Space Sunday special: Apollo 11 at 50

NASA’s official Apollo 11 50th anniversary logo. Credit: NASA

This week sees the 50th anniversary of the Apollo 11 lunar landing. To mark the event, this Space Sunday article and the next will look at that mission, and the three men who flew it.

Part 1: “Lift-of We Have Lift-off!”

On Wednesday, July 16th, 1969, at 13:31:51 UTC (9:31:51 EDT) five Rocketdyne F-1 at the base of Saturn V SA-506 came to life. Starting with the centre motor, then the opposing outboard pairs, the entire ignition sequence took 600 milliseconds. Held on the pad by four massive clamps, called hold-down arms, the five engines gradually built up thrust to 35,100 kN (7,891,000 lbf).

At precisely 13:32:00 UTC) (9:32:00 EDT) the huge hold-down-arms rocked back in a “soft release”, allowing the rocket, weighing almost 3,274 tons, to start its ascent, its acceleration slowed for the first half-second by a series of 8 pins connecting it to the pad to “reduce transient stresses resulting from abrupt disengagement of a vehicle from its launch stand”. When these pins dropped free from the base of the rocket, Apollo 11 was on its in a historic mission that would seen humans land on the Moon for the first time.

Apollo 11, May 20, 1969, on Flickr
Saturn V SA-506, the Apollo 11 launch vehicle, is rolled out to Pad A at Launch Complex 39 at Kennedy Space Centre, May 20th, 1969

The two men destined to be the first to set foot on Earth’s natural satellite were Neil Alden Armstrong, just shy of his 39th birthday, and  Edwin Eugene “Buzz” Aldrin Jr., who had turned 39 in January 1969, sat atop of the massive Saturn V rocket along with Command Module Pilot, Michael Collins, the youngest of the three (if only by a couple of months). Together, they formed only the second Apollo flight crew where all three men had previously flown in space (the first having been Apollo 10, the “dress rehearsal” mission for the Moon landing).

Armstrong, Aldrin and Collins were also perhaps the most technically competent trio on NASA’s astronaut roster at the time. All had served in the military – Armstrong in the US Navy, Aldrin and Collins in the US Air Force. Both Armstrong and Collins had also built up impressive résumés as test pilots, Armstrong as a civilian and Collins in the US Air Force.

In particular, Armstrong flew with the National Advisory Council for Aeronautics (NACA), NASA’s forebear, prior to being selected for the USAF/ NASA high-altitude X-15 research programme, (he flew the X-15 seven times between late 1960 and mid-1962) whilst simultaneously engaged by the USAF in their X-20 Dyna-Soar space plane project. Collins, meanwhile, took part in high-altitude flights, taking F-104 Starfighter jets to 27.7 km (90,000 ft) in order to experience the “weightless” environment of free-fall at the top of their parabolic flight arcs, helping him to achieve 3,000 hours in the cockpit.

Collins, Aldrin and Armstrong, on Flickr
An unusual portrait in black and white of Michael Collins, Edwin “Buzz” Aldrin and Neil Armstrong. Credit: NASA (this image was later colourised on numerous occasions by various artists)

As well as being aviators, Armstrong and Aldrin were also academics. Armstrong held a BSc in aeronautical engineering and an MSc in aerospace engineering, and Aldrin has a doctorate in astronautics. Aldrin particularly specialised in on-orbit rendezvous, which allowed him to work on Project Gemini as an engineer (and also earned him the nickname “Dr. Rendezvous” , not always meant kindly, by other astronauts).

Despite their qualifications, both Armstrong and Aldrin almost didn’t get selected for NASA’s astronaut programme: neither had the requisite military test pilot qualifications that were initially required. However, in 1962, NASA dropped the “military” element from the test pilot requirement, enabling Armstrong to apply for the Group 2 intake – although he almost missed the cut. his application arrived after the closing date, but fortunately Dick Day, a simulations engineer at NASA who have previously worked with Armstrong saw the application and made sure it was included.

Aldrin’s break came in 1963, when NASA further revised the requirements to test pilot OR 1,000 hours flying jets. This allowed he to re-apply (his first application having been turned-down due to his lack of test pilot experience), and he was invited to join the Group 3 intake alongside Michael Collins.

At 2 minutes 41 seconds into its flight, the S-IC first stage of Apollo 11 separates, four small separation motors pushing the upper stages way from it, prior to the S-II second stage main engines to ignite

A Saturn V launch is perhaps one of the most stunning sights to witness – and Apollo 11 was witnessed by around 1 million people in and around the Kennedy Space Centre. However, for the first part of their flight, the three men were pretty much passengers as the Saturn V rose into the sky.

