That is great! It looks like you had fun.
Well, it looks like life has conspired to make true qualifying flights impossible. There simply will be no opportunity for the team before the deadline.
However, it's not that bad, considering that making the nationals wasn't a serious goal. Based on what we learned from the practice flights, there would be almost no way of getting a good score anyway; can't make the altitude.
Instead, the girls will come to a Rad Rocks launch with me one day in the spring or summer, and do their flights as if trying to qualify, and we'll calculate their score. I'll give them some LPR rockets to fly as well if they want. So at that point they will have completed the year's journey, maybe not quite what was originally hoped for but definitely better than it could have gone. I think they're coming out of this with a positive feeling. No clue yet if they're going to try to get a team together for next year, can't worry about that yet.
Thanks for all the advice and help along the way. I'll report back here with the results of the "qualifying flights" whenever they happen.
Hi everyone, I'm not sure if this thread is still active but I'm leading a TARC team for the first time this year and I had a few questions.
1. We are using OpenRocket to model the rocket and everything looks fine but the flight time looks a little unrealistic. We are using two body tubes and the weight of the rocket is around 300g right now. According to the software, it goes up to around 280m but has a flight time of around 40 seconds with only one 30 cm diameter parachute. The parachutes are set to come out at apogee and there is a shock cord attaching the two parts body tubes together. Is there something we have to specify to make sure that it thinks both parts are coming down together with the one parachute or what are we doing wrong?
2. We are also trying to find a good E- class rocket motor that's reliable and easy to find with an impulse of around 33. We can adjust the design to make sure that it fits a rocket motor that won't be difficult to find or use. Any recommendations?
What motor are you currently using in open rocket to achieve that altitude?
You can also double check your specs utilizing the ThrustCurve app or website for a sanity check on altitudes:
https://www.thrustcurve.org/
It is now!Hi everyone, I'm not sure if this thread is still active
Can you post the file?1. We are using OpenRocket to model the rocket and everything looks fine but the flight time looks a little unrealistic. We are using two body tubes and the weight of the rocket is around 300g right now. According to the software, it goes up to around 280m but has a flight time of around 40 seconds with only one 30 cm diameter parachute. The parachutes are set to come out at apogee and there is a shock cord attaching the two parts body tubes together. Is there something we have to specify to make sure that it thinks both parts are coming down together with the one parachute or what are we doing wrong?
We are using an E11J motor right now but the optimum delay is 5 seconds even though every motor I found online comes with a 3 second delay. The E20 also works but its a single use motor and we want to use a reloadable one.What motor are you currently using in open rocket to achieve that altitude?
You can also double check your specs utilizing the ThrustCurve app or website for a sanity check on altitudes:
https://www.thrustcurve.org/
sadly, our sponsor has told us not to post our design online.Can you post the file?
We are using an E11J motor right now but the optimum delay is 5 seconds even though every motor I found online comes with a 3 second delay. The E20 also works but its a single use motor and we want to use a reloadable one.
sadly, our sponsor has told us not to post our design online.
Thanks everyone so much for the quick responses.
We are using an E11J motor right now but the optimum delay is 5 seconds even though every motor I found online comes with a 3 second delay. The E20 also works but its a single use motor and we want to use a reloadable one.
sadly, our sponsor has told us not to post our design online.
Yes, thanks for the advice but we did change it to an Aerotech E20-7 engine. The TARC rockets this year are actually much lighter than previous years because instead of carrying 2 or three eggs, we only have to carry one egg for the payload which cuts the mass down by about 15% - 20%. According to openRocket, the apogee will be 295m which is way more than 243m we're aiming for in qualifications(it's overpowered on purpose like you suggested until we can see how it really flies at our first launch).An E11 seems pretty small for a TARC rocket. To be fair, I have not looked at the requirements for this year. The TARC teams I have seen use F motors.
Usually it is better to slightly overpower the rocket; especially based on sim data. Sims are notorious for overestimating altitude. Better to have more power and then add weight or drag to lower the altitude. It is easier to reduce altitude than to add it.
A 30cm (12") parachute seems a little small to me. You might try 15"-18" and see how that looks. You can always reef the shrouds a little to bring it down faster if you need to. You are definitely on the light and low impulse side of TARC designs. Do you have a built rocket yet to confirm that this is a real weight? Everyone (and especially students) tend to build heavy until they have lots of experience.
