At 8:13 p.m. EST a 217-second S-IVB auxiliary propulsion system burn aimed the S-IVB for a lunar target point so accurately that another burn was not required. The S-IVB/IU impacted the lunar surface at 8:10 p.m. EST on April 14 at a speed of 259 meters per second. Impact was 137.1 kilometers from the Apollo 12 seismometer. The seismic signal generated by the impact lasted 3 hours 20 minutes and was so strong that a ground command was necessary to reduce seismometer gain and keep the recording on the scale. The suprathermal ion detector experiment, also deployed by the Apollo 12 crew, recorded a jump in the number of ions from zero at the time of impact up to 2,500 shortly thereafter and then back to a zero count. Scientists theorized that ionization had been produced by 6,300 K to 10,300 K (6,000 degrees C to 10,000 degrees C) temperature generated by the impact or that particles had reached an altitude of 60 kilometers from the lunar surface and had been ionized by sunlight.

Meanwhile back in the CSM/LM, the crew had been performing the routine housekeeping duties associated with the period of the translunar coast. At 30:40 ground elapsed time a midcourse correction maneuver took the spacecraft off a free-return trajectory in order to control the arrival time at the moon. Ensuring proper lighting conditions at the landing site. The maneuver placed the spacecraft on the desired trajectory, on which the closest approach to the moon would be 114.9 kilometers.

At 10:08 p.m. EST April 13, the crew reported an undervoltage alarm on the CSM main bus B, rapid loss of pressure in SM oxygen tank No. 2, and dropping current in fuel cells 1 and 3 to a zero reading. The loss of oxygen and primary power in the service module required an immediate abort of the mission. The astronauts powered up the LM, powered down the CSM, and used the LM systems for power and life support. The first maneuver following the abort decision was made with the descent propulsion system to place the spacecraft back in a free-return trajectory around the moon. After the spacecraft swung around the moon, another maneuver reduced the coast time back to earth and moved the landing point from the Indian Ocean to the South Pacific. References: 2, 6, 16, 26, 27, 33,60.

On the morning of April 24, 1970, the first and second stages of CZ-1 were loaded with propellant and stacked. The satellite was mated to the spin-stabilized solid-propellant third stage, and the launcher entered the final eight hours of launch preparation. Weather forecast for the launch at 9:30 p.m. called for clouds at above 7,000 meters and a wind speed of less than 4 to 5 meters per second.

The historic launch came at 9:35 p.m. local time (13:35 UTC). Upon hearing the command "ignition", a launch controller pressed the button to start the rocket engines. The three-stage CZ-1, which was 29.46 meters tall and had a maximum diameter of 2.25 meters, lifted off the launch pad with a thrust of 104 tonnes. Liftoff weight of the CZ-1 was 81.5 tonnes. Rocket expert Shen Jianan recounted that "..as soon as I saw the liftoff on the TV screen inside the bunker, I ran outside. I could only see the beautiful rocket lighting up the night sky and streaking towards the southeast. I ran back inside to listen to the transmissions. Broadcasting on the speaker were status reports like 'capturing target', 'nominal tracking', 'nominal flight', 'nominal second and third stage separation'..." Thirteen minutes after launch, at 9:48 p.m., mission control announced "...satellite and rocket stage separation, satellite enters orbit...the bunker was filled with cheers".

China became the fifth nation after the former Soviet Union, the United States, France and Japan to achieve an indigenous space launch capability. At 9:50 p.m., the National Broadcasting Bureau announced the acquisition of the tune 'East is Red' from the satellite loud and clear. In the following days, the People's Central Broadcasting radio and newspapers in Beijing announced and printed worldwide times of DFH-1 and CZ-1 third stage passages, and directions of travel in the sky. Senior officials in Beijing dispatched a chartered plane to JSLC to bring back Qi and other scientists. In the International Labour Day celebration on May 1, Chairman Mao and Premier Zhou warmly welcomed them at the Tiananmen Square. References: 2, 6.

