The Manned Spacecraft Center allocated spacecraft Nos. 16 and 19 for the six-orbit mission, with No. 16 as the preferred vehicle. No. 16 had arrived at Cape Canaveral in January 1962, while No. 19 had followed two months later. Rework to incorporate a six-orbit capability was done at the Cape by the MSC Preflight Operations Division with the help of McDonnell technicians. The work and testing began slowly but were well underway in April. In that month temperature surveys at the critical points on the capsule were completed, the environmental control system passed its altitude-chamber tests, and the reaction control system was exercised satisfactorily. Minor troubles cropped up, as usual. Emergency oxygen rate valves stuck. Water coolant flowed too freely. The cabin's oxygen leakage rate was too high. Each difficulty slowly was overcome, but it became evident that a hoped-for August launching might slip at least a month.7
The Mercury Project Office had pronounced 5.4 pounds of lithium hydroxide sufficient for oxygen purification for the MA-8 mission, but the MSC Life Systems Division personnel checking this theory found the absorbers unsatisfactory. Canisters containing 4.6 pounds of the mixture had been used in the three-orbit spacecraft and tests showed that this amount of the chemical functioned to keep the air breathable for 34.5 hours before carbon-dioxide levels rose too high. Then canisters supposedly containing 5.4 pounds of absorbent were tested, with both fixed and variable inputs of heat, water vapor, and carbon dioxide, and with a human subject breathing the oxygen. To the amazement of the testers, the lifetimes of these canisters averaged only slightly higher than those that were partly filled.
Then it occurred to somebody in the division to weigh the canisters. Each proved to have been packed about half a pound short. Finally the completely filled canisters were tested for as long as 71 hours before breaking down, demonstrating that the original design met the development demands, after all. Well filled absorbers would qualify for a day-long mission as well as for six orbits.8
As the work continued at the Cape on spacecraft No. 16, Scott Carpenter made his fuel-thirsty, three-orbit flight on May 24. During Aurora 7's postflight analysis MSC engineers, including G. Merritt Preston's checkout crew, took new and closer looks at the attitude and reaction control systems. They decided that attitude thrusters slightly different in design would have to be installed in the MA-8 spacecraft. While Preston's men were implementing this decision, they also managed to get No. 16's cabin oxygen leakage rate down to a highly satisfactory 460 cubic centimeters per minute, although in the weeks ahead this rate would rise slightly.9
Other results from MA-7, as recorded from telemetry data, as reported by Carpenter, and as revealed by examination of flight-tested Aurora 7, had intensified the flurry of activity all along the line to prepare No. 16 for its flight. Carpenter had many suggestions regarding spacecraft configuration. The heavy periscope, he said, was useless on Earth's nightside; the window alone could be used to find the spacecraft's attitude. The determined workers for spacecraft weight  reduction were delighted to hear this assessment. But the MA-7 postflight inspection team reported that Carpenter's landing error had been caused by a faulty yaw attitude, largely because Carpenter had performed a final control systems check just prior to retrofire and had used the window mainly as his chief yaw reference. Could the window and the pilot be trusted? the Mercury team wondered. Would the periscope have assisted in correcting the attitude and the resultant overshoot? The only way to find out the answers was to fly the periscope again.10
So for MA-8 the periscope became, in a sense, an experimental instrument. Using both the periscope and the window for spacecraft attitude reference, Schirra would check the position of his capsule carefully on Earth's day and night sides. Then he would check his visual judgment to gauge attitude, comparing his ability against the scope and instrument readings.
