Flying AeroTech M2400 with only 2 grains? (It normally has 3)

[cwbullet]

The OP gave up on the plan to fly the motor in a 2-grain config back in post 11.

Yup. It seems folks are beating a dead horse.

 

[Handeman]

Yup. It seems folks are beating a dead horse.

True, except now they intend to add weight to get a M motor to fly only as high as a 2/3 as big L motor. That's a lot of weight.
This is a decision the typical university team makes because they don't have the experience or systems engineering know how to understand that a change like that affects many other parts of the rocket. This is probably a project they need to finish this semester so they make unsafe decision because they can't wait for a new motor and still hit their schedule to complete the project by the end of the school year. These situations are all too common with the SLI, IREC, SAC, etc. teams and is one of the reasons so many of their flights fail. I'm actually surprised when their flights go as expected.

 

[cwbullet]

True, except now they intend to add weight to get a M motor to fly only as high as a 2/3 as big L motor. That's a lot of weight.
This is a decision the typical university team makes because they don't have the experience or systems engineering know how to understand that a change like that affects many other parts of the rocket. This is probably a project they need to finish this semester so they make unsafe decision because they can't wait for a new motor and still hit their schedule to complete the project by the end of the school year. These situations are all too common with the SLI, IREC, SAC, etc. teams and is one of the reasons so many of their flights fail. I'm actually surprised when their flights go as expected.

They decided not to do it, so why is this not continuing to beat the dead horse? We all decided it was a bad idea.

 

[mikec]

Agreed that adding weight is also not a good idea, I think we all acknowledge the problems with student teams, but I suspect the OP has long ago moved on. Rinse and repeat across many student threads.

The only thing I'm optimistic about is that for every one of these frustrating ask-for-advice-then-ignore-it threads, I'm sure there are 10 student teams who listen to their mentors. At least that's been my experience.

 

[AeroTech]

Nice anecdote, glad to hear it!
How does it help this flyer make a sound and safe decision?

It was not necessarily intended for the flyer. It was general comment and observation directed to the readers of this thread. If someone wanted to take it literally as advice (which it wasn't) then the person desiring to do this would need to static test several samples of the motor in question and evaluate the data before ever considering flying it in the modified configuration.

 

[Reinhard]

Agreed that adding weight is also not a good idea, I think we all acknowledge the problems with student teams, but I suspect the OP has long ago moved on. Rinse and repeat across many student threads.

The only thing I'm optimistic about is that for every one of these frustrating ask-for-advice-then-ignore-it threads, I'm sure there are 10 student teams who listen to their mentors. At least that's been my experience.

If this is the team that I think it is, then they *are* listening to the advice of their mentor, by having this test flight before SAC. Simply having their maiden flight at SAC would require less effort. Some teams do so, often by necessity because of limited launch opportunities (esp. international ones).

Also, regarding the advice of flying a smaller motor, please understand that this a German team flying in Germany. HPR motors are available in Europe, but not so much on a short notice. This is especially true for 75mm+ motors and even more so when only a fraction of propellants is suitable (high thrust ones in this case).

That being said, I think it's worthwhile to see if they can get the proper nozzle in time and turn the motor into a research L1520T (unless @AeroTech advises against that).

Reinhard

 

[nikobark]

If this is the team that I think it is, then they *are* listening to the advice of their mentor, by having this test flight before SAC. Simply having their maiden flight at SAC would require less effort. Some teams do so, often by necessity because of limited launch opportunities (esp. international ones).

Also, regarding the advise of flying a smaller motor, please understand that this a German team flying in Germany. HPR motors are available in Europe, but not so much on a short notice. This is especially true for 75mm+ motors and even more so when only a fraction of propellants is suitable (high thrust ones in this case).

That being said, I think it's worthwhile to see if they can get the proper nozzle in time and turn the motor into a research L1520T (unless @AeroTech advises against that).

Reinhard

We've got an M1560, so everything is fine now

 

[sharkbait]

We've got an M1560, so everything is fine now

That’s good to hear

For future reference
RCS is quite transparent with their propellent grains and gives the a & n and other info for each type of propellent they sell, you could use the same nozzle that came with the reload and open up the cores of the two grains accordingly to achieve a proper kn for the modified load

Disclaimer: I am not recommending this for you guys and glad you were able to get a different motor, but just pointing out that there are different ways to skin cats, good luck with your flight