Category How Apollo Flew to the Moon

The decision to control the Saturn V from its own instrument unit instead of using the capabilities of the command module’s guidance system was primarily driven by the expectation that the vehicle would one day be called upon to carry payloads
other than the Apollo spacecraft. It was dramatically shown to be a fortuitous decision when the Apollo 12 stack was struck by lightning only 36 seconds after it lifted into overcast cloud on 14 November 1969. Although the nearest natural lightning was many kilometres away, the exhaust of the rocket left a trail of ionised gas that acted like a giant conductor and enabled the cloud’s static charge to reach the ground.

"What the hell was that?” called Dick Gordon after the interior of the cabin was flooded by a flash of white light. Gordon, the CMP for this mission, and his commander Pete Conrad were carefully watch­ing the main display console. "I lost a whole bunch of stuff,” yelled Gordon. Directly in front of him, the caution and warning panel “was a sight to behold” as Conrad would later recount.

Sixteen seconds later, another strike hit the vehicle during a cloud-to-cloud discharge. “Okay, we just lost the platform, gang. I don’t know what happened here; we had everything in the world drop out.” Conrad continued to inform them that the fuel cells that powered the spacecraft were no longer doing so, and that the guidance platform in the command module had tumbled out of alignment. The platform was now useless as a tool to guide anything, never mind the giant rocket that was currently powering them to space. Below them, the Saturn V had been entirely unaffected by the electrical catastrophe that had befallen its payload and it continued its programmed ascent without missing a beat. The crew rode their Saturn on into orbit, where they were able to bring the spacecraft’s power back on line, align their guidance platform and continue successfully to the Moon.

Pete Conrad was one of the most colourful characters among the astronauts and was never short of a quip. “I think we need to do a little more all-weather testing. That’s one of the better sims, believe me,” he joked, comparing this real-life drama to the many simulated dramas they had practised endlessly prior to the mission. Capcom at that time, Gerry Carr, wasn’t short of a line of his own, “We’ve had a couple of cardiac arrests down here, too, Pete,” to which Apollo 12’s commander replied, “There wasn’t any time for that up here.”

Later in the mission, Conrad laughed about the experience. “The launch was almost as good as me getting to fly the Saturn V into orbit.” His was only the second Saturn equipped to allow the commander to fly manually to orbit – a contingency
that, while never called upon, would have been welcomed by the hot-shot commanders within the astronaut corps.

Gordon continued the quips as he spoke with Carr. “That’s a terrible way to break A1 Bean into space flight, I’ll tell you.”

At this stage, having achieved an orbit, it is worth considering what a spacecraft does to change it. Our box of beads has no means of propulsion and once released into its orbit, it is doomed to revolve around our imaginary Earth to the end of time. Of course, real life isn’t like that. Spacecraft usually have some kind of rocket motor, especially human-carrying ships that must return to the home planet.

Imagine, then, that our box of beads is a spacecraft w’ith an engine. Let us assume that, having entered a circular orbit, we want to reach a higher orbit. To do so. we must increase our speed further by firing the engine, its nozzle aimed rearwards. This would straighten out the flight path a little and cause the spacecraft to enter an elliptical orbit in which it would coast to an apogee on the other side of the planet. The point at which the burn w’as made becomes a perigee, and if the duration of the burn is appropriately timed, the spacecraft can be made to ascend to any desired apogee altitude. Half an orbit later, having slowed down considerably (just like any object tossed upward in a gravity field), it arrives at apogee but does not have enough momentum to stay at that altitude and will fall back to its perigee as it continues around the planet. Apogee then becomes a good place to adjust the altitude of the orbit’s perigee. By adding yet more speed at apogee with another burn, the flight path is straightened out further, so that the spacecraft does not fall

quite so far as it descends to perigee. If enough extra speed is applied at apogee, the shape of the orbit can be made circular again, this time at the higher altitude. This method of transferring from one orbit to another involving a pair of burns perfonned 180 degrees apart is known as the Hohmann transfer orbit and was formulated in the early part of the twentieth century by Walter Hohmann, a member of the same German rocketry club as Wernher von Braun.