Having decided to retain the periscope, the mission planners and Cape preparations team for MA-8 butted into fresh difficulties. The experiment schedule had called for an ultraviolet airglow spectrograph to be put in the periscope's well. This spectrograph had been developed through the intensive work of Albert Boggess, III, at the Goddard Space Flight Center upon the request of the NASA Headquarters Ad Hoc Committee on Scientific Tasks and Training for Man-in-Space. Now the decision to carry the periscope forced the withdrawal of the experiment, creating some disappointment among NASA's scientifically interested personnel. Even the implementation of this decision turned out to be somewhat of a problem. Preston's men tried to use the periscope from the alternate spacecraft (No. 19) but found it to be defective. By the end of August they managed to install a standard periscope, "cannibalized" from spacecraft No. 15.11
Carpenter, the second astronaut to land with empty fuel tanks in the manned orbital program, also suggested that a control-mode selector switch be integrated with the control system to seal off the high thrusters until they were needed for fast reaction maneuvers. The Project Office approved, and this fuel-saving switch was installed in the MA-8 spacecraft.12
Aside from these and other minor modifications spacecraft No. 16 was a duplicate of Aurora 7. Many of the technical changes were aimed at weight reduction, fuel conservation, and adding extra supplies for a longer mission. Deletions included the astronaut-observer camera, one of two redundant command receiver-decoders, and the high-frequency voice transceiver. To increase pilot comfort and save weight, the preflight preparations crew extracted the lower leg section of the couch and substituted toe, heel, and knee restraints. During the orbital phase of the mission, the knee restraints could be loosened. An extra 15 pounds of coolant water and an improved fastening technique for the heatshield center plug completed the list of additions.13
While the engineers were working, Astronaut Schirra proceeded through the most efficient flight training program yet undertaken. Except for added yaw recognition displays, he used the same procedures trainers that his predecessors had used;  having a definite flight plan, he could practice on his own specific mission profile. He was able to work through his simulated retrofire and reentry tasks in the Langley procedures trainer before the device was dismantled for shipment to Houston. And for personal physical conditioning, he often went swimming and water skiing.14
Late in July, Preston reported that the work schedule for spacecraft No. 16 was aimed at a September 18 launch date. When the flight preparation crews added a sixth day to their work week to compensate for various delays, the MSC managers remained optimistic.15
Some worry among the mission planners had been injected in July when Project Dominic, an Atomic Energy Commission (AEC) high-atmosphere nuclear test over the Pacific, had created a new zone of radiation, lower than the Van Allen belts. In the face of this possible threat to an orbiting man, AEC, NASA, and McDonnell carefully studied a number of satellite and probe launchings in August designed to explore the belt. After the solar batteries of several satellites failed - including Ariel I, the world's first international satellite project, which developed operational difficulties probably attributable to Dominic - the investigators reported that the new radiation circled Earth at the geomagnetic equator and was about 400 miles wide and 4000 miles deep. Sounding rockets by telemetry data indicated rapid and continuing decay of radioactivity in the corridors of the next Mercury mission. By the end of August the radiation hazards seemed negligible. The MSC engineers, distrusting the reports that all danger had disappeared, installed a radiation dosimeter on the spacecraft hatch, provided the pilot with a hand-held model, and attached four more to Schirra's pressure suit.16 The hand-held model could provide real-time indications during the flight.
Besides some labor-management difficulties that momentarily hampered the activities of the aerospace industry at this time, the booster for MA-8 contributed its share of troubles. Atlas 113-D was to have been delivered to Cape Canaveral toward the end of July, but it failed its initial composite test at the San Diego factory. Finally it was shipped on August 8. Then the Air Force, revealing that its Atlas program had suffered four recent turbopump failures, advised the Manned Spacecraft Center that No. 113-D would be put through a flight-readiness static firing. Since the MA-8 launch vehicle would be the first one in the Mercury program not having the two-second post-ignition hold-down time, the Air Force felt the static firing to be an important requirement.
A one-week slippage was now added. But before the test could be made, the Air Force and Convair inspectors found a fuel leak in a seam weld on the booster. Calculating the time required for work to be done, on September 6 the Mercury–Atlas launch operations committee rescheduled the mechanical and electrical matings of spacecraft and booster and three planned simulated flights. These tests would continue through September 24, making October 3 the most likely day for the MA-8 launch.
