MEV to the rescue – Hope for crippled satellites
ATK and ViviSat are working to demonstrate the ability to rescue satellites that are stranded in space after they run out of maneuvering fuel. The vision involves sending the Mission Extension Vehicle (MEV) to their aid, providing propulsion and attitude control systems, allowing the satellite to live on.
Satellite rescue isn’t a new concept, with the early days of the Space Shuttle resulting in the use of the orbiter’s range of capabilities to breathe new life into troublesome spacecraft.
One such example came via Shuttle Endeavour’s STS-49 mission in 1992, which focused on a rendezvous with the Intelsat VI satellite – which was stranded and unusable in Low Earth Orbit following its launch on a Titan rocket in March 1990 when its launch system failed to place it in its correct, geostationary orbit.
To facilitate the repair of Intelsat VI, a spacewalk was planned in which two of Endeavours crewmembers would physically grab the satellite and attach a capture bar to the satellite. During the spacewalk to grab the satellite, all attempts to grab Intelsat VI and attach the capture bar failed.
The EVA was subsequently called off and rescheduled for the following day, and Endeavour backed away to safe distance.
The next day, after a re-rendezvous, all attempts to capture Intelsat VI and install the capture bar failed as well.
Then, on May 13, a third attempt to capture the satellite was made using three of Endeavours crewmembers.
Before capture of Intelsat VI, an Assembly of Station by EVA Methods (ASEM) structure was erected by the crew to assist in the satellites capture.
The EVA was successful: Intelsat VI was captured, the capture bar attached, a live rocket engine kit installed (a kit that would propel Intelsat VI into its correct orbit), and the satellite released back into orbit.
The EVA marked the first and, to date, only time in history that an EVA was conducted involving three people, the first and, to date, only time that a live rocket kit was attached to a satellite in space during an EVA, and the longest single EVA in history to that point – a record that would stand until STS-102 in March 2001.
While such missions were impressive, they were restricted to Low Earth Orbit, were highly complex and hugely expensive, to the point they soon lost their viability.
However, a more innovative, cheaper and safer option for aiding malfunctioning or aging satellites is being developed by ViviSat.
At the center of their plans is the Mission Extension Vehicle (MEV), manufactured by one of its parent companies, ATK. The primary mission of the MEV is to dock with an orbiting satellite and serve as the propulsion and attitude control systems.
This enables mission extension for satellites that have run out of maneuvering fuel yet still have healthy payload and power systems.
“Life extension is the founding mission for the MEV. However, we have an increasing interest by customers and the scientific community in our unique agility and the large Space, Weight and Power (SWAP) that we can accommodate,” noted Bryan McGuirk, chief operating officer of Vivisat.
Such a technology could possibly have been used to come to the rescue of the Advanced Extremely High Frequency satellite (AEHF-1).
Despite a nominal launch atop of an Atlas V in August, 2010, a failure of the satellites subsystem resulted in the AEHF-1’s hydrazine-fueled liquid apogee engine (LAE) failing to carry out the required burns to place it correctly into Geostationary Orbit.
Thanks to some clever work via the satellites United States Air Force controllers and AEHF-1 teams, the $2 billion bird was saved via the ingenious use of the two smaller engines – namely the hydrazine-fueled Reaction Engine Assemblies (REAs) and later by the xenon-fueled Hall Current Thrusters (HCTs) – despite their primary role being one of positional stability on orbit.
The MEV – based on the ATK A700 satellite bus – is aiming to be multi-capable, which could result in it providing a platform for hosted payloads, before then being assigned to a life extension role.
“Hosted payloads can actually perform as the primary mission during the first several years of life of the MEV and then the MEV will revert to its original mission of life extension,” said retired Maj. Gen. Craig Weston, CEO of ViviSat. “This combination of prime mission flexibility, orbit location agility and large SWAP opens up a new market that cannot be met by typical GEO Commsats.”
As part of their forward plan, ViviSat are utilizing the ATK Robotic Rendezvous and Proximity (RPO) testing facility at the headquarters of ATKs Space Systems Division in Beltsville, Maryland.
The RPO facility enables ViviSat to demonstrate and verify critical enabling technologies for state-of-the-art robotic and air-bearing testbeds to simulate satellite motion and facilitate hardware and software development and validation.
“The MEV can host payloads greater than 200kg and accommodate power demands greater than 2kW. The differentiating feature of the MEV capability versus most other geo-stationary earth orbit (GEO) Commsat hosts is the ability to be temporarily located to any orbital slot, or multiple slots, as arranged for by the payload provider,” added Joe Anderson, chief engineer and director of MEV Services at ATK.
“Furthermore, there is no constraint on pointing or slewing like most other GEO hosts.”
ATKs Space Systems Division completed two prototype docking mechanisms that will reinforce the MEVs ongoing development.
“The ATK Robotic RPO Lab demonstrates a substantial investment in retiring risk for ViviSat and its clients,” Tom Wilson, vice president and general manager of ATK Space Systems Division, noted. “The capability currently demonstrated is the first step in our plans to perform full six degree of freedom docking validation and qualification.”
According to ATK, these prototypes demonstrate servicing capabilities to potential clients and will be used to validate contact dynamics and docking performance in the ATK RPO lab.
ATK also recently completed initial testing of closed loop proximity operations, demonstrating the ability to track a simulated host satellite using a prototype visual sensor suite.
“We demonstrated this closed loop capability to several clients and the response has been overwhelmingly positive,” added Bryan McGuirk, chief operating officer of ViviSat. “They see these developments as further validation that ViviSat is making key qualification milestones and demonstrating real capabilities to provide in-orbit servicing.”
(Images via ATK, Vivisat, ULA and L2 Historical)