Now comes the counter-intuitive bit. Although our imaginary spacecraft’s speed had been increased on two occasions, it ended up travelling much more slowly than when it was in the lower orbit. Its speed had been traded for height, a situation that will be familiar to all fighter pilots. There are all sorts of ramifications to this in terms of spaceflight operations, especially for Apollo. For example, if one spacecraft wanted to catch up with another that was ahead in the same orbit, the wrong thing to do would be to aim towards the target, light the rockets and try to fly directly towards the quarry. This would make its orbit more elliptical, raise it to a higher apogee and it would therefore travel more slowly, thereby opening the range, which is exactly the opposite of the desired effect. The right thing to do would be to turn the craft around and fire to slow down, thereby making the orbit elliptical with a lower perigee. This increases the spacecraft’s speed and closes the range. Then, to effect a rendezvous the spacecraft would need to turn around yet again and make another burn to rise back up to the target’s orbit at just the right time.

Clearly, making large manoeuvres in space has to be done with careful forethought. Computers and radars are also indispensable tools. This was especially true during an Apollo flight where the success of the mission depended on the ability of two spacecraft to rendezvous successfully. It was also true from the point of view

of their next major manoeuvre; the burn to set them on a path to the Moon, itself essentially a Hohmann transfer.

Immediately after the Apollo/Saturn stack had achieved orbit, Earth-based radars began to track the vehicle to determine its trajectory as precisely as they could. From these measurements, computers at mission control calculated a suitable Moon – bound trajectory and the details of a burn that would achieve it. given the constraints of what the S-IVB could manage. These details were transmitted to the computer within the instrument unit. Whatever information was relevant to the crew was passed on to them also in the form of a list of numbers manually read up by the Capcom. Based on these calculations, and after a little more than 2’/2 hours orbiting Earth, the S-IVB stage reignited and set the Apollo spacecraft on its path to the Moon.

The final stage of the TD&E process was the ejection of the lunar module from the S – IVB, which was not simply a process of throwing a switch and then watching it happen. Throwing the switch would come at the end, but first they had to feed the signal from the switch in the CM down past the LM to the pyrotechnically-fired spring thrusters on the SLA that would push the LM free. That meant that the CMP had to connect two umbilical cables to feed power and signals between the two spacecraft. However, to do that he had to get into the tunnel, which is a short void between the command module’s forward hatch and the lunar module’s overhead hatch. Immediately after the docking, the space within the tunnel was still a vacuum so the CMP had therefore to bleed oxygen from the CM into the void and, in doing so, he also fed it into the LM cabin. Prior to launch, the dump valve in the LM’s overhead hatch was left open in order that, as the Saturn V lofted both spacecraft to orbit, the mixed atmosphere within the LM was gradually exhausted, leaving the interior essentially a vacuum, ready to be filled with oxygen. By docking with the LM, the tunnel had been placed over the hatch and its dump valve. Once the pressure on both sides of the forward hatch had equalised, the hatch itself could be removed, the umbilicals could be connected to feed power to the pyrotechnic devices for freeing the LM, and a check could be made to ensure that all twelve latches had properly engaged. Finally, the switch could be thrown to eject the LM from the S – IVB and allow the Apollo stack to continue its journey to the Moon.

None of these steps were simple, as each had its own checklist of items that had to be set or verified to ensure that the crew did not configure the spacecraft in a way that might endanger their lives. The process was carried out in a slow, methodical fashion of checks, verification and cross-checks: forty minutes work to allow them finally to throw one switch.

A catalogue of 37 stars distributed across the sky was programmed into the rope memory of the onboard computer. There w’ere some quite faint stars in the list, but this w’as only because the brightest stars are unevenly distributed across the sky. Planners had w’anted to ensure that irrespective of the direction in which the fixed line of sight of the optics was pointed, the crew7 would find a star sufficiently bright within the range of the movable line of sight to view through the sextant. Haeh star had a numerical code in base eight (octal) so that the crewman could tell the computer which star he wished to use. or in other cases the computer w’ould indicate the star that it had chosen for a specific operation.

Some of the objects in the Apollo star list were not stars at all. Three numbers were set aside so that the Sun. Moon and Harth could be referenced by the crewman for other tasks, and there w’as also a code that allowed a ‘planet’ to be defined if needed. In fact this could be any celestial object and in some cases, this ’planet’ was actually a star, just not one that the computer knew about.

