Review & Advise on L1 attempt Flight Profile, please

The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.
Yes. There are a LOT of things that are supposed to be asked of an L1 that seldom are. I contend that if the certifying officials were following the checklist we would have fewer problems overall.

I agree. I like to watch cert candidates build motors, especially L1 and L2. In fact the last error that I saw during a cert flight was with a DMS motor where the candidate neglected to insert the washer in the ejection well after drilling the delay.
L3 motors are actually easier to build and now that many require bonding grains to the liner or to each other, which must be done in advance, there’s less opportunity to witness them being built.
 
This is the issue that I have now: The AT I154J-10 deploys 1.9/sec before apogee at about 100ft/sec vert velocity...sounds like a zipper waiting to happen...?

Is there a way to import motor data for motors not in the Open Rocket database? The Aero Tech Master Motor Matrix contains a number of motors i can't simulate because they aren't in the (what seems to be almost completely outdated) database ;( "Data is out of date" Warnings on every motor.
 
Last edited:
If your rocket performance is being modeled accurately, yes. That's an unhealthy speed for a cardboard rocket.

Probably unnecessary sanity checks for sim:
-Final weight and CG location
-Surface finish (OpenRocket)/Cd adjust (Rocsim)
-proper launch altitude and rail length in sim
-parachute deployment settings (first ejection, apogee, etc..)
 
This is the issue that I have now: The AT I154J-10 deploys 1.9/sec before apogee at about 100ft/sec vert velocity...sounds like a zipper waiting to happen...?

Is there a way to import motor data for motors not in the Open Rocket database? The Aero Tech Master Motor Matrix contains a number of motors i can't simulate because they aren't in the (what seems to be almost completely outdated) database ;( "Data is out of date" Warnings on every motor.

It looks like that feature is cleverly hidden under Edit > Preferences > General tab. It appears (and I haven't tested this) that you can automatically import (on OR restart) .eng and .rse engine files that you put in a specific directory. You should be able to find both .rse and .eng files for the motors you're looking for at thrustcurve.org.

But definitely check out Nytrunner's advice. Something also seems fishy in that 1.9 seconds before apogee should be something like 45 ft/s since gravity is only 32 ft/s/s. Normally a +/- 2 second delay is within the normal margin of error, especially for a first flight.
 
I am starting to think that flying an AT H123W-14A (adjusted to 8.5) is a more sensible first flight for DD; A bit faster off the (8ft) rail, nothing spectacular, but just a safe shakedown of a simple DD system. The RRC2-Mini will fire at apogee, the RRC3 +1/sec and the motor charge shortly thereafter.

What say you all? Any red flags?

sim-info.jpg

Super-IV-V2.jpg
 
43.3 ft/sec (13.2 m/sec) close enough?
Close enough, read the post by Bob Krech (actually read everything by Bob Krech) he recommends 30mph for HPR rockets....which happens to be 45fps....

Bob Krech is a VERY knowledgeable rockeeter and scientist (a rocket scientist even) who is very well respected and somewhat missed for his excellent advice (he's still alive, just off working on other retired guy projects).

https://www.rocketryforum.com/index.php?posts/1544248
 
I really miss Bob Krech’s comments on TRF. He was one if the most knowledgeable people here. And he was very kind and patient with the rest of us who were struggling to achieve his mastery of rocketry-related matters.
 
I have been using thrustcurve on my phone to estimate my flight profiles.

I input the data, diameter, weight, mmt, a guess at drag then modify the numbers after a test flight to match the altimeter data.

The app can be a little high on max velocity but the delay prediction has been spot on for me.

Using this a 4" rocket weighing 45oz with the H123w apogee 1380', 61 ft/s rail (86"), and a 6sec delay. H242t 1470', 79'/s, 7sec delay. I154j 2176', 59'/s, 7sec delay. Delay as in time after motor burnout.

Good luck with the cert flight, for a l1 attempt I would run the motor eject and chute release unless you feel confident in the prep process for a full DD rocket. I run my DD rocket using 1 altimeter at apogee and the backup at least +1 sec, you need a delay in consecutive charges, then motor backup after all that, unless it over laps with a electronic event.

~John
 
Last edited:
Back
Top