First American in orbit
50th anniversary of first US manned orbital space flight
On 20 February 2012, NASA celebrated the 50th anniversary of the first manned orbital mission of the United States, launched from the Kennedy Space Centre in Florida.
In 1962, John Glenn piloted the Mercury-Atlas 6 'Friendship 7' spacecraft and completed a three-orbit mission around the earth, reaching a maximum altitude of approximately 260 kilometres and an orbital velocity of approximately 28 000 kilometres per hour. The mission, which landed near the Turks and Caicos Islands, lasted 4 hours, 55 minutes, and 23 seconds.
NASA engineers were faced with the challenge of devising a vehicle that would protect the astronaut from temperature extremes, the effect of vacuum and space radiation. There was the need to keep the pilot cool during the burning, high-speed re-entry through the atmosphere.
The spacecraft was cone-shaped with a cylinder on top. It was 2 metres long, 2 metres in diameter, and had a 5.8-metre escape tower with a solid-rocket motor fastened to the cylinder. In a launch emergency, the rocket would fire, lift the capsule and parachute it into the ocean. With a volume of only 12 cubic metres, there was barely enough room for its pilot, who sat in a custom-designed couch facing a panel with 120 controls, 55 electrical switches, 30 fuses, and 35 mechanical levers. The cabin's atmospheric pressure was one-third of that on Earth and the cabin contained pure oxygen.
Among the electrical and electronic systems that made this first manned orbital flight possible were navigation and control instruments as well as autopilot, rate stabilization and control and fly-by-wire (FBW) systems.
The blunt end of the capsule, which would enter the atmosphere first, was covered with an ablative heat shield to protect it from the 1649˚ C heat of re-entry into the atmosphere. This shield would burn off and dissipate the heat during re-entry and descent. Just before the spacecraft’s impact with Earth, the heat shield would detach from the base of the capsule and release a balloon that would inflate to cushion the landing. Parachutes would further slow the descent.
Problems on board
Glenn encountered some problems during his flight. First, a yaw attitude control jet became clogged, forcing the pilot to abandon the automatic control system for the manual-electrical fly-by-wire and manual-mechanical systems instead of the automatic control system
Second, a reading from the sensor monitoring the spacecraft's heat shield and landing impact bag indicated that the impact bag had deployed. This could only happen if the heat shield had come loose. If this were the case, Glenn might be incinerated during re-entry.
Mission Control felt that the reading was most likely caused by a faulty sensor on the spacecraft, and that Glenn's heat shield was fine, but they couldn't be sure. After discussing the issue, they advised Glenn not to jettison his retro pack before re-entry. If the heat shield were loose, keeping the pack attached might hold it in place.
This strategy was risky. As the retro pack itself burned up, pieces could fly off and damage the spacecraft. The heat of reentry might also cause any fuel remaining in the rockets to explode. As is the case with all space flights, there would be a temporary radio blackout during re-entry, caused by ionization of the atmosphere. Mission Control would not know if Glenn had survived until the radio blackout was over.
However, the telemetry data had been wrong. Glenn's heat shield was firmly attached, and Friendship 7 safely splashed down in the Atlantic Ocean, about 1 300 kilometres southeast of Bermuda.
IEC standardization work for electronics and avionics
Given the timing, it's likely that the electronic systems that equipped the Mercury-Atlas 6 'Friendship 7' spacecraft did not rely on IEC International Standards. Several IEC TCs (Technical Committees) and SCs (Subcommittees) cover electronic components, assemblies and systems, as well as avionics. They include:
- IEC TC 47
In 1962, IEC TC 47: Semiconductor devices, and its SCs were only two years old and developing their first standards. IEC TC 47 prepares international standards for the design, manufacture, use, reuse, and testing of discrete semiconductor devices, integrated circuits, sensors, electronic component assemblies, interface requirements, and micro-electromechanical devices, using environmentally sound practices.
- IEC TC 91
Thirty years later, in 1990, IEC TC 91: Electronics assembly technology, was set up. The committee prepares international standards on electronics assembly (relevant) technologies and in the field of printed board assemblies, including the requirements for materials used to manufacture printed boards, electronic and electromechanical component mounting and optoelectronics assembly and attachment, as well as the electronic data format for describing these products and processes.
- IEC TC 107
IEC TC 107: Process management for avionics, was established in 2000 to develop process management standards on systems and equipment used in the field of avionics, including electronics for commercial, civil, and defense aerospace applications.
Conformity Assessment for avionics
The IEC also has put in place a conformity assessment system dedicated to the testing and certification of electronic components: IECQ, the IEC Quality Assessment System for Electronic Components. One of the IECQ Schemes deals specifically with avionics.
More specifically, IECQ has a scheme for the aerospace industry, IECQ ECMP (Electronic Component Management Plan), covering the component and assembly supply chain for avionics. This allows the aerospace industry to control the quality of the components it uses. IECQ is planning to use this Scheme in other high-reliability sectors such as railway and automotive industries.