Original Little Joe Rocket footage motor Sequencing

The Rocketry Forum

Help Support The Rocketry Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Astronot

Well-Known Member
Joined
Sep 27, 2013
Messages
295
Reaction score
0
I was watching some flight footage of the Little Joe today and noticed that when launched, all four Sergeant motors were burning full throttle, and then several seconds into flight, it appears two of the solid rocket motors were essentially shut down to the point where just a lazy flame was coming out of them and then quite a few seconds later, the throttled back motors, would come back up to full thrust in what seem like a planned sequence. I was wondering if any of you knew or understood how that was accomplished and why they did it that way instead of letting all four burn at full thrust.

Thanks,

David
 
Maybe it wasn't suppose to happen that way. Where Sergeant Motors prone to doing that?

David
 
Do you know which Little Joe flight it was? The flights had different combinations of motors firing at different times to produce the desired flight profile. I believe in one or two of the earlier flights they had a problem with auto ignition that had motors firing early. Since there were eight motors it's possible you were seeing one set of motors firing after the first set burned out. Here's an excerpt from A New Dimension. Wallops Island Flight Test Range: The First Fifteen Years page 636.

A boilerplate capsule was quickly made ready for a flight to qualify the Little Joe booster since, in
the first attempt, the booster was not fired. This uninstrumented capsule, designated LJ-6, was
launched about 6 weeks later, on October 4, 1959. The only flight event planned other than the boost
phase was the activation of the destruct system by ground command. The capsule was attached to the
booster with a Marman clamp, but the escape motor was merely a ballasted empty case. This flight was
made with four Pollux and four Recruit motors in the booster case. The launching was normal, and the
Little Joe booster flew a stable trajectory, but there was a premature firing of two of the Pollux motors.
In the Little Joe system, either the four large motors could be ignited at launch or they could be fired in
two stages to provide different flight conditions. In this flight, two Pollux motors were ignited along
with the four Recruit motors at launch, and the other two Pollux motors were programmed to fire 24.5
seconds afterward. In the actual flight, however, one of the second set of motors fired at 9 seconds and
the other at 18 seconds after launch. It was concluded that circulation of the hot exhaust gases within
the base area of the booster melted the polystyrene nozzle pressure seal closures and then ignited the
motors. The destruct system was activated by radio command 170 seconds after launch, and the system
apparently worked as planned (ref. 34).


My favorite piece of Little Joe trivia. Who invented the Marman clamp?
 
I was watching some flight footage of the Little Joe today and noticed that when launched, all four Sergeant motors were burning full throttle, and then several seconds into flight, it appears two of the solid rocket motors were essentially shut down to the point where just a lazy flame was coming out of them and then quite a few seconds later, the throttled back motors, would come back up to full thrust in what seem like a planned sequence. I was wondering if any of you knew or understood how that was accomplished and why they did it that way instead of letting all four burn at full thrust.

Thanks,

David

Some were airlit... sequential burn to get the desired performance...

I posted a study on the Little Joe in the scale section... including a Lunar Module test version of Little Joe that never flew...

Later! OL JR :)
 
Forget that. Is Zeppo really your favorite?

I can honestly say I don't have a favorite Marx brother.

Kenn assumes I would like the least funny of them because there are some things he finds hilarious that I think are mildly humorous. I was the victim of a CMASS intervention where he and a couple other members forced me to watch The Princess Bride and Monty Python. While each had a few good lines, I feel that my life would have still been complete if I hadn't seen them.
 
I can honestly say I don't have a favorite Marx brother.

Kenn assumes I would like the least funny of them because there are some things he finds hilarious that I think are mildly humorous. I was the victim of a CMASS intervention where he and a couple other members forced me to watch The Princess Bride and Monty Python. While each had a few good lines, I feel that my life would have still been complete if I hadn't seen them.
Don't forget to mention that you now occasionally quote both The Princess Bride and Holy Grail.
 
Back
Top