X-15: Only One of Three in a Cluster Ignites

[sr205347d]

View attachment X-15 Misfire.m4v

I had at least nine flawless launches prior to this using a cluster of three C6-0 (plugged) motors.

It is a good thing the connectors I use as ignitor clips do not let go and it never got off the rod. It would have been a short flight and a landing in the weeds.

So now I have a 24mm motor mount and plan on using Q-Jet E26 motors. That is a tad less total impulse than the three C6 motors, but also less weight, so the flight performance should be about the same. Will likely need to move the battery aft for balance.

Frank should be happy.

 

[burkefj]

View attachment 602005

I had at least nine flawless launches prior to this using a cluster of three C6-0 (plugged) motors.

It is a good thing the connectors I use as ignitor clips do not let go and it never got off the rod. It would have been a short flight and a landing in the weeds.

So now I have a 24mm motor mount and plan on using Q-Jet E26 motors. That is a tad less total impulse than the three C6 motors, but also less weight, so the flight performance should be about the same. Will likely need to move the battery aft for balance.

Frank should be happy.

I've seen a few too many new Q-jet E-26 motors with burn throughs, or wonky nozzles to trust them in a rocket I cared about, I would just go to the E-6 and have zero risk, plus for the cost, 37.5ns E-6 will get you higher at the same cost per ns. as the the 27.9ns E-26 or a plugged E-12 estes motor. But I'm only basing this on 3500 zero cato flights personally with the E-6's I did consider trying the E-26 but then saw two failures of nozzles at the same launch so didn't.

Glad you didn't leave the rod and look forward to the next report!

Frank

 

[sr205347d]

How long ago were the nozzle failures? Aerotech says they changed the nozzle formulation two years ago.

Post in thread 'Q-Jet E26-7 motor sputtering'
https://www.rocketryforum.com/threads/q-jet-e26-7-motor-sputtering.176525/post-2364150

 

[burkefj]

May of this year

 

[BABAR]

View attachment 602005

I had at least nine flawless launches prior to this using a cluster of three C6-0 (plugged) motors.

It is a good thing the connectors I use as ignitor clips do not let go and it never got off the rod. It would have been a short flight and a landing in the weeds.

So now I have a 24mm motor mount and plan on using Q-Jet E26 motors. That is a tad less total impulse than the three C6 motors, but also less weight, so the flight performance should be about the same. Will likely need to move the battery aft for balance.

Frank should be happy.

Well , you still beat the Mercury-Redstone 1 first flight (4 inches)!

 

[sr205347d]

May of this year

Looking at the MESS reports, all of the date codes are 080321 or earlier.

 

[sr205347d]

I've seen a few too many new Q-jet E-26 motors with burn throughs, or wonky nozzles to trust them in a rocket I cared about, I would just go to the E-6 and have zero risk, plus for the cost, 37.5ns E-6 will get you higher at the same cost per ns. as the the 27.9ns E-26 or a plugged E-12 estes motor. But I'm only basing this on 3500 zero cato flights personally with the E-6's I did consider trying the E-26 but then saw two failures of nozzles at the same launch so didn't.

Glad you didn't leave the rod and look forward to the next report!

Frank

Frank,

Well, the Q-Jet E26 motors have been a headache. See this thread: Q-Jet Follies. Fortunately, no damage has been done, but I have followed your advice and gone to the E6.

Just wondering though, have you considered the E7? The little X-15 doesn't really need to go as high as the E6 will send it, and it is a tad lighter.

 

[burkefj]

Frank,

Well, the Q-Jet E26 motors have been a headache. See this thread: Q-Jet Follies. Fortunately, no damage has been done, but I have followed your advice and gone to the E6.

Just wondering though, have you considered the E7? The little X-15 doesn't really need to go as high as the E6 will send it, and it is a tad lighter.

I haven't simply because the cost for me is only 20 cents cheaper per motor than the E-6 but with 21% less impulse..I have everything balanced for the E-6 motors in my rg's and it's one more thing I'd need to stock, just didn't seem worth it, and for me I'm still able to see them at altitude fine, but if you don't care about that and you want less altitude then try them out it's just a shorter slug of propellent, like the D-7's were.

