ASDS - Autonomous Satellite Docking System
AMDS Docking Sequence (Patent Pending)
Michigan Aerospace Corporation developed the technology for an on-orbit demonstration of autonomous
rendezvous and docking of two satellites to enable fluid/gas re-supply and payload exchange.
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Sponsors / Affiliates
DARPA Phase I SBIR
DARPA Phase II SBIR
The development of autonomous satellite servicing systems potentially
has a wide range of uses in both military and civil space programs.
Obvious applications in the military markets include re-fueling of surveillance
and reconnaissance satellites as one means to increase both their lifetime
and utilization factor. In the civil space sector, a similar need exists
to refuel operational systems that are fuel limited but whose data is
essential (e.g., communications, navigation, weather satellites).
ASDS is MAC's Solution for DARPA's Orbital Express
Space Operations Architecture
DARPA's Orbital Express Program intends to develop and demonstrate
autonomous satellite capabilities including re-fueling and on-orbit
satellite reconfiguration. For more information, take a look at DARPA's
Orbital Express website.
Advantages of ASDS versus Current Technology:
The cost of building and launching satellites limits the
number of assets that can be placed in orbit. This makes it critical
for the asset to have as long a lifetime as possible to reduce the replacement
rate. The primary limiting factor of satellite on-orbit lifetime is
its ability to maintain a useful, stable orbit, which in turn is limited
by on-board fuel at launch. There is also a growing requirement to give
satellites the ability to maneuver to new orbits on a regular basis,
including expensive plane changes. The ability of a satellite to change
orbits on a regular basis makes it less vulnerable to attack, allows
it to be repositioned to observe new crisis areas, and reduces the need
for multiple-satellite constellations to provide global coverage. This
comes down to the amount of fuel the satellite can carry to allow orbit
maneuvers and pointing changes. Since the amount of fuel that a satellite
can carry is limited by launch costs and weight limitations, the ability
to re-fuel a satellite on-orbit is the only method available to increase
its useful lifetime.
Satellite lifetime is also determined by failures of critical components.
If satellites were made to be serviced, it should also be possible to
"repair" the satellite using an automated payload-exchange system to
replace the damaged unit. In the past, several groups have looked at
the problem of making satellites more serviceable. Re-fueling or repairing
satellites using the Space Transportation System (STS - Space Shuttle)
is cost prohibitive, limited in terms of the orbit range of the STS,
and unnecessarily involves the use of astronauts. The Autonomous Satellite
Docking System (ASDS) would allow autonomous or semi-autonomous on-orbit
servicing without the use of STS.
In 1993, a low Earth orbit (LEO) demonstration for Autonomous
Rendezvous and Docking (ARD) was developed at the Space Automation
and Robotics Center (SpARC) and provided a near-term option for validating
many of the enabling technologies and concepts required for satellite
resupply and servicing. Flight hardware currently exists in the form
of a target spacecraft payload intended for a small satellite. The hardware
includes a docking mechanism, sensor targets, avionics, gas and payload
resupply interfaces for the target spacecraft, as well as a prototype
of the docking system for the chaser spacecraft. The on-orbit demonstration
was intended to validate that technology existed for performing autonomous
rendezvous and docking that could lead to propellant resupply for satellites,
fluid/gas re-supply for orbiting laboratories, and payload exchange
for satellites or servicing missions.
Michigan Aerospace Corporation has developed a mechanism for micro
satellite docking, which has been successfully demonstrated in a microgravity
environment. This docking mechanism is specifically designed for soft-docking
capability, tolerance to misalignment, and scalability. The current
Autonomous Micro satellite Docking System (AMDS) design resulted from
modifications to an earlier docking mechanism prototype that was tested
at the Marshall Space Flight Center (MSFC) Flat Floor Facility.
Autonomous Micro Satellite Docking System (AMDS):
The AMDS was tested in a microgravity environment through the NASA
JSC Reduced Gravity Program, under funding from the Air Force Research
Laboratory's Space Vehicles Directorate (AFRL/VS), Microcosm, Inc. and
Spectrum Astro. The Reduced Gravity office operates a KC-135 aircraft
that flies a series of parabolic zero-g maneuvers. The test objectives
of the KC-135 flight were to determine the docking mechanism cable assembly
behavior in zero-g, test the full range of the docking envelope in a
six degree of freedom test setup and determine the undocking capability
and stability. The nature of the Michigan Aerospace docking mechanism
enabled the entire docking cycle, including soft dock, auto-alignment
and hard dock, to be completed within the 20 seconds of 'zero-g' time.
Complete end-to-end docking and undocking was performed under a variety
of initial conditions and docking parameters. The data collected during
the KC-135 testing will be used to validate dynamic simulation models
of the docking mechanism. The intent of these dynamic models is to examine
a number of docking scenarios between a chaser and target satellite.
The results are described in the following papers: