Winston
Lorenzo von Matterhorn
- Joined
- Jan 31, 2009
- Messages
- 9,560
- Reaction score
- 1,749
Building a better strap-on booster (part 1)
by Jeffrey L. Smith
Monday, February 11, 2019
https://www.thespacereview.com/article/3658/1
NGIS has decades of experience building very high-performance composite cases and these are no different, being designed to operate at a pressure of 1,450 psi. Because rocket engineers are a conservative lot, they actually build the case thicker to hold 40 percent more pressure, some 2,030 psi. And just to be paranoid, before going out the door, each case is filled with water and pressurized to 25 percent above the design pressure (1,813 psi) and checked for leaks. The high internal pressure allows the motor to be fitted with an efficient 14-to-1 expansion ratio nozzle made of carbon phenolic. By comparison, the Space Shuttle’s SRBs operated at just 900 psi and so could only be fitted with a 7.7-to-1 expansion ratio nozzle.
The biggest challenge of this effort has been to reduce cost, and the technical decisions reflect this. In aerospace, cost doesn’t scale with size but rather with complexity, and decisions have been taken at every turn to reduce complexity and simplify the design. Instead of a high-priced and complex 3D carbon-carbon throat or a thrust vector control (TVC) system, the GEM 63 features a simple and low-cost carbon phenolic that does not move. This shows a preference for low cost and simplicity over strict performance.
Graphite-Epoxy Motor
https://en.wikipedia.org/wiki/Graphite-Epoxy_Motor
GEM 63/GEM 63XL brochure
https://www.northropgrumman.com/Capabilities/GEM/Documents/GEM_63_GEM_63XL.pdf
The GEM 63 motor case being lowered into the casting pit before the propellant is poured in. The motor has to be moved in a diagonal position because it’s too tall for the building:
https://www.thespacereview.com/archive/3658d.jpg
https://www.thespacereview.com/archive/3658g.jpg
by Jeffrey L. Smith
Monday, February 11, 2019
https://www.thespacereview.com/article/3658/1
NGIS has decades of experience building very high-performance composite cases and these are no different, being designed to operate at a pressure of 1,450 psi. Because rocket engineers are a conservative lot, they actually build the case thicker to hold 40 percent more pressure, some 2,030 psi. And just to be paranoid, before going out the door, each case is filled with water and pressurized to 25 percent above the design pressure (1,813 psi) and checked for leaks. The high internal pressure allows the motor to be fitted with an efficient 14-to-1 expansion ratio nozzle made of carbon phenolic. By comparison, the Space Shuttle’s SRBs operated at just 900 psi and so could only be fitted with a 7.7-to-1 expansion ratio nozzle.
The biggest challenge of this effort has been to reduce cost, and the technical decisions reflect this. In aerospace, cost doesn’t scale with size but rather with complexity, and decisions have been taken at every turn to reduce complexity and simplify the design. Instead of a high-priced and complex 3D carbon-carbon throat or a thrust vector control (TVC) system, the GEM 63 features a simple and low-cost carbon phenolic that does not move. This shows a preference for low cost and simplicity over strict performance.
Graphite-Epoxy Motor
https://en.wikipedia.org/wiki/Graphite-Epoxy_Motor
GEM 63/GEM 63XL brochure
https://www.northropgrumman.com/Capabilities/GEM/Documents/GEM_63_GEM_63XL.pdf
The GEM 63 motor case being lowered into the casting pit before the propellant is poured in. The motor has to be moved in a diagonal position because it’s too tall for the building:
https://www.thespacereview.com/archive/3658d.jpg
https://www.thespacereview.com/archive/3658g.jpg
