Hand in the sky - A System for Removal of Large Orbital Debris
An effective orbital debris removal and relocation system is critically needed, given the large amount of debris, such as spent rocket bodies and dead satellites, in low Earth orbit (LEO). Presently, thousands of space debris objects are being tracked in order to allow planners to place new systems in an unobstructed orbit, or to help operators to manoeuvre space systems to avoid collision with space debris. Orbital debris poses disastrous interference and collision threats to neighbouring satellites, leading to actual collision incidents. The recent 2009 collision of the active Iridium 33 satellite was the first accidental hyper-velocity collision between two intact artificial satellites in LEO. 
At present, there are no proven means to relocate a satellite to a super synchronous burial orbit, or to deorbit it to burn in the Earth’s atmosphere.
The Aerospace Corporation patented a satellite capture system called WALDO, which offers a possible solution via a “hand in the sky” device. WALDO was inspired by “WALDO
& Magic, Inc,” a Robert Heinlein science fiction novel, in which the protagonist creates robotic hands, called Waldos, varying in size from microscopic to gigantic. The patented “satellite grabber” comprises a base satellite which, once in orbit, commands pneumatic deployment of long, slender, finger-like pods. The pods can be articulated by longitudinal tendon-like articulations, acting like a finger that curves around and captures the object. A combination of three such pods forms a “hand in the sky,” a Waldo, that captures the case, target objects are assumed to be passive and non-cooperative, as would be expected when collecting random dead satellites. The major advantage of WALDO is its ability to approach a target object from the front, embracing it all around with a controllable soft grab that would not damage appendages.
WALDO was inspired by the Jet Propulsion Laboratory (JPL) Inflatable Antenna Experiment (IAE) of May 1996. The IAE was released from the shuttle and was deployed by inflation. The long sub-reflector pods and the main large space structure. These long slender pods, which extend far out in front of the sub-reflector to form a capture zone, are what inspired WALDO. In WALDO, the pods have articulation tendons running along the length of the spacecraft, enabling these sorts of large “fingers” to curve around and grab a space object.
Concept of Operations
A detailed end-to-end mission concept of operations (CONOPS) for WALDO has been developed. A one metric ton space object, located at 400-600 km, would be captured and then either moved to a suitable burial orbit or deorbited. The CONOPS includes: analysis and assessment of the propulsion system; deployable mechanisms and deployable inflatable articulating fingers; long-range and close-in navigation and control; real-time image processing and target attitude; precise autonomous motion control to achieve formation flying; docking to target; removal to desired orbit or deorbit; control satellite/spacecraft sizing; design, fabrication and test plans; and flight demonstration test plans.
The CONOPS starts with a dead satellite, slowly rotating in a drifting orbit, which must be moved to a burial orbit. Ground tracking details of the target object are programmed into WALDO, along with detailed characteristics and images of the target satellite. WALDO plans the rendezvous trajectory using autonomous navigation, based on the NASA Advanced Video Guidance Sensor (AVGS) demonstrated in the Orbital Express Project. WALDO, which is also capable of close-in navigation, approaches the target using optical or 
imaging radar to establish orientation and motion of the object, and plans the final approach and capture. Navigating to a concentric rotation axis, WALDO establishes formation flying with the object, similar to the way in which the Space Shuttle and the Hubble tele-scope manoeuvre during repair missions. As soon as WALDO nears the object at a distance suited to deployment of the fingers, around one to ten meters, the grasping fingers are pneumatically deployed. The fingers are sized and arranged to surround the selected de-bris object; as an example, the fingers can be thirty meters long, oriented at about 120° angles. The target is then captured as the fingers embrace it in padded physical contact. When the de-bris is within reach, the motor mechanism pulls and tightens the tendon lines causing the fingers to wrap around the debris to secure the grasp.
imaging radar to establish orientation and motion of the object, and plans the final approach and capture. Navigating to a concentric rotation axis, WALDO establishes formation flying with the object, similar to the way in which the Space Shuttle and the Hubble tele-scope manoeuvre during repair missions. As soon as WALDO nears the object at a distance suited to deployment of the fingers, around one to ten meters, the grasping fingers are pneumatically deployed. The fingers are sized and arranged to surround the selected de-bris object; as an example, the fingers can be thirty meters long, oriented at about 120° angles. The target is then captured as the fingers embrace it in padded physical contact. When the de-bris is within reach, the motor mechanism pulls and tightens the tendon lines causing the fingers to wrap around the debris to secure the grasp.
After capture, WALDO determines the removal trajectory to the disposal orbit, or the deorbit manoeuvre for the debris object, and fires its thrusters accordingly, performing either an insertion into outer super synchronous disposal orbit or a deorbit manoeuvre.
Source: Space Safety, Spring 2012
The human body has adapted over millions of years to work and operate within the gravity field. The musculoskeletal system is sized to act, jump, grip, grasp, carry loads, move,maintain balance, and use and define all the motor control strategies which are necessary for a safe life on Earth.
The absence of gravity makes working in a spacecraft physically undemanding. In a weightless environment, very little muscle contraction is needed to support the body and move around. Such effortless motion results in weakening of calf muscles, quadriceps and the muscles of the back and neck in a process called atrophy. An astronaut can experience a muscle mass loss as high as 5% a week.
Even the heart is affected by atrophy. In space, blood pressure is about 100 mmHg throughout the body, with no differential between head and feet. When bodily fluids redistribute themselves in the new environment, astronauts ap-pear to have swollen faces and thin legs. The lack of blood pressure gradient means less blood is needed, causing the body to excrete about 22% of its blood volume. The heart doesn’t need to pump as hard to distribute the blood, there-fore it atrophies.
pump as hard to distribute the blood, there-fore it atrophies.
If one could remain in space forever, muscle loss would not be a problem, but when crew members return to Earth their bodies have to readjust to gravity. Most space adaptations appear to be reversible, but the rebuilding process is not necessarily easy. While blood volume is typically re-stored within a few days, muscle recovery takes about a month. Bone loss is even more problematic, taking up to three years to recover.
Zero-G Exercise
The only way to minimize muscle atrophy in space is through intensive strength training exercise – up to 2.5 hours a day. But exercising in space is only effective if it entails some gravity-like resistive force. On ISS, this resistance is provided by strapping an astronaut to a treadmill with bungee cords. The straps are not particularly comfort-able, so astronauts can only exercise with loads of 60-70% of their body weight. Astronauts can include squats, dead lifts, heel lifts, and various presses and curls in their routines using the Advanced Resistive Exercise Device (aRED), which can provide more than 270kg of resistance.
Even though these machines are partially effective in mitigating the effects of weightlessness on muscles, increasing loads on muscles and bones is not enough without taking care of fluid flows.
Chibis aims to do just that. It is a Russian below-the-waist suit that applies suction to the lower body, simulating a gravity-like stress to the body’s cardiovascular system. In the days before returning home, cosmonauts perform a preparatory training in the suit consisting of drink-ing 150-200 millilitres of fluids, followed by a sequence of progressive regimes of negative pressure (from -15 to -30 mmHg) for five minutes each while shifting from foot to foot at 10-12 steps per minute. This protocol induces the body’s circulatory system to interpret the pressure differential be-tween upper and lower body as a gravity-like force pulling the blood (and other liquids) down. The exercise prevents much of the loss of cardiovascular function and of muscle, and may also be effective in reducing bone loss.
Source: Space Safety, Spring 2012
