Aerospace Engineering Technical Architecture 1962 Historical

How to Reach the Moon

Apollo Program Mission Architecture Decision

Context

The U.S. space program in the 1960s had a single, ambitious goal: land a man on the moon and return him safely to Earth before the end of the decade.

Challenge: The decision on how to achieve this was one of the most complex technical and logistical problems of all time.

Deadline: End of the 1960s decade

Direct Ascent

Send one massive rocket directly from Earth to the moon and back.

Risk
high
Complexity
low
Feasibility
low

Advantages

  • Simpler mission profile
  • No complex orbital maneuvers
  • Single launch vehicle

Disadvantages

  • Required a rocket far larger than any existing at the time
  • Development highly uncertain
  • Massive engineering challenges
  • Extremely heavy payload requirements

Earth Orbit Rendezvous (EOR)

Launch multiple rockets, assemble them in Earth orbit, and then fly the completed spacecraft to the moon.

Risk
high
Complexity
high
Feasibility
medium

Advantages

  • Used existing rocket technology
  • Distributed payload across multiple launches
  • Modular approach

Disadvantages

  • Logistically complex
  • High risk from multiple launches
  • Risky docking maneuvers in orbit
  • Coordination challenges
Chosen Solution

Lunar Orbit Rendezvous (LOR)

Send a single spacecraft to the moon, where it would split into two parts. The small 'lander' would descend to the surface while the 'command module' orbited. After the moonwalk, the lander's ascent stage would blast off and rendezvous with the command module for the return trip.

Risk
medium
Complexity
medium
Feasibility
high

Advantages

  • Much smaller and lighter spacecraft needed
  • Feasible with existing rocket technology
  • Shaved years off the timeline
  • Most technically efficient solution
  • Reduced fuel requirements

Disadvantages

  • Required perfecting complex docking in lunar orbit
  • Never been done before
  • Technically risky
  • Faced significant opposition

Lunar Orbit Rendezvous (LOR)

Despite significant opposition, particularly from Wernher von Braun and his team who favored Direct Ascent, NASA's engineers ultimately chose the Lunar Orbit Rendezvous (LOR). This was a technically risky decision because it required perfecting a complex docking maneuver in lunar orbit, something that had never been done. However, it was also the most elegant solution. LOR required a much smaller and lighter spacecraft to land on the moon's surface, which was a huge advantage given the limitations of rocket technology at the time. It made the entire mission feasible with existing rockets and shaved years off the timeline.

Systems-level thinkingTechnical efficiency over perceived simplicityTimeline constraintsRocket technology limitations

Outcome · Success

The decision was vindicated with the success of the Apollo missions. LOR was the only viable path to meet President Kennedy's deadline.

Proof: The successful rendezvous of the lunar module with the command module in orbit around the moon, a maneuver that saved the lives of the Apollo 13 crew, proved the wisdom of this choice.

This decision highlights the importance of systems-level thinking and choosing the most technically efficient solution, even if it appears more complex on the surface.