When a spacecraft is sent out in space, it requires a host of features and specifications to keep the crew, equipment and communications systems working with high efficiency and safety. The time span and the distance the spacecraft must travel demand that the systems have the upmost reliability.
Since 1957, when the Soviets launched the first artificial satellite, components which includes the hermetic connectors were constantly being modified and qualified to make space travel as safe as possible.
There have been several mishaps caused by unreliable parts and modules. In July 1999, 5 seconds after the Columbia space shuttle liftoff, an electrical short circuit caused controllers in the main engines to go haywire. If further damage had resulted, Columbia would have dropped into the ocean. Another incident happened on a NASA T-38 jet on May 10, 1972 when an electrical malfunction caused the loss of instrumentation during severe weather conditions. Fortunately, Astronaut Charles “Pete” Conrad was able to eject safely from the craft.1 In more current times, NASA and SpaceX postponed the launch of the new Dragon cargo spacecraft because of a power system glitch on the International Space Station. The delay was requested by engineers to tackle a power issue on the ISS that began on April 29, 2019. The problem was with one of the station's Main Bus Switching Units (MSU). The MSU distributes electricity for two of eight power channels on the station. The failed unit would eventually be replaced, and full power would be restored to the ISS. The Dragon cargo spacecraft was sent to rendezvous with the ISS once it had been repaired.2
There is no doubt that hermetic connectors are an integral part of the different systems that make spacecrafts tackle the space missions. Being a vital component, these connectors must be designed to handle the demands of space travel.
Conditions of Outer Space
There is no other place as hostile as outer space. The conditions are so extreme that hermetic connectors utilized require that they be able to handle these conditions without any failure. Outer space has very low pressure. The human body must therefore be contained in a spacesuit or else the body fluids would reach a boiling point. This is caused by the fact that fluids cannot evaporate entirely due to the rapid loss of heat energy. Hermetic connectors, especially those used in electrical components, must be able to ensure stable pressure on both sides of the assembly. The pressure in outer space is so low that many consider it non-existent. It has a pressure of 1.322 × 10−11 Pa.3
Hermetic connectors used in space are designed to prevent the entry of gases, air and liquids in the space vacuum. These connectors are designed to prevent any gas or fluid leaks. Leakage can cause considerable damage to the assembly contained within its packaging.
The extreme temperatures of outer space vary from one extreme to another. The temperature of space in sunlight is 120oC and can go down to -100oC which is way below the freezing point of water.4 The effects of such temperature swings on the human body can result in the expansion of the internal organs causing death within a minute. Connectors used in space are tested to handle these extreme temperature variations.
On August 11, 2018, NASA and the United Launch Alliance launched the Parker Solar Probe.5 The probe was launched using the enormous Delta IV heavy rocket, and by the end of 2024, the probe will have reached speeds of 430,000 mph or 692,000 km/h. This is when it will be closest to the sun (within 3.83M miles or 6M kilometers). This is the equivalent to travelling from Washington DC to Japan in less than a minute. The connectors used on the probe are made to withstand any rapid changes and robust enough to handle the extreme movements that occur on the voyage.
The Space Communication Requirements
All spacecraft have communication systems to send and receive vital instructions and from Earth. The spacecraft send data and information to Earth through these communication networks. The majority of launched space probes will never return to Earth. After launch, the tracking and communications systems are the only ways to interact with the spacecraft. Repairs and maintenance are made through the communications systems. Without the effective and efficient systems for data transfer, a space mission is most likely to fail. Specialized and highly qualified hermetic connectors are used for deep space communications.
The Deep Space Network or DSN is composed of three antenna complexes located around the world. The DSN is the ground network used for deep space communications. These complexes have hundreds of thousands of circular hermetic connectors linking various components and systems. These hermetically sealed connectors provide long-range performance in extreme environmental and physical conditions.
Hermetic Connectors for Space Electronics
For space electronics requirements, manufacturers have fabricated space-grade Nano-D connectors. These connectors are classified MIL-DTL-32139 nano miniature and have been approved for space use and inspected under EEE-INST-0026. The nano-D connectors are at .025″ pitch and are the smallest hermetic connectors. These connectors have also a reduced weight and size compared to the standard micro-D connectors.
These hermetically-sealed connectors comprise unique flex pin gold-plated contacts that are polarized and coated with liquid crystal polymer insulators. The pin-to-socket durability as well as the housing alignment system allows these connectors to have more than 2,000 mating cycles.
Connectors classified as space-grade are available in several tail terminations. The standard pre-wired connectors come in 18”, 36” and 48” length with 80 micro inches of silver plated 30AWG PTFE insulated wire. These connectors can be surface-mounted or through-hold varieties. Flex tails are also available for flex circuit use. The shell finish of such connectors includes stainless steel, titanium and nickel-place aluminum.
These hermetically sealed connectors pass through a standardized test procedure named ASTM E 595. This test evaluates the outgassing properties of polymers. When outgassing occurs, this can cause damage and contaminate instruments and optical surfaces.
Innovations in Design for Hermetic Connectors
NASA specification EEE-INST-002 has specific instructions on the evaluation and qualification of parts for use in the space programs.
Space-grade connectors are spin-offs of military-grade connectors. As the space program becomes more and more extensive and sophisticated, hermetic connector design engineers are now modifying mounting and shell formats based on specific requirements. Adjustments to existing formats are made in consideration of high shock, long flight duration and vibrations.
Materials and outgassing properties are carefully evaluated to make sure that it is suitable to protect the electronics inside the space box. These precautions are routinely made to ensure that the connector and other components are space qualified.
AMETEK-EIP Rises to the Challenge
To meet the need for space applications, AMETEK-EIP has been innovating hermetic connectors. These connectors are smaller, lighter and more reliable to be used spacecraft communication systems.
Discuss your connector needs with AMETEK-EIP’s experienced engineers and designers With any connector design requirements, AMETEK-EIP will rise to the challenge.
References:
1 https://en.wikipedia.org/wiki/List_of_spaceflight-related_accidents_and_incidents#1990%E2%80%931999
2https://www.space.com/spacex-dragon-cargo-ship-crs17-launch-delay.html
3https://www.newworldencyclopedia.org/entry/Vacuum
4 https://www.space.com/14719-spacekids-temperature-outer-space.html
5 https://www.nasa.gov/content/goddard/parker-solar-probe
6 https://nepp.nasa.gov/DocUploads/E9217401-8544-4DD6-B67488D4410E9762/conn.pdf