 Atlas 113-D actually differed little from its predecessors in the manned flight program. It incorporated a dozen or so technical changes from the 107-D configuration that had propelled Carpenter into orbit. The fuel tank insulation had been removed as a solution to some of the difficulties that had beset John Glenn's booster (Carpenter's launch vehicle had retained the insulation). More important, baffled fuel injectors (which had been found in static firing tests to virtually eliminate the possibility of combustion instability) and the accompanying hyperbolic ignition (in which fuel and oxidizer ignite on contact) were added to 113-D. These innovations, therefore, eliminated the two-second hold-down at ignition, saved fuel, made for smoother initial combustion, and provided a safer liftoff.17
The tracking network for MA-8 was augmented by five airborne relay stations, in the form of five Air Force C-130s, to cover areas that otherwise would have been out of communications range of the ground sites. The C-130s, each equipped with ultra-high-frequency and very-high-frequency equipment for voice relay, were based at Patrick Air Force Base, Florida; Ramey Air Force Base, Puerto Rico; and Midway Island.18 The mixed recovery force, deployed by the Department of Defense, included 19 ships in the Atlantic and nine in the Pacific. Aircraft numbering 134 of various types covered primary and secondary spacecraft landing areas. In all, about 17,000 men, including over 100 aeromedical monitors and specialists, made up the global MA-8 recovery forces.
Recovery commanders in the Pacific directed a training course in spacecraft and astronaut retrieval for appropriate teams, using boilerplate capsules, flotation collars, and other gear provided by MSC. Major General Leighton I. Davis and Walter C. Williams made an inspection tour to the Pacific to evaluate the training program and the overall recovery readiness picture. Later Kraft, reading their findings, reported that preparations and materials seemed "reasonably well" developed. But he was disappointed that NASA had been unable to enlist the support of another Navy radar ship equipped with FPS-16 equipment for C-band operation and thus had to rely on two S-band ships instead. Kraft felt that S-band radar, called "Verlort" for its 700-mile "very long range tracking" ability, was less reliable than the C-band.19
If recovery was to go smoothly, interservice misunderstandings like the one that had developed during Carpenter's rescue would have to be avoided. General Davis, the DOD military representative for Mercury support operations, had reported to Secretary of Defense Robert S. McNamara that the delay at Mercury Control in the decision to pick up Carpenter had stemmed partially from a lack of direct communication with the astronaut. To overcome this breakdown, the recovery room in the Control Center was modified to permit almost instantaneous communication between tracking stations and recovery forces; and Schirra's spacecraft was equipped with a long extension line, which would permit him to maintain voice contact even in the life raft. The extended period of suspense that climaxed Carpenter's mission should never happen again in Project Mercury.20
 At this juncture, President Kennedy set out on a tour of the space centers of the South to inspect and show his interest not only in the preparations for MA-8 but also in the vast array of technological talents being mobilized for the accelerated space program, including the first lunar voyage. Kennedy flew down to Cape Canaveral to see the Merritt Island Launch Area that was being built for the huge Saturn V rockets. Then he went on to Houston to see the site for the management and control center on the Texas coastal prairie. Before a sweltering crowd half-filling the 72,000-seat Rice University stadium, the President spoke on September 12, 1962, in earnest defense of his proclaimed program for manned exploration of the Moon. "No man can fully grasp how far and how fast we have come," said Kennedy. "The exploration of space will go ahead, whether we join it or not. . . . It is one of the great adventures of all time, and no nation which expects to be the leader of other nations can expect to stay behind in the race for space. . . . We intend to be first. . . . to become the world's leading space-faring nation." The youthful President then addressed one of his memorable statements to those who had asked, "Why send a man to the Moon?"
We set sail on this new sea because there is new knowledge to be gained and new rights to be won, and they must be won and used for the progress of all people. For space science, like nuclear science and all technology, has no conscience of its own. Whether it will become a force for good or ill depends on us, and only if the United States occupies a position of preeminence can we help decide whether this new ocean will be a sea of peace or a new, terrifying theater of war. . . . Space can be explored and mastered without feeding the fires of war, without repeating the mistake that man has made in extending his writ around this globe of ours.21If President Kennedy's remarks in Houston, later at the McDonnell factory in St. Louis, and elsewhere, proved an accurate reflection of most Americans' sentiments about the space program, his words persuaded few of the vocal economic, political, and scientific conservatives who were watching costs soar along with the engineering effort. The NASA space budget alone for this fiscal year was over $5 billion, which represented a tax of about 40 cents on each American per week; but the Nation was prosperous, the economy seemed sound, and critics of the "space circus" were seldom heard.
