Quantcast

Queston on staging - gap between motors

The Rocketry Forum

Help Support The Rocketry Forum:

JRobinsonUSAF

Active Member
Joined
Dec 20, 2011
Messages
31
Reaction score
0
What would be considered the largest acceptable gap between the top end of a “D” booster motor and the nozzle of a “D” sustainer nozzle to ensure ignition. I am looking at a scale/semi-scale two stager that, if built to specs, would leave a 3 inch gap between the two motors. Is this wishful thinking, or would I be able to get second stage ignition?
 

tsai

Well-Known Member
Joined
Jul 23, 2010
Messages
254
Reaction score
10
I have a rocket with an 8" gap between. Use a small vent hole near the second stage to prevent separation from the pressure. 3" should be no problem.
 

rharshberger

Well-Known Member
Joined
Oct 13, 2014
Messages
9,706
Reaction score
1,685
Location
Pasco, WA
What would be considered the largest acceptable gap between the top end of a “D” booster motor and the nozzle of a “D” sustainer nozzle to ensure ignition. I am looking at a scale/semi-scale two stager that, if built to specs, would leave a 3 inch gap between the two motors. Is this wishful thinking, or would I be able to get second stage ignition?
Gap staging can be reliably done up to 10", its a good idea to put a vent port near the upper motor to prevent early seperation. I have successfully gap staged 8" with zero failures over the 10 or so flights with my rocket that uses it.
 

kjohnson

mox nix
Joined
Jan 19, 2009
Messages
1,300
Reaction score
4
Are you talking about a 3" gap with nothing in between, or a 3" gap that allows for some sort of tubing to direct the hot gas and particles from the booster to the sustainer?
What's the prototype?

kj
 

JRobinsonUSAF

Active Member
Joined
Dec 20, 2011
Messages
31
Reaction score
0
Are you talking about a 3" gap with nothing in between, or a 3" gap that allows for some sort of tubing to direct the hot gas and particles from the booster to the sustainer?
What's the prototype?

kj
The gap would be within a tube the same size as the motor (BT-50), between the top of the booster and the nozzle of the sustainer.

JR
 

kjohnson

mox nix
Joined
Jan 19, 2009
Messages
1,300
Reaction score
4
Yes that will work fine. As others have said, put a hole in the top of the connecting tube, just below the bottom of the upper stage motor.

kj
 
Top