For all their power, the five F-1 engines took 12 seconds to overcome the 100.6 m tall rocket’s mass and inertia and push it clear of the 120m tall Launch Umbilical Tower (LUT), angling it very slightly away from the tower in the process so to avoid the risk of any wind-driven contact between the two.

Immediately after clearing the tower, the rocket commenced its “roll”, a necessary manoeuvre in which the vehicle rolls around its vertical axis, allowing it to point itself along the line of flight it needs to achieve the required orbit. After that, things started to move quickly.

A minute after launch, the Saturn V was around 6.5 km (3.5 nautical miles) altitude and passing through the sound barrier. Twenty seconds later, it entered “Max Q”, the period of maximum dynamic pressure, placed on this frame as a result of it literally punching its way through the atmosphere.

At this point, the F-1 engines throttled back a little to prevent the vehicle shaking itself apart, but once through “Max Q” – a period of only a handful of seconds, they returned to full thrust, pushing the vehicle up to 62 km (42 mi) above the Earth, and taking only 2 minutes 41 second from launch to do so. At this point, and travelling at 9,960 km/h (6,164 mph), the huge first stage separated, the upper stages of the Saturn 5 pushed clear by a set of four separation motors.

From here, the four motors of the second stage took over. While the massive first stage coasted upwards behind it and then fell back to crash into the Atlantic ocean, the Second stage ran for 6 minutes, accelerating the rocket to 25,000 km/h (15,647 mph) and lifting it to an altitude of 175 km (109 mi).

With its fuel spent, the second stage separated, also to fall back to the Atlantic, while the single, re-usable engines of the all-important S-IVB stage took over. This stage initially ran for about 2.5 minutes, during which time it pushed Apollo 11 to a velocity of 27,900 km/h (17,432 mph), allowing it to assuming a near-circular orbit around the Earth averaging 184 km 98.9 na mi) before shutting down for the first time.

It was at this point that the three crew took a more pro-active role in the flight. For the next  couple of hours, as they completed 1.5 orbits of the Earth, and in tandem with mission control, they confirmed their vehicles were ready to be committed for the flight to the Moon.

Apollo 11, May 20, 1969, on Flickr
A diagram of the Saturn V Apollo launch vehicle.Credit: NASA

Interestingly, while mission commander, Armstrong had actually clocked less time in space than either Collins or Aldrin. However, he had the greatest experience in handling in-flight emergencies, having dealt with the first in-flight failure of a critical system during a US space mission.

Neil Armstrong photographed by Buzz Aldrin as the crew prepare for TLI – trans-lunar injection. Credit: NASA / E.E. Aldrin

This occurred during his flight flight into space on the Gemini 8 mission, alongside David R. Scott. This mission was intended to be the first test of an orbital docking between two vehicles – Gemini 8 and an automated Agena target vehicle. In all, Armstrong and Scott were expected to complete four such docking as a part of the mission objectives.

However, shortly after docking, the Gemini’s Orbit Attitude and Manoeuvring System (OAMS) has suffered a serious failure, and Armstrong ordered Scott to release the docking mechanism before before vehicle broke up. Once free of the Agena (which was later stabilised by ground control allowing it to be used by Gemini 10 with Michael Collins), Armstrong took the took the unorthodox step of shutting down the OAMS and using the Re-entry Control System (RCS) to regain control. While this worked, undoubtedly saving his and Scott’s lives, under mission regulations, they no option but to immediately perform and emergency return to Earth, curtailing the mission.

Back aboard Apollo 11, their checks complete, the crew received the all clear for the critical trans-lunar injection (TLI) burn. This started mid-way through the second orbit of Earth, as the S-IVB motor was restarted and fired for 5 minutes and 47 seconds, accelerating the vehicle to around 40,085 km/h (25,053 mph), and pushing it away from Earth and into an energy-efficient trajectory towards the Moon.

The Apollo 11 LEM, call sign Eagle, on FlickrAs Michael Collins carried out the transposition, docking and extraction manoeuvre, either Aldrin or Armstrong took this image of the Lunar Module (LM) sitting in the top of the Saturn V S-IVB stage, awaiting the Command and Service Module (CSM) to dock with it and gently pull it free of the upper stage. Credit: NASA

Thirty minutes after the TLI burn, the crew were set for another critical manoeuvre, one essential to the Moon landing: the transposition, docking, and extraction (TDE) manoeuvre: extracting the Apollo Lunar Module from the Saturn V’s upper stage.

An incredibly delicate vehicle (designed to operate in the vacuum of space and the lunar gravity environment (1/6 that of Earth’s), the Apollo Lunar Module flew aboard the Saturn V mounted with its legs folded against itself like insect legs, in a special cradle at the “top” of the S-IVB stage. Four sloping and tapered adapter panels enclosed it during launch and ascent to orbit, panels which also connected the Command and Service Modules to the rest of the rocket.