On the other hand a couple of times people have given me a few packs of those and D-7'sand E-7's and I wound up just cutting one of the slugs into short segments and adding them on top of the E-7 or D-7 propellant grain simply butted together and I'm getting rid of the spacer on the slotted end all together so I get effectively an e6++ or marginal F-6 and they work fine like that, you can hear a little bit of boost increase when you get to the second slug and it hits the new surface area at the grain intersection. I asked Karl about why they had that little short spacer in the e6 to begin with and he didn't really have a good answer it's probably something to do with keeping it in the e range and the 30 g of propellant for shipping but effectively you could create an F-6 reload that's probably 43 Newton seconds total impulse with a full length slug and no spacer. That's effectively what I made.

 

[TheAviator]

I haven't simply because the cost for me is only 20 cents cheaper per motor than the E-6 but with 21% less impulse..I have everything balanced for the E-6 motors in my rg's and it's one more thing I'd need to stock, just didn't seem worth it, and for me I'm still able to see them at altitude fine, but if you don't care about that and you want less altitude then try them out it's just a shorter slug of propellent, like the D-7's were.

On the other hand a couple of times people have given me a few packs of those and D-7'sand E-7's and I wound up just cutting one of the slugs into short segments and adding them on top of the E-7 or D-7 propellant grain simply butted together and I'm getting rid of the spacer on the slotted end all together so I get effectively an e6++ or marginal F-6 and they work fine like that, you can hear a little bit of boost increase when you get to the second slug and it hits the new surface area at the grain intersection. I asked Karl about why they had that little short spacer in the e6 to begin with and he didn't really have a good answer it's probably something to do with keeping it in the e range and the 30 g of propellant for shipping but effectively you could create an F-6 reload that's probably 43 Newton seconds total impulse with a full length slug and no spacer. That's effectively what I made.

The spacer was to keep it at an E6 since the load was designed specifically for us S8 nuts to practice with.

 

[sr205347d]

How about an E20?



View attachment X-15 on E20.m4v

 

[burkefj]

How does altitude compare with an E-6? In my heavier SR-71s it was lower with the E-20 but higher with the F-24

 

[sr205347d]

How does altitude compare with an E-6? In my heavier SR-71s it was lower with the E-20 but higher with the F-24

I would have to do a back to back comparison, but I imagine the E6 would be higher. Besides the total impulse being greater, the lower thrust and speed would mean less drag.

I am just exploring single-use options.

 

[sr205347d]

The second flight was more exciting. It did a barrel roll right off the rod. Don't know why. It scared me, but the spectators thought it was cool.

 

[lakeroadster]

The second flight was more exciting. It did a barrel roll right off the rod. Don't know why. It scared me, but the spectators thought it was cool.

"Yeah, I designed it to do that...."​

 

[TheAviator]

Probably a combo of rod whip and low pitch/yaw damping.

Something similar to that actually plagued real life x-planes. https://en.wikipedia.org/wiki/Inertia_coupling

 

[burkefj]

I've never seen that in over 250 flights of this design personally with E6, D13 and D24 motors but I launch vertically off a 5' rail, maybe rod whip and igniter grab..the E20 is about 10 grams lighter than the E6 so probably not cg related. I'm not smart enough to comment on inertial coupling.

Are you running your guidance? Looks like the rear gets yanked left, not sure what the software would do if using it.

 

[TheAviator]

I've never seen that in over 250 flights of this design personally with E6, D13 and D24 motors but I launch vertically off a 5' rail, maybe rod whip and igniter grab..the E20 is about 10 grams lighter than the E6 so probably not cg related. I'm not smart enough to comment on inertial coupling.

Are you running your guidance? Looks like the rear gets yanked left, not sure what the software would do if using it.

Yeah, the 5 foot rail would make this an absolute non-issue.

 

[sr205347d]

I've never seen that in over 250 flights of this design personally with E6, D13 and D24 motors but I launch vertically off a 5' rail, maybe rod whip and igniter grab..the E20 is about 10 grams lighter than the E6 so probably not cg related. I'm not smart enough to comment on inertial coupling.

Are you running your guidance? Looks like the rear gets yanked left, not sure what the software would do if using it.

Yeah, ignitor grab and subsequent rod whip are the likely culprits. Easy fix for the ignitor grab.

The gyro likely is responsible for it recovering after only one roll. That was much too fast for my old man reflexes.

Here it is in real time.

View attachment Real Time.m4v

 

[sr205347d]

Yeah, ignitor grab and subsequent rod whip are the likely culprits. Easy fix for the ignitor grab.

Looking at the slo-mo in 4K, I don't see much rod motion, but the ignitor wires do get yanked up.