Three of the fainter stars in this list have unconventional names that were added as a practical joke by the crew of the ill-fated Apollo 1 during their training. Star 03,

Navi, is the middle name of Gus Grissom (Ivan) spelled backwards. Likewise, his two crewmates added oblique references to themselves among the Apollo star list: Star 17, Regor, is the first name of Roger Chaffee spelled backwards; and Edward White II gave his generational suffix to the prank by spelling ‘second’ backwards as Dnoces and applying it to Star 20. The people of Apollo kept these names in their literature as a mark of respect to a fallen crew and they have been known to appear in a few star atlases and books in succeeding years.

Soon after the crew of Apollo 8 had begun their coast to the Moon, they removed their suits and never put them back on for the rest of the flight. After all, there were no plans for a spacewalk or any undocking event to pose a risk to the integrity of the cabin’s pressure hull. After the flight, Frank Borman wondered whether they had been required at all. “I would not have hesitated to launch on Apollo 8 without pressure suits,” he said at the debriefing after the mission. He continued, "We wore them for about three hours and stowed them for 141 hours. I see no reason to include the pressure suits on a spacecraft that’s been through an altitude chamber.” However, suits were needed for the ascent to allow the crew to breathe pure oxygen, and for the whole flight in case the spacecraft’s hull was breached for some reason.

All subsequent flights did require the crews to suit up regularly, either for operational reasons (a walk on the Moon is an obvious example) or as a precaution when pyrotechnic charges were cutting pieces from the spacecraft. For example, the final jettison of the lunar module required an explosive cord to cut through the

tunnel wall just in front of the forward hatch.

In some ways, a spacesuit can be seen as the ultimate in extreme out­door gear. Just as a climber on the peak of Mount Everest has to dress up appropriately, an Apollo astro­naut had to protect himself from the conditions he was about to encoun­ter. Like the mountaineer, he had a supply of oxygen as well as protec­tion from the cold and the heat in the rays of the Sun. Two distinct types of suit were produced for Apollo. The CMP had a simpler suit while the surface crews’ suits were designed to support a back pack that allowed them to work on the lunar surface. The following refers to the surface suit.

Air to breathe was fed into the suit either from the back pack, called the

portable life support system (PLSS,

pronounced ‘pliss’), or from the spacecraft via hoses. A fine network of water-filled tubes worn next to the skin kept control of the suit’s internal temperature as the crewman worked. The main part of the suit had an airtight bladder with layers of Dacron fibre, Mylar foil and woven Teflon cloth to protect against heat and cold. The outermost of the suit’s 18 layers was white Teflon cloth that helped to protect against abrasion.

Instead of sunglasses or goggles, a polycarbonate helmet was worn over the head that allowed almost all-round vision. An additional cover, which was worn over the helmet, included a visor that was thinly plated with gold to reflect light and infra-red radiation. It also had a set of pull-down shades at the top and to each side that the crewman could deploy to protect his eyes from the intense lunar sunlight.

When inflated to a pressure of 250 millibars, the suits ballooned and stiffened, which made them difficult to bend and hold in a set position. To counter this, flexible joints were built into various parts of the suit and a network of cables within the layers allowed a posture to be adopted and held. The gloves contained thermal insulation and the fingertips were made from silicone rubber to help to improve the astronaut’s sense of touch. On Apollo 15, David Scott arranged to have his fingertips up against the end of his gloves with the result that, over the course of his 18 hours on the surface, his bruised fingernails had begun to lift from his fingers.

The PLSS carried batteries to power the pumps and communications gear, high – pressure oxygen for breathing, a lithium hydroxide canister for removing carbon dioxide from the suit’s air, and a supply of water for cooling. The cooling element was a clever piece of kit called a sublimator. Water was fed through a porous metal plate where, on reaching a vacuum, it evaporated, thereby removing heat to form ice. From that point on, the ice would continue to sublimate to space and take heat with it as long as more water was fed to replace the lost ice. This cooled the separate water circuit that went around the crewman’s skin.

By the end of a J-mission’s lunar stay, a crewman’s suit was a heavily abused item of clothing that had undergone 20 hours of intense work in the hostile environment of the Moon. Often a crewman would accidentally fall and cover himself in dirt, or the guards over the w’heels of the rover would break off and the crew would be sprayed with dust as they drove. The suit’s outer layer was therefore heavily ingrained with dirt and its locking rings around the neck and wrists w ould threaten to seize owing to the highly abrasive nature of the all-pervasive lunar dust. These multimillion-dollar wonders of engineering are now museum fodder.

