List of illustrations

Colour section between pages 188 and 189. Full Earth, as seen from Apollo Sketches from October I960 for the Apollo-Control Capsule 6 President Kennedy announces his lunar challenge to Congress 7 Apollo 14 CSM Kitty Hawk in orbit around the Moon 8 Wernher von Braun beside an early Saturn launch vehicle 9 John Houbolt of Langley, the champion of LOR 10 Computer rendering of the Apollo command module 12 Cutaway of the command module Computer rendering of the command module instrument layout 13...

Every last drop

Soon after the centre engine had shut down as planned on Apollo 16, and as they approached the final minute of the S-II's flight, the crew felt a slight, but expected drop in thrust. ''PU shift,'' called out John Young, the mission's commander. ''Sixteen, Houston. We saw the PU shift. Thrust looks good, and you're Go for staging,'' replied Gordon Fullerton, the launch Capcom. What was shifting was a valve in each engine that controlled the flow of LOX to the combustion chamber. This was the...

Which

Even as Kennedy announced that the Moon would be the destination for America's aerospace community, managers still had to decide how to make the trip. At first, two competing methods, or modes, were investigated, both of which had powerful advocates and detractors. A third plan struggled for attention and was often mocked. The first plan was known as direct ascent, and though it appeared at first glance to be the simplest solution, it was the most audacious of all. It entailed the development...

SPS the engine that just had to work

The SPS engine was mounted at the rear of the central tunnel, below the helium tanks. This was the one major engine in the Apollo system that had to be capable of being regularly restarted from the point of view of crew safety. Failure to operate at its first major firing to enter lunar orbit could be tolerated, because the spacecraft would loop behind the Moon and return to Earth's vicinity. Other engines could then restore a trajectory home. However, a spacecraft already in lunar orbit was...

The crew arrive

Having had a hearty but low-residue breakfast in the crew quarters located some kilometres south of the VAB, the prime crew moved on to the suiting-up room where a covey of technicians helped them to don their spacesuits. These would protect them if they left the spacecraft for a planned venture outside, or if the cabin were to become unexpectedly depressurised. Careful checks were made to ensure that their suits were airtight (checking the pressure integrity in NASA parlance) before the crew...

Further reading

As a topic, space history and the Apollo programme in particular are quite well represented in print and on the World Wide Web. Below is a list of books and web resources which are recommended for any reader wishing to delve further into the programme. A Man on the Moon The Voyages of the Apollo Astronauts, Andrew Chaikin. Viking Penguin Inc., 1994. Angle of Attack Harrison Storms and The Race to the Moon, Michael Gray. W.W. Norton & Co., 1992. Apollo, Alan Bean. Greenwich Workshop Press,...

RCS consumable management

Although the Apollo spacecraft was a truly amazing machine for its time, it was, in many ways, extremely marginal. Only by the very careful husbanding of all the consumables it carried could a mission be completed. There was little room for error or excess. However, it was sometimes difficult to measure how much of a resource was being consumed. Hydrogen and oxygen were relatively easy. The tanks had sensors to directly measure quantity, the flow of these two elements to the fuel cells was well...

The Tei Pad a worked example

Of their thirtieth revolution around the Moon. The second was in case the SPS engine failed to light at the first opportunity, in the hope that it would light next time around. TEI-30, started Duke. SPS G& N 36691, minus 061, plus 066, 135234156. Noun 81 32 - correction - plus 32011, plus 06818, minus 02650 181 054 014. Apogee is N A, perigee plus 00230 3286 - correction - 32836 burn time 228 32628 24 1511 357. Next three lines are N A. Noun 61 plus 1103, minus 17237 11806 36275 1950452. Set...

Ejection freeing the lander

Apollo Tunnel Docking Mechanism

The final stage of the TD& E process was the ejection of the lunar module from the top of the S-IVB, which was not a simple process of just throwing a switch and watching it happen. Throwing the switch would come at the end, but first, they had to get the signal from the switch in the CM, down past the LM to the pyrotechnically fired spring thrusters that pushed the LM free. That meant that the CMP had to connect two umbilical cables that ran power and signals between the two spacecraft....

The Loi Pad It Isnt Magic

While the crew conducted their checks, engineers on Earth carefully measured the effect of both the final mid-course correction and, if appropriate, the jettisoning of the SIM bay door. From this, FIDO calculated the definitive LOI-1 burn. All the information associated with the burn was written onto a no-carbon-required pad that allowed six copies to be made at once, with the top layer being written using a red ballpoint pen in order to help to distinguish what was to be read to the crew. 1...

Medical matters

Although the Apollo crews were drawn from a pool of very fit men, each of whom had undergone an exhaustive medical examination before being hired and again before the flight, they were nonetheless human and ended up suffering the normal range of minor illnesses and conditions during their flights that one would expect from any sample of healthy people. One perennial problem that afflicted the early flights was the common cold. It made life much harder for the Apollo 7 crew when they all...

The first staging event cutting up the ship

Rocketry theory had demonstrated early on that building a rocket using a series of modular stages would allow engineers to loft payloads into space with much greater efficiency than trying to use a single stage, at least with current technology. Therefore, the Saturn V was built as a three-stage vehicle. When each stage was exhausted, it was cut adrift to coast on alone to its fate while a fresh stage took up the task of getting the spacecraft out of Earth's atmosphere and then to the Moon. The...

Plane change manoeuvre

When the entire Apollo stack of LM and CSM arrived at the Moon, it was placed in an orbit that would pass over the landing site at the time of landing. Then once the LM had departed for the surface, the CSM returned to a 110-kilometre orbit if it wasn't already there. While the surface crew carried out their exploration, the Moon continued to rotate on its axis and, in most cases, took the landing site away from the orbital plane of the CSM. The exception was Apollo 11, for which the landing...

Liftoff Final seconds

At the very tip of the Saturn V stack, the rounded point of the launch escape tower (LET) included eight small holes which led to a device called the Q-ball. Shortly before launch, the cover was removed that had protected these holes from debris and insects. Their function was not dissimilar to the pitot tube seen on conventional aircraft for measuring airspeed, because the Q-ball measured how the air pressure across the eight holes changed as the vehicle rammed through the atmosphere during...

A bigger space

With the departure of his two crewmates to the lunar surface, the CMP had a bigger space to move in and life on board the Apollo command module became somewhat more comfortable. Michael Collins elaborated on this extra space in his autobiography. I have removed the centre couch and stored it underneath the left one, and this gives the place an entirely different aspect. It opens up a central aisle between the main instrument panel and the lower equipment bay, a pathway which allows me to zip...

P a quest for all balls

Although the IMU was finely engineered, the platform inevitably drifted very slowly out of perfect alignment with the REFSMMAT, and had to be realigned at regular intervals. Naturally, the CMP turned to the spacecraft's optical system to take sightings of the stars. Because this task was carried out in conjunction with the computer using Program 52, it was simply known as doing a P52, another ubiquitous term in Apollo jargon. If the crew needed to perform any kind of propulsive burn, which...

Aborting after LOI

Retro's second offering concerned the abort situation when the spacecraft had already entered lunar orbit. For the entire period that an Apollo spacecraft flew in orbit around the Moon, mission control ensured that the command module pilot always had the data he needed to leave lunar orbit and return to Earth, even if an extreme situation meant that he had to come home on his own following the loss of the LM. These were trans-Earth injection (TEI) burns, one of which would eventually be used in...

Counting Down To The Burn

What's the time '' asked Aldrin from Columbia's right-hand couch. The crew of Apollo 11 had made their attitude checks prior to TEI, and were checking that the engine bell was swivelling on its gimbal correctly in response to steering commands. Preparations were going smoothly and there was a light mood in the cabin as their incredible flight began to look as if it might actually come off. We have 12 minutes to go,'' replied Collins, occupying the left couch. Aldrin had been wondering what they...

The Apollo flights a brief history

Owen Maynard, one of the engineers who had been designing manned spacecraft for NASA from the beginning, reduced the task of reaching the Moon to a series of missions that, one by one, would push Apollo's capability all the way to the lunar surface. These missions were assigned letters of the alphabet A, B, C, etc. Managers believed that if the lunar goal was to be realised, each of these preliminary missions would have to be successfully flown - more than once if necessary - before the...

