By David Hartman

You are a naval aviator, test pilot, and astronaut. How do you compare those experiences with each other?

They all require dedication, skill, and eternal vigilance. They all involve the acceptance of risk—military combat probably is the highest risk, test flying can involve substantial risk, and space flight requires that you accept some risk.

Which is more fulfilling for you, personally, the challenge of aeronautical engineering or the excitement of flying and being in space?

Both. Engineering is about “what can be.” The world of flight is exploring new dimensions. Flight-testing is that wonderful combination of both to solve the problems of flight in order to expand the boundaries of knowledge and make human flight more extensive, more efficient, and more safe.

You were the youngest of the 12 pilots to fly the X-15. Your seven flights took you to altitude of 39.2 miles and Mach 5.74. How did the X-15 program prepare you for the next steps into space?

The X-15 was a unique research tool—the first to explore the hypersonic region, the first to examine hot structures, and the first to control a craft outside the sensible atmosphere.

The X-1A diverged out of control at 2.4 Mach and the X-2 diverged and was lost at Mach 3. The X-15’s job was to determine stability and control requirements at those and substantially higher speeds. Because the craft could develop such high kinetic energy, it was able to zoom to altitudes well above the atmosphere. That required the development of reaction controls, now common in manned spacecraft. It included the first 3-dimensional inertial navigation system and examined ablative thermal protective techniques.

It truly was a spaceflight innovator and barrier breaker.

Apollo could not have happened without the earlier developmental Mercury and Gemini programs. You flew Gemini 8, the sixth Gemini mission. How significant was the challenge to dock two vehicles and how much was learned from your in-space systems failure?

Simulations of the docking maneuver were quite good. We had questions of whether those simulations accurately modeled both spacecrafts’ reaction when they touched or banged into each other during docking. We wondered whether the environment would affect the operation of the docking mechanism. Confirming our expectations was a very important milestone in our plans for the Apollo Lunar Orbital Rendezvous strategy. It was certainly recognized that systems could fail.

The severe consequences of the Gemini 8 attitude control failure had an immediate effect on control system design and procedures, which affected every subsequent flight.

When you were selected as Commander of Apollo 11, how certain were you that you would actually be the first man to step foot on the moon?

It was not a consideration. At that time we did not know whether Apollo 11 would be able to attempt a landing (the Lunar Module had not yet flown). Simulations and procedural studies for LM exit and entry had not been done.

Later, after those studies were completed, all the Apollo lunar landing flights used the identical method.

When you lifted off in Apollo 11 what did you think, percentage-wise, the chances were that you would walk on the moon and what did you think your chances were of returning to earth, safely?

The greatest unknowns were associated with the navigation and propulsion elements of the descent to the lunar landing, which had not been performed on the previous flights.

There was a substantial possibility that we would run into a problem on the lunar descent, which would require an abort back to lunar orbit and rendezvous with the Command Module. Statistics aside, I felt our chances for getting back to Earth safely were 90 percent and the chances of a successful landing on the first attempt were about even money.

Looking back over your aviation and space experiences, what was most fulfilling about it all for you?

The actual flights in combat, test flying, and space flight are always challenging and memorable.

But the most fulfilling memories are associated with the people you work with, particularly those who made a difference and made the improbable possible.

In my case, there are a lot of those people, and I am in their debt.

–David Hartman is the former host of “Good Morning America.”