After they woke up on the final day of their coast to the Moon, a crew would set about their usual post-sleep chores of reporting their condition to mission control and preparing their breakfast. Normally the spacecraft w’as slowly turning around in its barbecue roll, spreading the heat of the Sun across its surface. While the crew slept, engineers at the ground stations on Earth had taken precise measurements of the spacecraft’s position and velocity to accurately monitor its trajectory. Using this data, FIDO, the flight dynamics flight controller in the MOCR, calculated the amount by which the approach to the Moon needed to be adjusted, if at all. Was the spacecraft coming in too quickly or Loo slowly to pass around the far side at the correct altitude? Was it within the correct orbital plane to pass over the desired landscape? Based on the results of overnight radio tracking, and with the help of the big computers in the real-time computer complex (RTCC), FIDO calculated the details of a burn to be carried out at the fourth opportunity for a mid-course correction, usually scheduled to occur five hours prior to entry into lunar orbit. The details of this corrective burn w’ere read up to the crew1, along with the results of calculations by the Retro flight controller.

While FIDO had been deciding w’here they wanted the spacecraft to fly. Retro was busily working out what to do if something w’ent w’rong. He had Lw’o scenarios to consider: the first was if something were to prevent or impair the LOI burn; and the second was for the situation in w’hich the LOI burn w’as completed successfully but the crew7 were required Lo return Lo Earth at the earliest opportunity. Having decided the manoeuvres that the crew’ should make in these scenarios, it was then important that the details be passed up to the spacecraft while it w’as still in communication with Earth. The mantra was that they should always have the data necessary to get home without further assistance from mission control, in case communications w’ere lost.

In the years after World War II. in the bowels of America’s aeronautical research facilities, a few remarkably gifted engineers were having ideas above their station. Thinking outside the box. as we now call it, they wondered how a manned spacecraft (women were never considered) that had been blasted outside Earth’s atmosphere, could possibly return without killing its crew. Two in particular, Max Fagct and Owen Maynard, were formulating a plan to bring together diverse technologies that were then maturing which might allow the dream of space travel to be realised. Many of these technologies were also concerned with the delivery of nuclear weaponry – the most prominent examples being the liquid-fuelled rocket, the ablative heatshield and the blunt-body re-entry vehicle.

Both the USA and the Soviet Union had been familiarising themselves with rocket technology gleaned from the defeated Germans of World War II. Having learned from rocket engineers who had worked for the Nazis, both superpowers had launched vehicles that had been either looted from central Europe or built locally on the basis of German experience. It soon became apparent that these rockets would be useful carriers for the newly developed nuclear warhead, able to dispatch these weapons across large distances in a short time. Both sides in the Cold War had nuclear armaments, and both realised that in the event of an exchange, early delivery of their warheads would be crucial to national survival.

Fast delivery of nuclear weapons required development of the intercontinental ballistic missile (ICBM) whose long, coasting flight could cross continents in half an hour. Though this class of missile was not required to go fast enough for orbital flight, much of its trajectory was spent in the vacuum of space and one of the chief problems encountered in this arrangement was dealing with the punishing heat the payload had to endure as it re-entered the atmosphere at hypersonic speeds.

After dispensing with solutions that tried to absorb the energy in a heat sink, engineers turned to the ablative heatshield. This was a layer of material on the outside of the warhead fabricated from materials that would ablate – that is, they would slowly char and burn away, carrying the heat and thereby protecting the bomb as it came hurtling back into the atmosphere. At the same time, the work of H. Julian Allen had shown that by forming the shape of a re-entering body into a blunt shield, the searing hot shockwave that always accompanied high-speed aerody­namics could be made to stand away from the fabric of the hull, and thus keep the hottest and most erosive gases clear of the vehicle.

Faget and Maynard investigated whether this technology could be arranged so that a person could sit inside the rocket’s payload instead of a warhead, enter space and return to Earth without being roasted, chilled, asphyxiated, crushed or drowned. An early implementation of their work was the one-man Mercury spacecraft, a relatively unsophisticated capsule that enabled America to log its first minutes and hours of manned space flight. Even before the first such flight was attempted, engineers had begun to consider the design of a successor that could sustain a three-

man crew for an extended flight in space and make a controlled descent through the atmosphere to land on the ocean. Although there was no specific mission for such a spacecraft, the engineers were intrigued by the possibility that it might be able to fly to the Moon.