Aerotech's master order list (here) only shows a 3-second delay for the E11, so there's probably no 5-second delay available. On the plus side, the 24/40 case has lots and lots of options for you. You might look at the E18 or E28 instead--they both have 4s and 7s delays available in similar total impulse and weight motors. Higher thrust off the pad also tends to make the rocket weathercock less in winds, making flights more predictable.
First, I want to clarify that using we are now using an E20-7 motor with a 15 inch parachute. The liftoff weight is about 330 grams. Total flight time, from launch to touchdown, is 46 seconds with the delay set to 7 seconds.There are a lot of "problems" here :
(1 ) The use of a 30 cm (11.81") chute, in a 300 gram (10.58 oz.), descending from 280 meters ( 918 ft.) will have a Descent Rate of 9.28 meters/sec. (30.45 ft/sec.)
(2) The "Optimal Delay" is the "800 lb. Gorilla in the room" . . .
(3) Without having any idea of the design, "guesswork" is a bad thing, especially when "precision" is called for.
***************************************************************************************************************************
Where are you located and who is your Sponsor ( did you mean "Mentor" ) ?
Without any physical data to work from, you will only get a bunch of "WAG's" ( Wild Azz Guesses ).
***************************************************************************************************************************
The next part is directed at your Sponsor . . . ( Not you, or the Team, at all )
This may sound a little "snarky" ( not intended ) but, if your Sponsor has such a "Whiz-Bang" design
that is must be kept "top secret", why isn't he satisfactorily answering the questions being asked here ?
***************************************************************************************************************************
Back to the Team, now . . .
I and, I am sure, many others would love to help you out, but more information is needed.
Ask your Sponsor to post here !
Dave F.
An E18 motor is would also be good for our design but our team has decided that single use motors would be more beneficial since they save time and we usually have a short amount of time to launch every few weekends.[
An E 11 is under powered. There are other more powerful e reload motors that would be a better option. When you are lofting a payload such as an egg you really need a motor with a quicker thrust at ignition and the E 11 would not do that. Something more like an E18W-4,8 which is on the TARC list of apporved motors for 2020: https://rocketcontest.org/wp-content/uploads/2019/10/Rocket-Motors-Approved-for-TARC-2020.pdf
Estes BP motors are probably not your best option for TARC, but if you want to use them, it's no problem... just wrap masking tape several times around the last 1/4" of the motor, enough to create a thrust ring. Use a knife to cut off all the excess tape hanging off the end. Works fine, and that's what pretty much everyone does. Works perfectly with retainers designed for composite motors, no hooks required.Quick question tho for everyone: since we'll probably experiment with different motors after we're done building the rocket, is there a way to build a bottom section that can accommodate both aerotech motors which require an engine retainer and estes motors which require a back stop and a clip to hold them in?
Estes BP motors are probably not your best option for TARC, but if you want to use them, it's no problem... just wrap masking tape several times around the last 1/4" of the motor, enough to create a thrust ring. Use a knife to cut off all the excess tape hanging off the end. Works fine, and that's what pretty much everyone does. Works perfectly with retainers designed for composite motors, no hooks required.
Poke a small vent hole or two (or three) in the body tube opposite to where the eggs are removed. This will eliminate pulling against a vacuum and should make it easier to remove them.1) Last year, we had trouble getting the eggs out of the tube after the flight to check if they were cracked.
Should we attach the parachute to the bottom part of the rocket, top part, or to the shock cord itslef?
Poke a small vent hole or two (or three) in the body tube opposite to where the eggs are removed. This will eliminate pulling against a vacuum and should make it easier to remove them.
Thanks for the responses guys. I have a few more questions:
1) Last year, we had trouble getting the eggs out of the tube after the flight to check if they were cracked. This was because the foam protectors fit very tightly inside the tubes to protect the eggs. In the end, we just put a blukhead under the eggs and tied some rope on it that went to the top of the body tube so that we could pull up of the cord pushing out all the eggs. It didn't really work because half the time, the bulkhead would slide up onto one side tube or we would crack the egg on the bottom. Is there another way we can take easily take out the eggs?
2) Also, TARC requires both parts of the rockets this year to come down together meaning we have to use a shock cord. Should we attach the parachute to the bottom part of the rocket, top part, or to the shock cord itslef?
Enter your email address to join: