2020 TARC challenge, is there anything that says you CAN’T use an 800 foot cord

[BABAR]

https://rocketcontest.org/wp-conten...les-TARC-2020-Final-as-of-18-May-2019.doc.pdf

Not that I can see anyone doing it, but is there anything in the rules that would DISQUALIFY a team from attaching an 800 foot cord to 50 gram stake stuck in the ground on one end and a 550 gram rocket on the other? Only argument I can see is they might consider if it is tethered to the ground the earth is part of the rocket, which would likely exceed the 650 gram limit.

Another option would be attaching a 750 foot cord to a parachute that just sits next to the pad, doesn’t weigh much, and definitely will slow the rocket at 750 feet. Might be less stress on the egg than Kevlar attached to the ground.

Definitely meet the requirement that all parts of the rocket stay tethered, likely will keep the rocket from drifting out of sight, and make recovery easier!

 

[kuririn]

Heh, sounds like Kirk's "Kobayashi Maru" solution.


Gotta love a creative thinker!

 

[BABAR]

I believe the additional quote is,

“It had the advantage of having never been tried.”

https://getyarn.io/yarn-clip/084ead2d-b084-471d-8b8b-00a0df4db334

 

[blackjack2564]

Maybe not that long but I have done 100 ft trailing behind.

It causes the rocket to "rainbow arc " severely ,due to the drag.
The first 10ft or so must be kevlar or flame will burn the cord. Along with that a serious increase in motor size [impulse] is required due to added considerable weight. My guess is 1-2lbs, if you add 750ft of cordage.
Not doable due to safety constraints in my opinion

 

[DAllen]

Not doable due to safety constraints in my opinion

Completely agree however, I sure wouldn't mind watching someone try it though lol. Recovering all that cord would be a giant PITA.

 

[rocketdoctor99]

I think the cord would be counted part of the rocket and exceed the 650 gram weight limit. It would piss off alot of contestants if you could get away with it

 

[boatgeek]

I seriously considered it but couldn't think of a way to make it practical. If you can get it to work, you'll have a rule with your name on it for the next year!

 

[BEC]

If you can get it to work, you'll have a rule with your name on it for the next year!

That's for sure!!

As one who does official observer duty for lots of local TARC flights, I would have to see what the flight looked like as of course it has to be a per-the-safety-code safe flight. Also, I would certainly include the weight of the kevlar in the weight I'd have to verify before signing off on the score....

Also, remember the altitude is only one part of the score.

 

[boatgeek]

Also, remember the altitude is only one part of the score.

I think this is the way to keep the loophole closed, for this year anyway. I believe that the time is from when the first part of the rocket hits the ground. The tether would be part of the rocket (all recovered in one piece), so the moment a piece of it hit the ground, time stops. You’d either have to feel it up really fast or take a 6-10 second flight.

For years when you time the egg capsule and not the fin can, it might be more feasible.

 

[BEC]

I think this is the way to keep the loophole closed, for this year anyway. I believe that the time is from when the first part of the rocket hits the ground. The tether would be part of the rocket (all recovered in one piece), so the moment a piece of it hit the ground, time stops. You’d either have to feel it up really fast or take a 6-10 second flight.

For years when you time the egg capsule and not the fin can, it might be more feasible.

Yes, this year it's all supposed to come down together, so time stops as soon as part of it touches the ground. Here's the first sentence from the duration scoring section of this year's rules: "The duration score for each flight shall be based on total flight duration of the rocket, measured from first motion at liftoff from the launch pad until the moment that the first part of the rocket touches the ground (or a tree) or until it can no longer be seen due to distance or to an obstacle."

 

[Sooner Boomer]

Ha! I can be within the rules and beat them, too!

"The duration score for each flight shall be based on total flight duration of the rocket, measured from first motion at liftoff from the launch pad until the moment that the first part of the rocket touches the ground (or a tree) or until it can no longer be seen due to distance or to an obstacle."

"First motion at liftoff" starts the timer. Doesn't say "motor ignition", says "motion". Have a doohickey, so that when ignition voltage from controller turns on, it makes the rocket jump, then delays motor ignition for however long you want to wait.

 

[blackjack2564]

There was a name for dragging long cord behind a rocket...drove me nut yesterday trying to think of it......well sheeeeebang!

Any other old-timers remember doing this way back.... "St Louis Arch"!

 

[MClark]

If the cord is part of the rocket and one end never leaves the ground the altitude would be zero.

M

 

[boatgeek]

If the cord is part of the rocket and one end never leaves the ground the altitude would be zero.

M

Per the rules, the altitude score is based on what the altimeter records. If the altimeter goes to 800 feet, then that's the altitude score.

Now imagine a boosted dart with a very long shock cord between the booster and the dart. The egg could be in the booster and have a very large parachute. The dart would hold the altimeter. You could probably figure out a way to communicate between the two via wifi so that the booster grabs the shock cord hard to stop the dart when it reaches the correct altitude. Then there'd be some trickery to get one part of the rocket to hit the ground at just the right moment for zero time score.

This is probably a lot harder than just building a rocket and tuning it. Or having more normal onboard controls.

 

[kuririn]

If you can get it to work, you'll have a rule with your name on it for the next year!

The Babar paradox
The Babar manuever
The Babar gambit
The...

 

[jlabrasca]

The Babar paradox
The Babar manuever
The Babar gambit
The...

More likely to be named after Raymond Sinclair, or Sidney Stratton, or whoever invented General Technics monomolecular wire, or maybe some unpronounceable tnuctip name (did the tnuctipun have personal names?). Recovery would be tricky, too. Pick up the tether, then ask someone to pick up your fingers...

 

[Oscar G.]

I like "The Babar ground assisted altitude control manuver"

The other thing I love, is that "anybody have altitudes for estes alpha" is the first thread I ever posted.
who would have known it would prompt the next generation of altitude control and revovery . . .

 

[Nytrunner]

Which part of the rocket is the cord attached to? 800 ft of line pulling on anything other than the central axis of the rocket will cause it to....adjust course

 

[Zeus-cat]

If I was the timer I would hit start and stop as fast as possible after motion. The rocket tether is touching the ground so your time is essentially zero.

 

[Sooner Boomer]

Pick up the tether, then ask someone to pick up your fingers...

That's why they make gloves from the stuff; to handle the monomolecular wire.

 

[BABAR]

If the cord is part of the rocket and one end never leaves the ground the altitude would be zero.

M

Not true

By the rules, the onboard altimeter is the SOLE determinant of altitude.

 

[BABAR]

If I was the timer I would hit start and stop as fast as possible after motion. The rocket tether is touching the ground so your time is essentially zero.

True but easily evaded. Don’t attach the cord to the GROUND

Timer starts when rocket starts to move. Timer stops when first part of rocket touches GROUND or TREE. Rules are very specific on this point. Doesn’t say anything about the PAD.

attach the cord by a clip to the PAD. So your cord and clip starting point never touches the ground. If you count the pad as part of the ground, EVERY rocket has a time of zero as EVERY rocket starts moving but is in contact with the pad (on the rail) for a finite time after first motion. NO rocket instantaneously departs the pad. Plus there is NOTHING in the rules that says all parts of the rocket MUST leave the pad simultaneously. Only that time starts at first motion and stops when a part of the rocket touches GROUND or TREE.

Where you DO run into a problem is that the CORD is definitely part of the rocket, for both weight purposes and for contacting ground as rocket descends. Even an attached cord to the pad will have a length contact ground well before the rocket lands..........Unless..........

Last 200 feet of cord is doubled with 100 feet elastic, end attached by clip to the pad. Tiny streamer on the clip. When rocket hits 780 feet, that’s end of Kevlar, the jerk pulls the clip off the pad AND separates the altimeter. This also prevents your Zero score, as EVERY part of the rocket DOES depart the pad.

Goal 1 met, altitude target.

Elastic retracts the cord upward, plus the cord is attached to the payload section which is still going up.

Now you have to hope the higher altitude of the payload section AND the elastic retraction AND THE STREAMER can keep the clip and string airborne longer than the 33 seconds you need for the motor end of the rocket to come down to earth.

 

[Nytrunner]

This isn't rocket science, this is loophole lawyering.

 

[BABAR]

That's why they make gloves from the stuff; to handle the monomolecular wire.

SOMEBODY read Larry Niven’s Ringworld

 

[BABAR]

This isn't rocket science, this is loophole lawyering.

I prefer to consider it “Thinking outside the Jury Box.”

Also, why is a mechanical solution to meeting given parameters considered suboptimal to a standard solution trying to pick right motor and delay and electronics and chute size?

 

[Sooner Boomer]

That which is not specifically prohibited, is allowed.

 

[jlabrasca]

That which is not specifically prohibited, is allowed.

Everything not forbidden is compulsory.

 

[anbhtblr]

Everything not forbidden is compulsory.

What a deep rabbit hole!

 

[cerving]

You may have a job as a NASCAR race engineer...

 

[jadebox]

Weaseling around the rules can work in both directions.

The length of the rope might be considered part of the rocket in its undeployed state making the rocket too long.