Communications Unified Sband and VHF

Apollo used two radio frequency ranges for communications VHF and S-band. Originally, NASA had intended to implement the radio systems that they already had available to fulfil the disparate requirements of voice, data, television, as well as the need to track the spacecraft out to the Moon. But it soon became clear that this would involve the installation of multiple items of hardware, with severe weight penalties, and so, as far as possible, the engineers strove to implement many of these...

How can you get to the Moon with just that

At the core of the G& N system was the Apollo guidance computer. Now seen as primitive in comparison to its successors, it was nevertheless one of the items in the Apollo programme that helped to drive forward important technologies in electronics and computing. It demanded compactness and low power consumption, allied with high computational power - capabilities that could only be performed by a new device that was just coming out of American research laboratories the integrated circuit or...

Inflight exercise

Although Apollo occurred in the first decade of manned space flight, doctors had already begun to test the body's reaction to weightlessness during the Gemini programme and had noticed how muscle tone and bone mass was lost after only a few days. Exercise was believed to be the key to mitigating these effects, although this was next to impossible in the cramped confines of a Gemini spacecraft, but the greater volume afforded by an Apollo cabin permitted some limited exercise, especially when...

The Route To The Moon Translunar injection

Flying to the Moon, when you don't have a lot of propellant to hose around, is like a stone throw - a ballistic lob across 400,000 kilometres of space between two worlds. The impulse for this 'throw' came from the S-IVB stage of the Saturn V which added an additional 3 kilometres per second to their speed with a burn nearly 6 minutes long. As this translunar injection TLI burn progressed, it modified the spacecraft's circular orbit into an increasingly long, stretched elliptical orbit whose...

New Knowledge Apollo

The scientific feast continued with Apollo 16, launched on 14 April 1972 to explore what were believed to be 'highland volcanics' within the rugged hills near the crater Descartes towards the centre of the Moon's disk. Its crew of John Young, Charlie Duke and Ken Mattingly nearly had to abort their mission some hours before landing, when the main engine on board the CSM Casper began to wobble when Mattingly tried to test its back up steering system preparatory to a scheduled burn. Once this...

Lunar Orbit Rendezvous

Any journey in space is heavily influenced by the propellant available to achieve it. At the same time, the amount of propellant required is largely determined by the mass of the object that is to make the journey and how quickly the journey has to be undertaken. The alternative scheme, known as lunar orbit rendezvous LOR sought to limit the amount of mass that had to be propelled at any stage of the journey. A reduction in the quantity of propellant required for the Apollo spacecraft would...

Xray fluorescence spectrometer

Having essentially no atmosphere, the Moon has little protection from the Sun's constant output of x-rays that wash over its day-lit surface and strike whatever gets in their way. When they strike certain elements, particularly those at the lighter end of the Periodic Table, they cause the atoms to re-emit or fluoresce x-rays in certain well-defined energies. Therefore, by comparing the spectral make-up of x-rays from the Sun with x-rays from the sunlit lunar surface, scientists could determine...

Heatshield sacrificial surface

Heatshield designs for Apollo originated in the re-entry vehicles that were developed in the 1950s for nuclear warheads. These weapons were launched on ballistic arcs out into space by large rockets to increase their speed and minimise delivery times, but as their elaborate mechanisms had to negotiate the great temperatures generated by reentry, they were protected inside a vehicle whose outer wall included some form of heatshield. Initially heat sinks were used, but development of this Cold...

DOI with the LM

For Apollo 10's rehearsal and for the first two landings, the CSM remained in its 110-kilometre orbit, leaving the LM to enter the descent orbit itself with a DOI burn. On Apollo 11, this was a 30-second burn, 15 seconds with 10 per cent throttle and the remainder with the throttle set to 40 per cent. Having a period of time at a low thrust setting allowed the gimbal mechanism, on which the descent engine was mounted, to align the engine's thrust with the spacecraft's centre-of-gravity. This...

Looking out of the window

Responsibilities in the LM were tightly defined, especially during the approach and final phase. The commander wanted to keep his eyes out of the window, watching where the spacecraft was going. The LMP, on the other hand, generally had to keep his attention inside the cabin. His responsibility was to vocally feed whatever relevant information the commander would require at a given point in the descent. The details of this were worked out by each crew individually over the months of training...

