Apollo 11: Tracing fifty years of the giant leap

On July 20, 1969, just 50 years ago, two astronauts walked on the moon — it was the culmination of the successful Apollo 11 manned moon mission. Neil Armstrong, who took the first steps, described it as ‘a small step for man but a giant leap for mankind’. It was a landmark achievement in humankind’s exploration of outer space.

On that day, an estimated 600 million people around the world sat glued to their TV sets to watch the historic flight and the crew’s first steps on the moon. However, it was a long arduous work of many years which led to success. Close to half a million people worked behind the scenes on the Apollo 11 mission alone. From engineers to ‘human computers’, who included the three African-American women featured in the book and film, Hidden Figures, to scientific administrators, cleaning crews and so many more. It involved a considerable collaborative effort to actually complete this seemingly impossible mission. All those combined efforts bore fruit on that historic day.

About a month before that day, on June 17, leaders across Nasa met at the Kennedy Space Centre for the so-called ‘Flight Readiness Review’ covering every aspect of the launch and mission to see if everything was ready to move forward to the countdown demonstration test. The review was favourable and the test was over, in early July.

The astronauts continued meanwhile to train rigorously. Armstrong and Buzz Aldrin rehearsed their lunar surface extravehicular activity (EVA). On June 16, astronauts simulated the arrival of the ‘Mobile Quarantine Facility’, an airstream trailer that would house the returning lunar crew members putting them in isolation to ensure that they did not bring back any infections from the moon.

Between June 14 and 16, Armstrong had completed eight flights with the Lunar Landing Training Vehicle (LLTV) and finished his training on the craft. He had also completed 12 simulated moon landings in the vehicle. The mission was finally given the green signal when Apollo’s programme director formally announced that Nasa intended to land on the moon, a month later, assuming all pre-flight activities went smoothly.

The Apollo 11 astronauts, Armstrong, Aldrin and Michael Collins, had earlier met and discussed with the astronauts of Apollo 10, which had been a ‘dress rehearsal’ for the moon landing. In that mission, two astronauts in their flight had descended to within 15 km of the lunar surface in the Lunar Module (LM), making them the natural people to consult. Apollo 9 tested the systems in Earth’s orbit while Apollo 8 circumnavigated the moon without landing. All these missions were precursors to Apollo 11.

The Apollo 11 mission finally took off on July 16, 1969, carrying Armstrong, Aldrin and Collins. The giant Saturn V rocket, the most powerful propulsion system so far, weighed over 3,000 tonnes at the start. It burned rocket fuel at the rate of 15 tonnes every second for 160 seconds during the first stage, reaching an altitude of 60 km. So nearly two-thirds of the fuel was used in the first stage, to overcome the Earth’s gravity.

The second stage started with about 800 tonnes, burning fuel for about 400 seconds. After the 90 second burning of the third stage, the Apollo spacecraft was in orbit around the Earth. Its mass in orbit was 150 tonnes. It was now injected into lunar orbit. The transit time to reach the moon was about 70 hours so that the spacecraft arrived in lunar orbit on July 19.

Down to business

Once there, the lunar module (LM) weighing 16 tonnes detached itself from the command module (CM). Armstrong and Aldrin got into the LM to descend to the lunar surface while Collins remained behind in the lunar orbit in the CM. The LM descent engine had twice fired for more than six minutes to descend on the lunar surface. On the final descent, Armstrong noted that the automatic guiding system was guiding the LM, named ‘Eagle’, towards a boulder-strewn crater floor, the size of a football field.

Armstrong took manual control and skimmed over the crater, landing on a flat plain. This was lucky as Eagle had only 50 seconds of fuel left at touchdown. The landing site was in the ‘Sea of Tranquillity’. They landed at the time of early lunar morning when the Sun would be rising on Eagle’s landing site. Apart from avoiding extremes of the lunar day, the morning’s long shadows would help the astronauts identify landmarks. Finally, after nearly 110 hours of launch from Earth, the historic small step took place. Aldrin followed 20 minutes later.

The boot print was photographed to study lunar soil properties. Laser reflectors were left behind to reflect laser beams from Earth. The satellites orbiting the moon today, like LRO, can actually spot the Apollo landing sites from orbit.

After a few hours of rest, there was a crew wake-up call. It was now time for the LM to take off from the moon’s surface and then dock with the CM orbiting the moon (with Collins inside). Soon, the return trip to Earth can begin. However, as during the landing, there were problems prior to lift off. This was crucial because if the LM engine were to fail to ignite or fire for the required duration, the two astronauts could be stranded on the moon forever! (Apparently, they were trained to accept and be prepared for all eventualities!).

Soon after returning to the LM after the moonwalk, Aldrin reported that a crucial engine switch had broken accidentally. But the switch was repaired (Aldrin used something like a ball pen) just one hour before lift-off from moon. Seven minutes after lift-off, the LM was back in orbit, and subsequently, all three astronauts assembled in the CM to return to Earth. They had brought back some 20 kg of lunar rocks and soil. The Russian unmanned spacecraft, Luna 16, 20 and 24 also brought back lunar soil, by automatically taking off from the moon and reaching Earth at a much lesser cost. Of course, it was sans the glamour of a full-fledged manned mission.

The astronauts landed back on Earth, splashing into the ocean at touchdown, eight days after the launch to the moon. It was a one week journey in total. The mission took off with 3,000 tonnes as Saturn V fired its powerful engines. What finally returned to Earth was just six tonnes. There were six more moon landings. Twelve astronauts had the privilege of walking on the moon. The Apollo programme stopped with Apollo 17 in December 1972.

There is currently much activity towards restarting manned moon missions. The Artemis programme is underway and hopes to land astronauts on the moon by 2024, though the costs at $30 billion are forbidding. This doesn’t detract from the fact that 50 years ago, humankind took a giant leap in the exploration of outer space, by landing men on another celestial body for the first time.

(The writer is with Indian Institute of Astrophysics, Bangalore)