Concept Generation Example: Apollo Lunar Module

Summary

• Topic: Concept Generation • Synopsis: The development of the Lunar Module is regarded by many experts as the most technically challenging component of the Apollo program. This case study looks at a few of the specific challenges faced by the engineers involved. Evolution of lander concepts is examined and the viewed through the lens of information available at the time each concept was proposed.

1 Concept Generation Example: Apollo Lunar Module

Photo2 Credit: NASA A Brief History of the Apollo Program

• The Apollo program was designed to land astronauts on the moon • A total of 12 astronauts walked on the moon over the course of 6 manned landings • Timeframe: 1961 – 1972 • Notable missions – Apollo 1 (1967) – all astronauts died in a fire on the launch pad – Apollo 8 (1968) – first manned flight to the moon (orbiting) – Apollo 11 (1969) – first moon landing – Apollo 13 (1970) – oxygen tank explosion leads to dramatic reentry in the lunar module – Apollo 17 (1972) – final manned moon landing

3 Introduction to the Lunar Module (LM) Project

• Regarded by many engineers as the most difficult technical challenge encountered during the course of the Apollo Program: – How to safely descend from orbit, land, and re-ascend a manned craft in the vacuum of space? – Posed an even greater challenge than the development of the Saturn Launch vehicle and Apollo Spacecraft, according to a retrospective analysis conducted by NASA • The development of the LM would push guidance and spacecraft control technologies far beyond anything available when the program initiated Credit: NASA

4 Assumptions & Challenges

• The nature of the problem led engineers to design with the assumption that the craft would need 2 independent propulsion systems: 1 for descent and 1 for re-ascent • Both would need to work perfectly or the astronauts would not return home • Many physical and functional requirements of the craft could not be easily tested or simulated e.g. engine initialization under pre-load in a vacuum Credit: NASA

5 Early Concepts

• British Planetary Society’s Concept – 1939 – Laid the foundation for future LM’s – Module and re-entry incorporated into one vehicle – Developed at a time when only powder rocket technology existed – Perceived design challenge was heat generated during ascent (single vehicle for landing and return) – Heat generated upon atmospheric re-entry was considered trivial, thus the system didn’t include a heat shield for its return to Earth – Thousands of small motors, jettisoned after emptied

Photo Credit: BIS

6 Early Concepts

• Von Braun Lunar Lander – 1952 – Largest of early concepts (3964 metric tons) – More massive than Saturn V booster – Again, Lunar landing and Earth re-entry vehicle combined – To be assembled in Low-Earth Orbit (LEO) over 8 month period – Assembly would require 15 of Von Braun’s hypothesized reusable space shuttles to make a total of 360 trips to LEO, each with a payload of 33 metric tons – Design intent: Group of 3 landers would take a crew of Photo Credit: US 50 astronauts on a 6-week Lunar expedition Information Agency – Propulsive landing drove size (again, aerodynamic braking not yet conceptualized)

7 Apollo LM Development

• Grumman Aerospace (now Northrop Grumman) received the contract to develop the LM in 1962, after the decision to use the “Lunar Orbit Rendezvous Method” was made • Grumman had to agree to utilize and mate up with existing Apollo subsystems where possible • From here, concept generation was largely driven by government and industry studies focused on the best strategies for craft navigation and guidance • As a result of early constraints and newly available information/concerns (e.g. Lunar dust storms that could have been caused by the descent stage), the design evolved heavily between 1962 and 1967 – For example, the diameter of the craft increased from 10ft to 31ft – a major change for such an interrelated and complex system Photo Credit: Northrop

8 Design Evolution

Credit: NASA

Credit: Eric Hartwell

9 System Decomposition (Credit: NASA)

10 Sub-System Decomposition: Landing Gear (Credit: NASA)

• Conceptual Design: Energy Absorption • Challenge – How does one dampen landing of ~15,000kg craft moving at speeds of up to 10ft/s upon landing? • Requirements/early insights: – No hydraulic/pneumatic systems (concern about leakage of fluid into space) – Short stroke to mitigate concerns of bottoming out. E.g. concepts that utilized elastic materials tested poorly – Could be a one-time service, but needed to design for possibility of craft bouncing – No guarantee of even landing surface -> one strut could see all of initial load • Team investigated existing materials for candidates

11 Sub-System Decomposition: Landing Gear Continued (Credit: NASA) • Team found that Hexcell had developed aluminum honeycomb structures that suited their needs • Original purpose was as a rigid, lightweight structure to be used as filler material for aircraft control surfaces • Cylindrical slugs of crushable honeycomb were manufactured for use in strut designs • Energy absorption values from tests were promising; NASA developed piston-cylinder struts customized for use with Hexcell’s aluminum honeycomb cartridges • Need for thick-walled, heavy, complex pneumatic systems was eliminated • Strut performed so well in actual landing that the step down off the LM was longer than expected

12 Looking Forward

• After the cold war between the US and Russia subsided, budgets supporting space exploration began trending downward world- wide • Especially true for funding allocated to manned-spaceflight missions • Such programs, which had previously been a proxy for technological supremacy, began to turn their attention to missions with less abstract forms of financial return – e.g. NASA Astronaut Group 2: Back row: Elliot M. See (died in orbiting laboratories, space telescopes, etc. Gemini training), McDivitt, Lovell, White, & Stafford. Front row: Conrad, Borman, Armstrong, & Young • Today, 8 of the 12 men who set foot on the Credit: NASA moon remain alive • Last human on the moon – 1972 (Apollo 17)

13 Future Missions

• NASA’s manned Mars missions – which experts estimate will cost around $500 billion – are currently scheduled for the 2030’s • In 2014, NASA conducted a successful launch/test of the Orion Multi-Purpose Crew Vehicle (MPCV), which will serve as the launch/splashdown crew delivery vehicle • Significant technology hurdles remain, including entry in to a very thin and shallow Martian atmosphere • In addition, current propulsion technologies could be updated to improve reliability and decrease interplanetary transit time (see Project VASIMR and SpaceX’s Raptor Engine for more)

14 Sources

• http://www.astronautix.com • https://www.nasa.gov • http://airandspace.si.edu/explore-and- learn/multimedia/detail.cfm?id=5205 • http://www.northropgrumman.com • http://heroicrelics.org • Note: Photos are hyperlinked

Credit: NASA

15 Extras

• Interview with Tom Kelly (father of Lunar Module) • Kelly’s Book: http://www.amazon.com/Moon-Lander-Developed- Smithsonian-Spaceflight/dp/1588342735 • Apollo LM Chronology • Apollo News Reference

16 Acknowledgements

• The preparation of this presentation was part of a project funded by the Office of Naval Research (ONR) under Award No. N00014-15-1-2419. The views and conclusions presented are those of the authors and should not be interpreted as representing the official policies, either expressed or implied, of ONR or the U.S. Government.

• The authors appreciate the suggestions provided by Karim Muci- Kuchler, Cassandra Degen, Marius Ellingsen, and Shaobo Huang.

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