got during its half circle basket track.
What could go wrong?
I am not so sure about that. If I understand my physics right, if you swing a ball on a rope, and suddenly release the rope, the ball will continue on a straight trajectory on the exact heading it was on when you released it.One problem is that you impart angular momentum to the rocket. It will continue to rotate until the angular momentum is gone.
One problem is that you impart angular momentum to the rocket. It will continue to rotate until the angular momentum is gone.
I am not so sure about that. If I understand my physics right, if you swing a ball on a rope, and suddenly release the rope, the ball will continue on a straight trajectory on the exact heading it was on when you released it.
Where is @prfesser when you need him?
Hi, Great concept.
I have a question you might have already addressed elsewhere, but how does the Estes rocket dragster car not require the same launch "rod" specs as a vertical flying rocket? I see they use a piece of string or something to guide it down the track. A modified car and track with the final launch over 30 degrees for the flying rocket section. Would that be ok/legal in the rocketry world?
All the best.
Just this morning I found this, that I missed earlier. I haven’t looked in NFPA 1122 to see if something similar exists for model rocket motors? Im sorry I didn’t find it before. I added the underlining.:
4.17.1 No person shall ignite and launch a high power rocket horizontally, at a target, or so that the rocket's flight path during ascent phase is intended to go into clouds, directly over the heads of spectators, or beyond the boundaries of the launch site, or so that the rocket's recovery is likely to occur in spectator areas or outside the boundaries of the launch site.
Assuming the basket maintains the orientation of the rocket perpendicular to the radius of the curve, the CENTER OF MASS of the rocket will keep going straight. You are correct that the rocket has a non-neglible length, therefore the tip of the nose at moment of release is NOT going exactly the same direction as the CG and even more catywampus relative to the tip of the tail. But I THINK by definition these forces are balanced at the CG, so I wouldn't anticipate any pitch or yaw forces.For the direction of motion of the center of gravity, that's correct. But the ball will retain the angular momentum it gains before it is released. If you look carefully, you'll see that the ball is spinning as it travels on it's straight path. For a ball that doesn't matter. If the rocket leaves the launch trapeze spinning on an axis parallel to that of the trapeze, it matters a whole heck of a lot.
The regular NON High Power Code specifically prohibits targeting and launch angles over 30 degrees from vertical.Well, the rule Steve referred to (see below) was for High Power Rocketry.... and my sled will not be High Power, and neither were the Estes Dragsters.
It also doesn't say it can't be launched horizontally (and then a period). There is a comma and then it goes on to state specific cases.
The regular NON High Power Code specifically prohibits targeting and launch angles over 30 degrees from vertical.
Something I thought was a very mild faux pas at NSL 2019 (otherwise a spectacularly well run operation) last year was a competition to see who could land a rocket closest to a cone placed maybe 50 or 100 feet from the low power pads, measured tangential or even slightly away from flight line. Technically I would think anything other than "closest to the pad" would be called targeting.
https://www.nar.org/safety-information/model-rocket-safety-code/
The regular NON High Power Code specifically prohibits targeting and launch angles over 30 degrees from vertical.
https://www.nar.org/safety-information/model-rocket-safety-code/
My interpretation is that “launching at a target” would be to aim your flight in the direction of a target with the intent of striking the target at speed.
Attempting to land a rocket safely at a specific spot wouldn’t count as that, again in my interpretation.
Logical. I think however this became a potential concern with active recovery devices (of which the only routine and accepted version is RCBG). If you intend to land your rocket somewhere OTHER than its point of origin, could that ability lend itself to nefarious uses. An example was using active recovery and GPS guidance. Slippery slope.....
Addendum
Code does cover this however as it DOES say your rocket as launched should be intended to land within confines of launch field
My rocket is attached to a sled "to ensure that the rocket flies" within 30 degrees of vertical.
Using your logic you couldn't bench test a rocket horizontally. When does a rocket launch? I would say when the motor is ignited AND the rocket is no longer constrained.
Rocket leaves the trapeze at 50 fps. One full rotation of the trapeze would be 8π ≈ 25 ft. At release the rocket will be tumbling at about 50 fps ÷ 25 ft/rev = 2 rev/sec (or 120 rpm). That's not a rocket, it's a firework. (Use a sparky motor and don't release the rocket at all, and it's a pretty cool firework.)Okay, let’s get out of the box, go with something easier and low mass and low resistance.
Ditch the track.
Have pivot assembly, two rods and a rocket “basket”. Moment arm is, say, 4 feet.
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