Toward the end of September, all mission preparations, the astronaut, the spacecraft, and the launch vehicle reached a high state of readiness. The spacecraft and the booster mated well; the simulated tests before mission ticked off without further hitches; and October 3 thus remained a promising launch date.
Schirra, viewing the elaborate preparation effort, studying his flight plan, and knowing that his mission involved the evaluation of the capsule's ability to accomplish a day-long flight, recognized the immensity of the engineering effort behind him. In honor of these labors, he selected the name Sigma 7 for his spacecraft. "Since this was to be an engineering evaluation," he explained, the name chosen for capsule No. 16 was that of an engineering symbol for summation, Sigma,  with the number seven added to it for the seven-member Mercury astronaut team. "Thus," he said, "was derived the name and symbol that was painted on the spacecraft, Sigma 7."22
On the final lap toward launch day, Schirra began a controlled diet on September 21; nine days later physician Howard A. Minners placed him on his low-residue diet. Schirra complained mildly while adjusting to the low-residue food, but in every other respect he was primed and ready, mentally and physically.
As always when flight day neared, the Mercury operations team through the Weather Bureau support group kept a watchful eye on existing weather disturbances in both the Atlantic and Pacific areas. About 400 miles north by northeast of Puerto Rico, tropical storm Daisy churned the waters of the Atlantic, while three typhoons, Dinah, Emma, and Frieda, whipped Pacific waves. On October 1, Walter Williams told the news corps covering the flight at the Cape that except for the weather "all elements of the MA-8 flight are in a go condition as of this time." By 5 p.m. the following day, Williams was satisfied with the chances for success and decided to launch as planned.23
Notified by Williams that he had a 7 o'clock liftoff "appointment" the next morning, Schirra dined leisurely and retired early. Without any sleep-inducing medications, the pilot drifted into slumber shortly after 8 p.m. and got about five hours of sound rest. Minners roused Schirra at 1:40 a.m. to begin the precise readiness routine. The astronaut showered, shaved, and met with Gilruth, Williams, Slayton, and Minners for breakfast. He ate heartily the "astronaut launching breakfast,"  consisting of eggs, filet, dry toast, orange juice, and coffee, plus a portion of a bluefish that he had speared the day before. The major preflight physical having taken place two days earlier, Minners checked Schirra briefly, pronouncing him in excellent physical condition. After Minners applied the physiological sensors to the astronaut's body, Schirra signaled to Joe W. Schmitt to assist him in donning the silvery pressure suit. At a little past 4 o'clock, Schirra and his attending retinue emerged from Hangar S.
As Schirra headed for the transfer van, Alvin B. Webb, a veteran space-newsman assigned by the press pool to report activities in that area, observed that the astronaut seemed to be unusually relaxed and smiling, as compared to previous astronauts on their way to the launch pad. Seconds later, Schirra, carrying his portable air conditioner, climbed aboard the van for a leisurely ride toward the flood-lit spire in the distance. As the van reached the blockhouse and gantry complex, Byron G. MacNabb, representing the Convair-Atlas team, greeted Schirra and said: "On behalf of the crew of Pad 14, I wish you a successful flight and a happy landing." Acknowledging this salutation, Schirra boarded the elevator and moved up the gantry. At 4:41 a.m. the astronaut slid inside Sigma 7.24
7 Ms., George F. Killmer, Jr., et al., "Mercury Technical History - Preflight Operations," MSC Florida Operations, Dec. 30, 1963, Chart 126; "Weekly Activities Report," Mercury Project Office, April 20, 1962; "Weekly Activities Report," Mercury Project Office, April 13, 1962; "Project Mercury Quarterly Status Report No. 14 for the Period Ending April 30, 1962," NASA/MSC, May 25, 1962; "Weekly Activity Report to the Office of the Director for Manned Space Flight," MSC, May 5, 1962; memo, G. Merritt Preston to Dir., MSC, "Monthly Activities Report No. 6," April 26, 1962.
8 Memo, James P. Henry to Asst. Dir. for Research and Development, MSC, "Weekly Activity Report for the Life Systems Division," April 20, 1962; "Monthly Activities Report," Life Systems Div., April 30, 1962; memo, Richard S. Johnston to Asst. Dir. for Research and Development, MSC, "Weekly Activities Report," June 15, 1962; memo, Edward L. Hays to Asst. Dir. for Research and Development, "Weekly Activity Report," May 18, 1962; "Activities Report to the Office of the Director for Manned Space Flight," MSC, May 19, 1962.