• The common orbiter/booster engine planned would have to have a lower thrust then proposed, with more used per booster. This was due to the need for the orbiter to have several engines instead of one or two in order to give it abort capabilities in the event of a single engine failure. It was recommended that a 180,000 kgf engine be developed for the shuttle instead of the 230,000 kgf previously planned.
• Lifting body configurations were not suited for the launch vehicle application. This was due to the required complex internal arrangement of tanks and equipment within the curving hull, difficulty of fabricating the airframe and tanks, and poor subsonic lift/drag performance.
• Variable geometry wings were not desirable, since they resulted in a heavier weight to body area ratio during re-entry, and thereby more re-entry heating problems. They also required complex mechanical and pneumatic/hydraulic systems for operation, which meant more maintenance, more complexity, and extra failure modes. There considerable advantages - a lower spacecraft weight fraction and the highest lift/drag in subsonic flight - did not offset these disadvantages.

• Two-stage-to-orbit, vertical takeoff, horizontal landing configuration
• Initial operational capability by the end of 1977
• 6,800 kg payload to a 500 km, 55 deg inclination orbit when launched from Cape Canaveral
• 4.6 m x 18.3 m payload bay
• Two orbiter alternates were to be proposed by the contractors, one with a 370 km cross-range (NASA requirement), one with a 2784 km cross range (USAF requirement). This implied a minimum L/D for the high cross-range vehicle of 1.8, and a total heat load 5 to 7 times greater than the low cross-range alternative.
• Seven-day orbital mission capability.
• Go-around capability on landing in case of a missed approach. This implied the use of airbreathing engines. Phase A studies showed that use of gaseous H2 from the orbiter's tanks as fuel for such engines drastically reduced the orbiter weight compared to use of conventional JP-4 jet fuel housed in separate tanks.
• Design to be capable of 25 to 70 launches a year, with a turnaround time of two weeks
• G-forces limited to 3G on ascent
• Two crew housed in a pressure cabin without spacesuits
• 43 hour countdown time after assembly
• Stage separation without the use of rocket devices
• No in-flight refuelling allowed
• Capable of landing under FAA Category 2 conditions on a 3,000 m runway
• All systems fail-operational - e.g. they would remain operational after any single component failure, and remain fail-safe for crew survival even after two subsystem failures
• Quick safeing of vehicle systems after landing
• No propellant cross-feed allowed between booster and orbiter

The Mathematica study would become notorious, for it forecast enormous savings in the use of the shuttle. It became very influential in government and congressional circles in shifting opinion to support the project. This, as NASA Administrator Low would dryly comment later, was 'unfortunate'. All earlier studies for the USAF and NASA, notably a RAND study in 1970, showed no cost advantage for reusable boosters when research and development costs were taken into account. RAND had concluded that a manned space station supported by expendable boosters would be cheaper, and more flexible and useful.

Fletcher also directed NASA to take US Air Force requirements for the shuttle into account. The US Defence Department's requirements included the ability to carry 18 m long payloads, and deliver a mass of 18,000 kg to a polar orbit from Vandenberg AFB, or 30,000 kg to a low earth orbit from Cape Canaveral. The 4.5 m diameter for the payload bay was a NASA requirement, established by the planned diameter of future space station modules. 18 m x 4.5 m also corresponded to the dimensions of a liquid hydrogen tank with a mass of 30,000 kg, the lowest-density payload imaginable. The USAF also wanted an 1800 to 2400 km cross range on re-entry, and an initial operational capability of December 1977.

The Aerospace Corporation study of NASA Phase A proposals concluded that the weight of a shuttle's thermal protection system would vary in relation to the fourth root of the required cross range. Aerospace also believed that sequential ignition of the booster and orbiter was a better approach than the triamese-type all-engines running at lift-off. It also declared that the USAF's desired operational date was unrealistic -- the earliest a shuttle could be available was mid to late 1979. References: 44.

In the evening Kamanin calls Tereshkova, and promises to tell Nikolayev that she and Aleuka were fine, worried, to kiss him, and the looked forward to meeting him on his return. On 8 June Aleuka will be six years old, and Tereshkova would like to fly to Yevpatoriya to give her a surprise communications session with her father. At 21:25 Kamanin relays the news from his family to Nikolayev during a pass over Yevpatoriya. Kamanin observes that the tracking station is not suited to serve as mission control over a long spaceflight. There is no transport, and no recreational facilities. The only diversions are gymnastics, chess, and billiards. Furthermore there seem to be a lot of unnecessary staff at the command point. References: 376.