Transposition Docking And Extraction Preparations

The first step in the whole process was to ensure that the command module's cabin was pressurised with air up to its maximum extent, about two-fifths of an atmosphere. This was in preparation for later when, to save the LM's scarce resources, its initial air supply would be drawn from the CM cabin air. Valves on each side of a tunnel that would eventually connect the two spacecraft would then allow air to be exchanged between them. While the crew worked through the TD amp E checklist, the APS...

Freereturn

Free Return Trajectory

Even before Kennedy's challenge, the lunar free-return trajectory had been recognised as a safe and efficient means by which a spacecraft could make the journey. This was a wonderful solution to the problem, one whose propellant needs were within the capabilities of the Saturn V, that could get a crew to the Moon within three days and allow the entire mission to be carried out within 14 days, well within the duration for which the Apollo spacecraft was being designed. Furthermore, if something...

Cleanliness

Just as there was no conventional toilet, the spacecraft contained no shower or basin. On a flight lasting less than two weeks, simpler regime. Washing was performed by just having a wipe with one of the available cleansing cloths. Two types were available wet and dry each about 10 by 10 centimetres, with the wet cloths containing a germicide. These were specifically intended for general cleansing after food and defecation. Afterwards, the skin was dried with tissues from one of seven...

Dead band

The next stage of the LM checks required the crew to think about the concept of the dead band, which is another of those curious terms in spaceflight where a simple concept lay behind opaque jargon. Apollo was one of the first applications of a digital fly-by-wire system whereby control of a vehicle was placed in the hands of a computer. In the Apollo guidance computer, programmers included a series of algorithms that would fire the RCS jets as necessary to bring the spacecraft to a desired...

Redundancy in control

The designers of the Apollo spacecraft were always careful to build redundancy into their systems to ensure that a single point failure could not jeopardise the crew - a philosophy that extended to the guidance and navigation system. The designers were very aware that any of its exotic components could fail at any point in the mission. To this end, the command module had a second control system which, although it shared many components with the G amp N system, could operate entirely separately....

Entry monitor system

The crew's next task was to put the entry monitor system EMS through a series of tests to verify that it could be trusted in its role, which was, as the name implied, to monitor the progress of the re-entry. This bit of kit on the main display console came into its own in the final minutes of the mission, but its weight wasn't carried for 2 weeks without it having to work for its passage. NASA's engineers saved weight by having systems share their components where possible, so throughout the...

Mascons a lumpy Moon

Over a one-year period between 1966 and 1967, five Lunar Orbiter spacecraft were dispatched to the Moon to carry out comprehensive photo-reconnaissance of its surface, largely in support of the Apollo programme. It was mostly through this programme that engineers gained the skills necessary to accurately track an object around the Moon and control its flight path. Controllers were surprised to discover that, unlike orbits around Earth where the gravity field is nearly uniform, the orbits of...

Rendezvous Techniques

Once NASA had accepted LOR as the Apollo mission mode, they had to work out how rendezvous, whether in Earth or in lunar orbit, should be accomplished. The problem is far from straightforward, and the solution did not spring forth from the mind of some brilliant engineer. Rather, it evolved from 1964 right through to the first landing and continued to evolve throughout the programme. The problems were many. Some of the major factors with which they had to contend were how accurately would the...

Braking And Stationkeeping

The final major manoeuvre of the rendezvous was braking. Since the TPI burn, the LM had been coasting on an intercept trajectory that was essentially part of an orbit. The apolune of that orbit was a kilometre or more higher than the altitude of the CSM and, without braking, the LM would have sailed by in front of its target. Starting from a distance of nearly 3 kilometres, the commander executed a series of manoeuvres to reduce the closing speed of the two spacecraft. Each was pre-planned to...

Third Stage The second staging event

It was only when the S-II tanks had run dry and a signal had been sent to shut down its engines, that the Saturn's computer could begin the next stage of the ascent - the staging event that discarded the spent S-II and ignited the S-IVB for the first of its two burns. The same signal began Timebase 4 in the instrument unit to choreograph everything that had to occur. Unlike the dual-plane separation between the first and second stages, this cut was made across a single plane at the top of the...