For TDE, Michael Collins, as Command Module Pilot, had to separate the CSM from these adapter panels, all four of which would also separate from the S-IVB stage. Using the Service Module’s manoeuvring thrusters, he moved the CSM combination some 15 m (50 ft) ahead of the S-IVB stage before rotating it through 180° (the “transition”) so the Command Module was facing the exposed Lunar Module.

The Apollo CSM-LEM TDE, on Flickr
Left: How the CSM and LM are stacked within the Upper part of the Saturn V, above the S-IVB third stage. Right: the TDE manoeuvre. Note in this digram, the adopter petals are shown as remaining attached to the S-IVB stage. In actual fact, they were completely jettisoned. Credit: NASA

Then, with a gentle application of the thrusters, he reduced the distance between CSM and LM, using target indicators to align the docking mechanism in the nose of the Command Module with the docking receptacle on the top of the LM. Following a successful docking, Collins again used the CSM’s thrusters, this time easing it away from the S-IVB, pulling the secured LM with it (the “extraction”).

Collins continued to ease the CSM/LM combination away from the S-IVB until the distance was judged to be safe enough for mission control to order the S-IVB to complete a small course correction. This allowed the stage to gradually diverge away from the path the CSM/LM was taking to the Moon. This course correction also allowed the S-IVB to pass by the Moon and continue on into a heliocentric orbit around the Sun. In doing so, its became only one of two Apollo S-IVB stages that carried men to the Moon to do so, the other being Apollo 10’s upper stage. (For the record, Apollo 12’s S-IVB ended up in and extended Earth orbit, while the upper stages of Apollo missions 13 through 17 were all deliberately crashed into the Moon so their impacts could be measured by the seismometers deployed deployed during the Apollo 12, 14, 15 and 16 missions as part of the Apollo Lunar Surface Experiment Package, helping scientists to understand the Moon’s internal structure.)

A CGI model of the Apollo Command and Service Module (l) and Lunar Module combination as they would have appeared during the cruise phase to the Moon. Note that the Lunar Module’s folded landing legs. With the exception of Apollo 13, the legs were not extended to their landing position until after the vehicles had arrived in lunar orbit and the LM had been powered-up in preparation for its descent to the Moon’s surface. Credit: unknown

For Collins, Aldrin and Armstrong, the completion of TDE marked the end of the intensive “launch phase” of the mission and the start of their 3-day “cruise phase” to the Moon.

Continued in: Part 2: “The Eagle has landed!”

In Brief

Virgin Orbit Completes Drop Test

Virgin Orbit performed a key test of its LauncherOne air launch system on Wednesday, July 10th, dropping an inert vehicle from its carrier aircraft.

The modified 747 carrier vehicle, Cosmic Girl, took off from the Mojave Air and Space Port in California in the early hours of the morning, and climbed to 10,700 m (34,775 ft). Under its wing was a dummy LauncherOne rocket, filled with water to simulate a full fuel load and a 330 kg (660 lb) payload.

once at altitude, the carrier aircraft released the dummy rocket as it would during an actual launch, allowing data to be gathered on the drop / glide dynamics of a fully laden LauncherOne. During an actual launch, the rocket would fall clear of the carrier before igniting its motor to accelerate away and climb to orbit. However, for this test, the inert rocket simply fell to the ground within a designated test range at Edwards Air Force Base, California.

Regarded as a success by Virgin Orbit, the drop test signals the end of the LauncherOne / Cosmic Girl flight test programme. The company is now finalising assembly of the first operational LauncherOne rocket. This will then go through a series of ground tests before undertaking the first orbital launch attempt “later in 2019”.

SpaceX Starship Test Vehicle Set to Fly

Elon Musk has announced that the Starhopper – the scaled test article for SpaceX’s planned Starship launch vehicle – is set to make its first untethered powered flight on July 16th, 2019, the 50th anniversary of the launch of Apollo 11.

While the Moon is one of the intended destination for the full-scale Starship vehicle, designed to be launch with the SpaceX Super Heavy booster, the first flight will be far more modest, “We’ll go about 20 metres up and then sideways,” Musk stated on Twitter.

The Starhopper, much smaller than the actual Starship, has thus far only completed a very brief (and tethered) “hop” whilst undergoing tests in Texas during April. The July 16th flight, however, will see the vehicle ascend and manoeuvre without any tether. If this, and the flights that follow are successful, Musk indicated he expects SpaceX to fly “Starship MK 1” to altitudes of up to 20 km “within a few months”.

The Texas Starhopper is one of two such vehicles; the company is building a second in Cocoa, Florida, near Cape Canaveral, but there are no details on when it will be ready to fly.

SpaceX is building a second Starhopper text vehicle in Florida. Credit: SpaceNews / Jeff Foust

 

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