The name for this spacecraft, Apollo, was coined in mid-1960 by the Director of NASA’s Office of Space Flight Programs, Abe Silverstein, who delved into Greek mythology for inspiration. Apollo was the son of Zeus and had associations with Helios the Sun god. In Silverstein’s mind, the idea of Apollo riding across the face of the Sun seemed an appropriate metaphor for the grand sweep of the programme that such a spacecraft might be able to undertake.

In May 1961, America had hardly dipped its toe in space with the 15-minute flight of Alan Shepard, when President Kennedy proclaimed a mission for this nascent spacecraft by challenging his nation to send a man to the Moon and return him safely to his home planet, and to do so within the eight and a half years still remaining of the 1960s. Kennedy’s early months as President had been troubled by a succession of ‘space firsts’ achieved by the Soviet Union, particularly on 12 April 1961 when Yuri Gagarin became the first person to fly in space by making a single orbit of Earth. Further trouble with an aborted invasion of Soviet-backed Cuba made Kennedy seek something that would raise America’s profile around the world. Landing men on the Moon, a goal that people within NASA were already thinking about, and carrying it out to a deadline, seemed like an enterprise at which his country could excel. The Apollo system would be pressed into this role.

As soon as the world learned of Sputnik’s launch, it was clear that the United States lagged behind the Soviet Union in the lifting capacity of their launch vehicles. But this was no failing of their designers. Rather, most rocket research to this point had been in support of both nations’ nuclear weapons programmes and because US designers were better at building smaller, lighter weapons their rockets were smaller. The Atlas missile used for the Mercury orbital flights and the Titan for the Gemini programme were really delivery systems for nuclear weapons, and struggled to lift their manned payloads. It became habitual for designers to minimise payload weight as they strove to maximise the capability of their spacecraft within the constraints of the available rockets. One decision to save weight would have tragic consequences for what was to have been the first manned Apollo mission.

On Earth, the atmosphere consists of four-fifths nitrogen and one fifth oxygen, the latter being the gas that sustains life. To save the substantial mass of the
equipment required to supply two gases in a manned spacecraft, NASA decided that the cabins of its space­craft would be filled with 100 per cent oxygen, but at a low pressure to ensure that the crew received only the concentration of oxygen mole­cules to which their lungs were accustomed. This single-gas arrange­ment worked well throughout the Mercury and Gemini programmes, and was a sound engineering deci­sion, but as the first Apollo crew were preparing their spacecraft for flight, this nearly ended the pro­gramme.

On 27 January 1967, the AS-204 mission was three weeks away from its planned launch. It was so desig­nated because it was to use the fourth vehicle in the Saturn IB series.

Informally, it was dubbed Apollo 1.

The Apollo spacecraft, CSM number 012, was a Block I type and was sitting on top of an unfuelled launch vehicle. Its crew of three were strapped in for a ‘plugs out’ countdown simulation in which the ability of the entire space vehicle to function on its own power would be tested. The cabin had been deliberately overpressurised with pure oxygen in order to test for leaks, as had been done in ground tests for the Mercury and Gemini programmes. Five and a half hours into a simulated countdown that had made only halting progress, a fire began near the commander’s feet. In the super-oxygenated environment, this quickly grew into an intense conflagration that ruptured the hull of the spacecraft and asphyxiated the three crewmen – Gus Grissom, Ed White and Roger Chaffee.

NASA sustained heavy criticism from the press and the political classes for this tragedy. Some was directed at the manufacturer, North American Aviation, with accusations of sloppy workmanship. North American rebutted, pointing out that as it tried to build the spacecraft, NASA had insisted on interfering with the process by ordering a multitude of changes. In congressional hearings on the fire, astronaut Frank Borman appealed for support from the lawmakers. “We are confident in our management, our engineering and ourselves. I think the question is: are you confident in us?”

NASA learned many lessons from this accident and applied them to the rest of the Apollo programme. Some commentators have argued, convincingly, that there was a very real possibility that, had the fire not occurred, NASA would never have realised

its lunar dream. They point out that the shock of the deaths spurred all those involved in the programme, especially at NASA and North American, to make the Block II spacecraft into the great spacefaring ship it became. Without the changes imposed by the tragedy, casualties may have occurred later in the programme, possibly in space. At the very least, the development problems of the Block I Apollo spacecraft would probably have crippled the programme at a later stage had they not been brought into sharp focus so early on.