Final preparations

Over the final few hours before entering lunar orbit, the Apollo crews began an exhaustive series of checks and adjustments, interrogating their spacecraft's systems about their ability to sustain life while in the Moon's clutches, and on the engine's readiness to do its job properly. Another important task in the build-up to LOI was to change the spacecraft's knowledge of which way was 'up'. During the 5 or 6 minutes of the burn, the crew wanted to avoid any appreciable errors in the direction...

How Apollo Flew to the Moon

Editor - Apollo Flight Journal NASA web resource SPRINGER-PRAXIS BOOKS IN SPACE EXPLORATION SUBJECT ADVISORY EDITOR John Mason B.Sc., M.Sc., Ph.D. ISBN 978-0-387-71675-6 Springer Berlin Heidelberg New York Springer is a part of Springer Science Business Media springer.com Library of Congress Control Number 2007932412 Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication...

Door jettison

The final three Moon-bound Apollo missions, Apollos 15 to 17, had one special task to perform prior to arrival in lunar orbit. Sector 1 of their service modules contained a scientific instrument module, or SIM bay for short. It housed a variety of cameras and instruments to investigate the Moon and its environment, and would be operated by the CMP during his lonely vigil while his crewmates explored the lunar surface. Hidden as it was behind the external skin of the service module, the SIM bay...

Walk Outside

On the day after TEI, the command module pilot of the J-missions took centre stage. The cameras of the SIM bay had photographed their images onto long lengths of photographic film stored in large circular magazines, which were now sitting in the service module, itself to be discarded in a few days time when it would burn up and be destroyed in Earth's atmosphere. The film therefore had to be brought into the command module's cabin, the only part of the spacecraft that would survive reentry. To...

Subsatellite

In an effort to get around the terribly short period of time that an Apollo CSM orbited the Moon, barely a week at most, scientists added a small, 35.6-kilogram subsatellite to the SIM bays of Apollos 15 and 16. This was ejected just before the crew headed home. Its function was to investigate the various particles and fields in the lunar environment. 'Particles and fields' is an expression used within the planetary science community for the investigation of planets and their environments...

Getting the height right

The spacecraft's design had assumed that the windows would face forward during the final approach to give the crew a view of their landing site, and that it would pitch into this attitude from a windows-up attitude. If the windows were facing up, and given that the landing radar had to face downwards, then its antenna had to be mounted on the base of the descent stage on the side opposite the windows. Intrepid, Houston,'' called Carr to Conrad and Bean. You're looking good at three minutes .''...

The circularisation manoeuvre

In all instances, the two spacecraft were allowed to separate once the LM was well into the checkout of its systems and no problems were being encountered. For the later missions, Apollo 14 onwards, mission control read up a PAD with which the CMP could make his circularisation burn. In truth, the orbit resulting from this burn was not really circular but was made deliberately elliptical. This reflected the fact that FIDO was compensating for the perturbation of the CSM's trajectory by the...

Program alarms part II

Apollo 11 had already had a brief encounter with the computer throwing out program alarms during the braking phase. As Armstrong and Aldrin brought Eagle through the approach phase, the computer began to play up again. Eagle, Houston. You're Go for landing,'' said Duke in the Capcom chair. Roger. Understand. Go for landing. 3,000 feet,'' returned Aldrin, as they passed 1,000 metres altitude. Just then, Aldrin made a call that the computer was acting up yet again. Program alarm. 1201.'' 1201,...

LM abort modes

In the continuing spirit of NASA's defence-in-depth philosophy, a series of PADs were read up to the crew that not only told them exactly when they were going to start their descent to the surface, but also what to do in the event of an abort being necessary at various times before, during and after the descent - in case the radio link were to fail. As the flights progressed, these PADs increased in complexity as planners learned from previous missions and made their procedures more elaborate....

Landing site Refsmmat

The landing site REFSMMAT was another of the many frames of reference used during an Apollo flight. It was carefully chosen to aid a landing crew by having their attitude displays, the FDAIs, or 8-ball, give readings that made sense to a pilot approaching the lunar surface. This frame of reference was defined as being the attitude of the landing site with respect to the stars at the predicted time of landing. The actual orientation of the landing site, of course, continuously changed as the...

