Staging, Clustering, and Complexity

Why add complexity?

•  Improve the performance of your rocket •  Meet design specifications •  Fly to greater altitudes (or space) •  Prove your engineering capabilities •  It looks cool •  Impress that special someone

Why avoid complexity?

•  Complexity usually leads to higher costs •  Risk of failure •  Difficulty of design or construction

Staging low-power rockets

Ejection delay timer

Staging

Direct staging of low-power rockets

•  Black powder ignites very easily

•  Motors can be staged using the ejection charge of the booster motor

•  Upper stage motors must be reasonably close to the booster motor to prevent cooling of ejection gases

•  Can also be staged using electronic timers or switches

Gap staging of low-power rockets

•  Very similar to direct staging

•  Add vent holes to allow hot gas to reach the staged motor

•  Vent holes should be no larger than 0.25” in diameter

•  Avoid spacing stages too far apart (>10 inches)

Staging with composite motors

•  Composite motors take a long time to ignite, and thus cannot be directly staged

•  Use electronic staging timer or pre-programmed flight computer

•  Most staging timers work by sending a charge some number of seconds after an acceleration event

•  Remote staging is possible and can prevent unwanted staging events

General staging tips

•  Be sure to couple the stages together, but do not use glue

•  Shear pins are not recommended, either •  Allow components to vent to prevent

premature separation (pinside>poutside)

Staging “Do” and “Don’t”

Do •  Watch your CP/stability

for each stage •  Check all staging timers

and delay timers for the correct values

•  Add vents where necessary

Don’t •  Forget to arm any electric

arming systems •  Use plugged motors for

hot gas method •  Seal off motor mounts

when using direct and gap staging

•  Forget about motor retention

•  Forget about recovery

Why stage?

•  Fly higher (remember Newton’s Second Law) by reducing the mass flown in a given stage

•  Staging is difficult, and thus a good engineering challenge

•  Start small (low power) and work your way up for optimal success

•  Finally put those C6-0 motors to use

Clustering

Clustering

•  Group multiple motors together on the same stage

•  Cluster only BP motors with other BP motors or only composite motors with other composite motors –  Allows all motors in a cluster

to ignite •  BP motors can be clustered

using a clip whip •  Because of high current

draw, composite motors may require ignition by electronics

Clustering “Do” and “Don’t”

Do •  Be mindful of the CG

when adding motors to a cluster (stability)

•  Carefully align all motors to prevent unbalanced moments

•  Carefully install all igniters, plugs, and leads

•  Pay attention to the polarity of a given lead

Don’t •  Cluster black powder

motors with composite motors*

•  Asymmetrically cluster motors

•  Add enough motors to allow the thrust-to-weight ratio to fall below 5

Why cluster?

•  Add more thrust to a single stage •  Boost the altitude capabilities of a rocket •  Induce a spin (flying saucers)

Thrust Vectoring

•  Angling a motor any direction other than directly up the longitudinal axis of your rocket

•  In commercial rockets, useful for stability and control without using fins

•  NAR/TRA frown upon active guidance, so use in a cluster to cancel out unbalanced moments

Experimental Motors

•  Restricted to research launches for Tripoli Level 2 and up, or non-sanctioned launches

•  Requires knowledge of chemistry, thermodynamics, heat transfer, and compressible flow

•  Dangerous to make, but can produce powerful and/or visually interesting propellants

•  Significantly cheaper than commercial motors despite a high start-up cost

•  Significant probability of failure

Experimental Motors