9 "Activity Report to the Office of the Director for Manned Space Flight," MSC, May 12, 1962; "Activity Report to Director for Manned Space Flight," MSC, June 2, 1962.
10 Robert T. Everline, interview, Houston, April 15, 1965; "Minutes of the Senior Staff Meeting," MSC, Aug. 3, 1962.
11 "Weekly Activities Report for the Director of Manned Space Flight," MSC, Aug. 11, 1962; "Weekly Activities Report for the Director of Manned Space Flight," MSC, Sept. 1, 1962; Kenneth J. Vogel, interview, Houston, May 6, 1965; Fred T. Pearce, interview, Houston, Feb. 12, 1964.
12 "Postlaunch Memorandum Report for Mercury-Atlas No. 7 (MA-7)," NASA/MSC, June 15, 1962; "Postlaunch Memorandum Report for Mercury-Atlas No. 8 (MA-8)."
13 Ibid.; "Project Mercury Quarterly Status Report No. 15 for Period Ending July 31, 1962," NASA/MSC.
14 "Postlaunch Memorandum Report for MA-8," Part I.
15 "Minutes of the Senior Staff Meeting," MSC, July 13, 20, Aug. 3, 1962.
16 Astronautical and Aeronautical Events of 1962, 158; "Project Mercury Quarterly Status Report No. 16 for Period Ending October 31, 1962," NASA/MSC;"Minutes of the Senior Staff Meeting," MSC, Aug. 31, 1962.
17 "Activity Report," MSC Preflight Operations Div., July 27, 1962; James M. Grimwood, Project Mercury: A Chronology, NASA SP4001 (Washington, 1963), 214;"Minutes of the Senior Staff Meeting," MSC, Aug. 17, 1962;"Project Mercury Minutes of Meeting of Mercury Atlas Launch Operations Committee," NASA/MSC, Sept. 6, 1962;"Minutes of the Senior Staff Meeting," MSC, Sept. 28, 1962. J. F. Wambolt on July 26, 1962, prepared a "Missile 113-D History" that provides excellent details on the steps taken to man-rate a missile into a Mercury launch vehicle.
18 Letter, Maj. Gen. Leighton I. Davis, Hq., Air Force Missile Test Center, to Secretary of Defense Robert S. McNamara, "Status of DOD Support of Project Mercury for July 1962," with enclosure, Aug. 13, 1962; memo, North to Management Analysis Div.,"Weekly Activity Report, Flight Crew Operations Division," July 2, 1962.
19 DOD Representative for Project Mercury Support Operations, Final Report to the Secretary of Defense on Department of Defense Support of Project Mercury: For the Period 1 July 1959 through 13 June 1963, approved by Leighton I. Davis, Maj. Gen., USAF, 11 Sept. 1963, 15, 28;"Status Report No. 15";"Status Report No. 16"; memo, Christopher C. Kraft, Jr. [to Management Analysis Div.],"Activities Report, Flight Operations Division," Aug. 27, 1962;"Minutes of the Senior Staff Meeting," July 27 and Aug. 10, 1962; Department of Defense press kit for MA-8.
20 Final Report to the Secretary of Defense, 28; letter, Davis to McNamara,"Postlaunch Memorandum Report for MA-8."
21 Text, "Address by President John F. Kennedy," Rice University Stadium, Sept. 12, 1962.
22 "Astronaut's Flight Report," in "Postlaunch Memorandum Report for MA-8," Part I, 7—49.
23 Robert Young, "Squalls Give Schirra Orbit 50-50 Chance," Chicago Tribune, Oct. 2, 1962;"Schirra Ready for Countdown," Washington Post, Oct. 3, 1962; NASA News Release,"MA-8 Advisory," 5 p.m., Oct. 2, 1962.
24 "Postlaunch Memorandum Report for MA-8," Part I; Alvin B. Webb, United Press International, "Hangar S Pool Copy," Oct. 3, 1962. Also see "High Dreams for a Man and His Son," Life, LII (June 8, 1962).