Ptc Spacecraft On A Spit

Space is a strange place for those of us who are used to the warmth of Earth. Here on our planet, the air around us, the oceans and the land absorb the heat from the Sun and, as a result, temperatures are moderated. We know instinctively the importance of air in the transportation of heat, whether it is between the sea and land, within the rooms of our houses or inside the equipment we possess. In space, things are very different. Imagine placing an object in cislunar space, not too near the...

Transearth Injection

The NASA-ese term for the manoeuvre that brought the spacecraft out of lunar orbit and homeward to Earth was trans-Earth injection TEI . In simple terms, it was very similar to the TLI manoeuvre that sent the crew moonward in the first place in that its task was to add more speed to the spacecraft in order to raise the high point of its orbit sufficiently to take it from one world to another. To achieve this, their orbital velocity had to be raised by nearly 1 kilometre per second. With only...

Saturns guidance

At T-20 seconds, swing arm 2 was retracted from its position connected to the top of the S-IC. As it arced back to the tower, the guidance system on the Saturn was finally set for the flight. In the instrument unit above the S-IVB stage, there was a conventional gimbal-mounted guidance platform - the type that can hold its orientation while the vehicle around it rotates. As the Earth turned with the Saturn V on the pad, the platform kept its alignment with respect to the stars. If an onlooker...

Landing point designator

In the LPD, the computer's programmers had devised a simple but powerful way to tell the commander where P64 was taking them. It was as simple a device as you could hope to find in a high-tech spacecraft, though its operation depended on what was then one of the world's most sophisticated small computers. It consisted of nothing more than lines carefully scribed onto the inner and outer panes of the commander's forward-facing window that marked his line of sight, measured from a line directly...

Long

For their pioneering journey to the surface of the Moon, Armstrong and Aldrin made only a single foray onto the surface before attempting to get some sleep in the uncomfortable confines of the LM. The rendezvous and docking next day were therefore carried out by a crew that were hopefully rested to some extent. As each successive flight became more ambitious and the LM was trusted with a crew for longer periods, the rendezvous and docking day grew increasingly packed. At first, 4-hour, and...

Crossing the equigravisphere

Between the Moon and Earth, there came a point where the gravity of the approaching body became stronger than that of the receding body. When this point of gravitational equality was reached, it was customary for mission control, and especially those concerned with flight dynamics, to switch their frame of reference from one world to another. However, because the Moon itself was in motion around Earth, the numbers representing the spacecraft's speed and position appeared to jump. Journalists...

The launch escape system

Apollo Escape Tower

When the spacecraft was sitting on top of the Saturn V, it included one extra element of the Apollo system that everyone hoped would never be used. If it had, it would have been a particularly bad day for all involved. Attached to the tip of the CM was a truss structure upon which was mounted a thin, pencil-like tower which included a Computer rendering of the LM ascent stage. Image courtesy of Scott Sullivan. Computer rendering of the LM ascent stage. Image courtesy of Scott Sullivan. Diagram...

The Apollo lander

Apollo Leg Fold

The CSM was a streamlined and sturdy craft, designed to ascend through the atmosphere of Earth, and, in the case of the command module, withstand a punishing re-entry. In complete contrast, the lunar lander was a true spacecraft because it was entirely incapable of flight in an atmosphere. Known as the lunar module LM , its construction was entrusted to the Grumman Aircraft Engineering Corporation. This was a truly exotic ship in which every aspect of its major systems pushed the know-how of...

The Apollo spacecraft

Apollo Command Module Cutaway

The command module was a stubby, conical craft almost entirely covered with a heatshield that was thickest across its base to sustain most of the punishment of re-entry. The outer rim of the cone was packed with small tanks, thrusters, various antennae and two small ports for the ejection of waste water and urine. The apex of the cone had a removable probe mechanism to enable it to dock with the Apollo lander and a tunnel through which the crew could transfer between the two spacecraft....

Command module RCS

Having heated the command module's thrusters, the rest of its reaction control system could be primed, ready for use. Throughout the mission, all small-scale manoeuvres were carried out using the RCS thrusters on the service module. The command module's RCS was a simpler system primarily because there was no need to perform translation manoeuvres. It controlled the command module as re-entry began, presenting it to the atmosphere in its naturally stable, aft-first attitude until aerodynamic...

