The main concern with the proposed design was potentially

yielding the rocket motor ring. To determine whether or not this

could occur during operation, an analysis was performed using

FEA calculations on Solidworks, as seen in Figure 7. With the

proposed solution, the design is expected to maintain a factor of

safety far greater than the desired 3.0 with respect to yielding the

motor ring. [2].

The team also needed to determine the torque necessary to apply

and test the adhesion of the standoffs using a power screw. From

equations (1) and (2), the torque to raise and lower was

approximated to be .313 and .176 lbf-ft respectively [3].

(1)

(2)

The entirety of the design displayed in Figure 8 was

manufactured in the 98C machine shop. The majority of the

device was created by the capstone team using the mills and

lathe machines available to students. Some parts that required

complex geometry, such as the motor clamp pieces, required the

machine shop managers to create using the CNC. The bulk of the

design was constructed of Aluminum 6061 with a stainless steel

lead screw, brass nut and aluminum screws/bolts.

Northrop Grumman Standoff Bonding Device

Department of Mechanical Engineering, Northern Arizona University, Flagstaff, AZ 86011

Brandon Bass, Tyler Hans, Sage Lawrence, Elaine Reyes, Dakota Saska

Rocket motor integration activities at Northrop

Grumman field sites bond standoffs (threaded

mounting devices that are used to mount avionic

electrical components) using long sure adhesives to

rocket motor domes of various geometry. The

standoffs are held by metal brackets, which are

taped to the motor dome for up to 72 hours to allow

for curing of the adhesive. This method is unreliable

and fails roughly 5 percent of the time resulting in

either the brackets slipping or falling off the motor

domes. An increase in man hours is incurred when

the taping method fails; this costs time and money

when installing these standoffs. For this reason,

Northrop Grumman’s Flight Systems Group has

requested for our team to design, analyze, and build

a prototype universal dome standoff bonding tool

that can be mounted to the attach rings of several

variations of rocket motors that will hold standoff

brackets in place while the adhesive cures.

Abstract Conclusion

The goal of the Northrop Grumman standoff project was to design, analyze,

and build a prototype articulating bonding tool. The team was able to

complete all these goals before spring break, although some improvements

to the design would have been made if more time was available. Due to the

limitations imparted by COVID-19, the team was unable to complete the

testing of the device to the desired standard. Based on initial testing before

spring break and analyses performed by the team through the school year,

the device is expected to perform all design activities with a minimum factor

of safety of 3.

References

[1] Propulsion Products Catalog, Northrop Grumman, Falls Church, VA,

June 2018

[2] “Aluminum Alloys - Mechanical Properties,” The Engineering Toolbox,

2008. [Online]. Available:

https://www.engineeringtoolbox.com/properties-aluminum-pipe-

d_1340.html. [Accessed: 18-Oct-2019]

[3] R. G. Budynas and J. K. Nisbett, Shigley's Mechanical Engineering

Design, New York: McGraw-Hill, 2011.

Acknowledgements

Dr. Sarah Oman, Daniel Johnson, 98C Machine Shop, Perry Woods, Tyler

Trebilcock and Derek, and Northrop Grumman

Design Requirements and

Approach

SubassembliesSub

Analysis and FabricationThe mounting arm is required to:

- Support brackets bonded 4-36 inches inboard

from the motor ring

- Have 6 degrees of freedom

- Be ESD (electrostatic discharge) compliant

- Perform a pull test of 50 lbs at 45 deg. of freedom

- Maximum deflection of .1” for rail design

- Be adaptable to several mounting bracket

templates

- Hold a bracket to up to 10 lbs

- Lock in place and apply a force of 20 lbs

- Have a Factor of Safety of 3.0 based on

maximum expected loads

- Be easily manipulated by hand

- Allow the use of multiple mounting arms at a time

- Be mountable to several rocket motors

Figure 1 displays one of the rockets that the

standoff bonding tool will be designed for.

Pictured left are four of the five

main subassemblies for the final

design. Clamp to Motor Ring

(Fig. 2), Angling Mechanism

(Fig. 3), Rail System (Fig. 4),

Rail Rart (Fig. 5). The final

subassembly which holds the

standoff templates directly was

not finished before the impact of

Covid-19 reached campus. This

final assembly can be seen in

the finalized CAD image in

Figure 6. This assembly would

be fully adjustable to adhere to

the many template dimensions.

It would have another angling

mechanism to match the face of

the motor dome as normal as

possible to ensure proper

adhesion of the standoffs.

Figure 2. Motor Ring Clamp Figure 3. Angling Mechanism

Figure 4. Rail System Figure 5. Rail Cart

Figure 8. Final Product

Figure 6 Final CAD Model

Figure 7. Ring Moment FEA

Figure 1. Castor 50XL [1]