Although NASA wanted to keep this unflown mission’s name as AS-204, it acceded to the widows’ requests that the name Apollo 1 be reserved for their dead husbands’ flight. Crews had been in training for Apollos 2 and 3, scheduled for later in 1967, but they were cancelled.

Meanwhile, a few months after the Apollo fire the Soviet Union grieved at its first loss of a cosmonaut during a test of the new Soyuz spacecraft. Both nations therefore had to cope with setbacks in their race to the Moon.

PREPARATIONS FOR LAUNCH Leaving the VAB

Final preparations for the launch of an Apollo mission began weeks in advance in one of the cavernous aisles of the 160-metre-tall vehicle assembly building (VAB). On a large steel platform, 49 by 40 metres, a complete but unfuelled Apollo/Saturn space vehicle, itself 110 metres tall, was stacked. ‘Space vehicle’ was a term for a combined launch vehicle and spacecraft. It started its journey when a 2,700-tonne diesel- powered crawler/transporter that employed tracked tractor units derived from heavy open-cast mining equipment jacked itself up underneath the platform and carried the combined load of 5,700 tonnes out through one of the massive doors and along a 5 V2 – kilometre crawlerway to one of two launch complexes, 39A or 39B, from which the rocket would make its fiery departure.

The crawler/transporter was one element of a mobile launch system that had been devised by members of Wernher von Braun’s rocket team. They had suggested that for a vehicle as large as an Apollo/Saturn V, the task of stacking its stages and installing the Apollo spacecraft on top would be best carried out inside a large hangar. The resulting VAB was a huge box-shaped building 52 storeys tall at the focus of Kennedy Space Center (KSC). In a sense, it was from here that a journey to the Moon began.

If the space vehicle had to be stacked indoors, a method had to be devised to get it out to the launch pad. Barges within dedicated canals were considered, as were great layouts of railway tracks, before the mobile launcher concept was decided. This called for a platform upon which the space vehicle would be fixed until the moment of launch. A tower even taller than the rocket sprouted from one end of the platform, which took the height of the whole affair to 136 metres. This launch umbilical tower (LUT) supplied the space vehicle with its essential services by way of nine huge arms that reached across from the tower. These tended the vehicle until they were swung away either prior to launch, or in some cases disconnecting and

W. D. Woods, How Apollo Flew to the Moon, Springer Praxis Books,

DOI 10.1007/978-1-4419-7179-1 3. © Springer Science+Business Media. LLC 2011

pulling away only as the rocket began its flight. Though they weighed an average of 22 tonnes, these arms could quickly accelerate away from a rising rocket, and just as quickly brake to a halt close against the tower.

With the VAB doors open, the crawler/transporter lifted the platform clear of six supporting pillars and carted the entire assemblage away at about 1.5 kilometres per hour. To accommodate the pressure of the crawler’s 456 treads, each weighing nearly a tonne, a specialised roadway had to be constructed wherever it needed to go. A metre depth of support ballast fonned a bed for a layer of aggregate that bore the immense weight of the crawler and its load as they were steered along their journey to the launch pads.

After 42 seconds of flight, the rules of what would happen in case of an abort changed slightly to take account of the fact that the space vehicle had tilted over substantially and had also gained plenty of horizontal speed. The mission had moved into abort mode one-bravo which lasted until it reached an altitude of 30.5 kilometres. If an abort were to be called during this period, the escaping command module would no longer be in danger of falling into the Saturn’s debris, and the small motor intended to steer it out to sea would no longer be required. What was needed, however, was a way to ensure that the CM would turn to face the correct direction after being pulled from an aborting Saturn. This was because tests had shown that at hypersonic speeds, it was possible for the CM/escape tower combination to be stable in a nose-first attitude. The tower could not be safely jettisoned in this mode because the airflow would ram the boost protective cover onto the CM hull, which would not only prevent the tower pulling away but would also prevent the deployment of the parachutes.

Once the LES had pulled an aborting spacecraft free, two skin sections near the top of the tower, known as canards, would deploy after the escape motor had done its job. The drag they created would thereby force a turn-around manoeuvre, if one were needed, to face the heatshield in the direction of travel, and enable the tower to be jettisoned cleanly and the parachutes to be safely deployed.