Entering lunar orbit the LOI manoeuvre

On the journey to the Moon, two events symbolised the crew's daring and acceptance of risk more than any other. One was the landing itself, which committed two crewmen to an utterly inhospitable lunar surface unless a small rocket engine worked properly to get them off and begin their journey home to Earth. The other was lunar orbit insertion LOI , the point in the journey when Apollo crews committed themselves to the gravity of the Moon. After LOI, there was no possibility of a return to Earth...

The restaurant at the edge of the universe

Longest Neck Ring

One of the cliches that has become firmly set in the public's mind since the space age began 50 years ago is that space food is a bland, dehydrated mush that comes in a tube. Certainly, for the earliest flights, this was true. However, on Apollo, things began to change a little. Some of the food taken on Apollo was dehydrated, for good reason. Water makes up a substantial component of soups and juices, and makes them heavy. Since spare water was plentiful anyway as a by-product of the fuel...

Probe and drogue spacecraft sex

Apollo Docking Mechanism

The docking system was one of the many engineering wonders of the Apollo programme and one whose importance is perhaps underplayed. The docking system was an ingenious, compact, pneumatic and mechanical arrangement that managed to elegantly fulfil an enormous range of tasks it self-centred the two spacecraft as they contacted it absorbed the shock of that contact to achieve a soft-dock and, finally, it pulled the two craft together to achieve hard dock and straightened their axes as it did so....

The midcourse correction

The purpose of determining the state vector was to see if their course to the Moon was true and, if not, to do something about it. With this in mind, seven occasions were set aside in the flight plan for possible trajectory corrections four on the way out and three for the return trip. Having determined the state vector and calculated the current trajectory, FIDO -the controller primarily concerned with planning the spacecraft's trajectory - then brought the RTCC computers to bear on the task...

LOS and AOS out of sight

Apollo missions were intensively monitored from Earth. Because they had deep technical visibility into the spacecraft's systems through telemetry, and huge computing and personnel resources on hand in case of problems, mission control became accustomed to nursing its crews and machines over the days of the coast to the Moon. It was then a bit of a wrench when some of the most critical events in an Apollo flight, particularly the entry into and departure from lunar orbit, had to occur with a...

Lunar whiskers

Dave Scott Apollo

Many lunar explorers returned to Earth with two weeks' growth proudly displayed as they stepped off the helicopter following their recovery. Others chose to shave even though it could be difficult. Mike Collins did a bit of both, returning to Earth with a decent moustache. Although these normally fastidious men tolerated such limitations to their personal hygiene for the duration of a mission, many began to be irritated by them towards the end and were only too glad to get...

Power the fuel cell

Apollo Oxygen Tank Exploding

Buried within the pie-shaped structure of the service module were originally two later three tanks each of oxygen and hydrogen. Although these two substances are excellent propellants for rocket engines, propulsion was not their purpose in the Apollo design. A common notion is that spacecraft usually derive their electrical power from the Sun via large arrays of solar cells. While this is generally true for automatic spacecraft in the inner solar system and for the international space station,...

The state vector

In order to describe a flight path in space, the trajectory experts simply need to know two things where the spacecraft is and how fast it is going at any particular time in the flight. But before they can express these two concepts they must have some frame of reference against which to measure them. If I were throwing a stone across my back garden and wished to define its path -assuming I had access to the necessary measuring equipment - I might be able to state that 1 second into its flight,...

Undocking

To begin the process of splitting the two spacecraft, the electrical umbilical that connected them was disconnected within the tunnel, and the probe and drogue docking mechanism put back in place. Two other umbilicals were reconnected to the docking equipment to pass telemetry and commands to and from the probe and to supply power to fire its retraction mechanism. The LM hatch was installed by the LM crew as the CMP put on his helmet and gloves, a safety measure for the next task of preloading...

Coelliptic rendezvous the orbital ballet

To control the approach speed of the LM, NASA standardised how it would fly the final part of the rendezvous - what it termed the terminal phase. Theoretical studies and Gemini experience demonstrated that the best approach was to fly this terminal phase over the time that the CSM had travelled 130 degrees of its orbit, with approach speeds set out for every stage of this arc to allow the crew to keep control of the situation. Therefore, planners could choose where in the CSM's orbit they...

Tindallgrams

The manner in which the team decided how to deal with this low-level quantity warning light taps into one of Apollo's most interesting side stories, because it illustrates the management style of Howard Wilson Bill Tindall, one of the senior engineers. He was an expert on the subtleties of rendezvous and trajectories and became head of the Mission Planning and Analysis Division. In the hectic days leading up to Apollo's successes, he coordinated the planning process that threaded together the...

FHH a moment to look towards his collea

., . gue standing in the hatch Jim, you f ' '''r B look absolutely fantastic against that . . . i JjSB Moon back there. That is really a jy. iH most unbelievable, remarkable thing. Worden had no camera with him to record this unique interplanetary view, but after they returned to Earth, artist Pierre Mion carefully reproduced the scene in a painting. When Worden had finished off by making an examination of the SIM bay on Houston's behalf, he and Irwin got back into the cabin, taking the camera...

Gimbal lock

Missile Gimbal Apolo

After Neil Armstrong and Buzz Aldrin had landed their LM Eagle on the Moon and while they were preparing for their foray onto the surface, Mike Collins made strenuous efforts to locate the tiny LM among the monotonous wastes of craters on Mare Tranquillitatis by aiming his sextant where mission control reckoned they were. Getting the optics around to face the surface and back again involved carrying out a number of manoeuvres. It was during the manoeuvres after one such viewing opportunity that...

Apollo an extraordinary adventure

The Apollo programme was not just a Cold War stunt, though many correctly saw it as such. Neither was it just an example of superpower posturing, though it most certainly was that too. As is the nature of so many decisions in the human realm, America's decision to go to the Moon in the middle of the twentieth century had repercussions that were barely imagined when the President's advisers steered him towards his historic decision. In a speech on 25 May 1961, to a Joint Session of Congress on...

A crewmans favourite sight red and white

With only 3,000 metres remaining, another barometric switch operated, firing mortars that deployed three pilot chutes into the smooth air stream. These pulled the three main parachutes out from their bays around the tunnel, which slowed the spacecraft's descent to just 8.5 metres per second. The three main chutes were a welcome sight to the crews and became familiar to the public as the impressive 25-metre red-and-white canopies that featured clearly on the television coverage of an Apollo's...

The entry PAD a worked example

The figure for pitch reflected the expected attitude the spacecraft would naturally adopt with its biased centre-of-gravity in their current heads-down attitude. The next two items were related to the first of many checks of their attitude and trajectory. This check would be made at 290 hours 06 minutes 32 seconds into the mission, 17 minutes prior to hitting the atmosphere. It did not require any fancy instruments. All that was required was for the crewman...

Cosmic tape measure

The second ground-based tracking system determined the range or distance to the spacecraft by measuring delay. Most people are familiar with the annoying delay introduced into television interviews carried out over satellite links. It takes light, and therefore radio about one and a quarter seconds to travel from the Moon to Earth, so the return travel time for a signal to a spacecraft at the Moon is about two and a half seconds. Engineers used this delay to measure range by putting a marker...

Definitions entry interface and the event

To aid their calculation of the spacecraft's entry trajectory, mission planners adopted an arbitrary height of 400,000 feet or 121.92 kilometres, at which the returning command module was deemed to have left space and begun re-entry. This was entry interface. The Retro flight controller's task was to shape their approach trajectory to ensure that when they reached this altitude, the flight path would form an angle to the horizontal of 6.5 degrees, with a leeway of about 1 degree to help to cope...

Navigating to the Moon

There is a poetic beauty to the Apollo flights which lies in the fact that the crews navigated between worlds by sighting on the very same stars their ancestors would have employed to guide boats and ships across the oceans of Earth. The maritime connection even extended to the instrument used for the task, because the Apollo spacecraft had its own sophisticated version of the sextant, an optical device used for centuries by sailors to measure angles between stars, the Sun and Earth's horizon....

Task Accomplished Apollo

Michael Collins Suiting For Apollo

Apollo 11 departed the Kennedy Space Center in the early morning of 16 July 1969 on a mission to attempt to land on the lunar surface. It is widely quoted that over a million people gathered in the vicinity of Cape Canaveral to witness what promised to be an event of epic historic import. For the first four days, its crew of Neil Armstrong as commander, lunar module pilot Edwin 'Buzz' Aldrin and the command module pilot Michael Collins successfully followed a path already trod by their...