Aeronautics and astronautics – Spacecraft – Attitude control
Reexamination Certificate
2003-03-21
2004-12-14
Dinh, Tien (Department: 3644)
Aeronautics and astronautics
Spacecraft
Attitude control
C244S11000H, C244S158700
Reexamination Certificate
active
06830222
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of provisional application 60/367,007, filed Mar. 21, 2002, which is incorporated hereby in its entirety by reference.
BACKGROUND OF THE INVENTION
1. Field of Invention
The present invention relates generally to space objects (including spacecraft, space vehicles, space satellites and space debris) and more particularly to a method and apparatus for lowering the orbit of a space object with respect to the Earth or some other celestial body.
2. Description of Related Art
Earth Orbital Debris Problem
The Earth has a mature and growing orbit debris and satellite problem. As of September 2001 the US Space Command tracks more than 2741 payloads and 6092 debris objects (greater than 10 cm in size) [MSFC Space Environmental and Effects Program (SEE) http://see.msfc.nasa.gov/]. It is estimated that there are more than 100,000 objects with size in the range 1.5 to 10 cm. All these objects are subjected to further impacts of other debris particles that can cause a cascade of debris once a critical mass of material is in an orbit. Occasional impacts of satellites create many fragments and particles. In addition, all these objects are affected by atomic oxygen erosion, which can cause paint to erode from surfaces increasing the debris environment.
In lieu of a national policy, the National Aeronautics and Space Administration (NASA) has established guidelines [“Guidelines and Assessment Procedures for Limiting Orbital Debris”] for mitigation of orbital debris that include limitations on released objects during normal operations, constraints on the probability of debris-causing explosions and collisions, control requirements on reentry location, and post-mission disposal. Post-mission disposal, practically speaking, calls for de-orbit of satellites at the end of their useful life.
The implication of planned de-orbit has been the carrying of additional propulsion system propellants in order to execute these de-orbit maneuvers at the end of mission. Some satellites have sufficient propulsion capability to lower their orbits or entirely de-orbit at end of life, but this requires additional mass. Unfortunately, the propulsive method of de-orbit requires additional mass be carried at launch that otherwise could have been used for mission equipment, and it also requires a cooperative satellite, that is, one that can receive and act on ground commands or execute long stored sequences. Failures of computers, power systems, or other key systems can make propulsive maneuvers impossible. Unfortunately, Earth orbit space vehicles that cannot afford the propulsive mass have no de-orbit provision whatsoever (e.g. Orbcomm satellites).
Reducing the debris problem is very important to the future use of LEO (low-earth orbit). It is now recognized that the debris problem can be mitigated by the elimination of debris-causing operations and by the removal of objects from orbit after they have achieved their useful life (e.g., old space stations, derelict satellites and used launcher stages).
Space Vehicles And Atmospheric Drag
Natural atmospheric drag operates by the exchange of momentum between the space vehicle and the molecules of the atmosphere. At high altitudes, where the atmosphere exhibits free molecular flow (where a molecule travels further than a characteristic length without colliding with another molecule), the space vehicle impacts molecules of air which either bounce off or stick to the space vehicle. If the molecule sticks, it imparts a momentum change to the space vehicle equal to the molecule's mass times the relative velocity of the molecule. On the other hand if a molecule bounces off the space vehicle, it imparts up to twice the momentum change. At lower altitudes, both drag and lift forces can be used to change the momentum of the space vehicle.
Space vehicles use entry capsules, heat shields or aeroshells, made of ablative materials or of materials that can withstand high temperature, to protect internal elements from the heating caused by atmospheric drag when reentering the atmosphere. Entry capsules, employed since the late 1950s, use atmospheric drag in order to slow space vehicles in the upper reaches of planetary atmospheres so they can descend to the surface of a planet. Also, concepts exist for ballutes (a word formed by a combination of balloon and parachute), which are robust, high-temperature-capable, inflated envelopes, for increasing the area of a space vehicle to reduce its velocity at a higher than usual altitude as compared to an aeroshell.
Entry Capsules
Entry capsules were used in the re-entry of the Mercury, Gemini and Apollo vehicles, and for planetary entry of the Viking Mars landers, the Pioneer Venus probes, the Galileo Jupiter probe and the Mars Pathfinder lander. These devices can be designed to change the natural entry trajectory of a space vehicle within the atmosphere to target the space vehicle to a particular landing zone as in the case of ballistic missile re-entry vehicles or Mars landing systems [Roy Smith, David Bayard and Ken Mease, “Mars precision landing: an integrated estimation, guidance and control simulation,” Center for Control Engineering and Computation (CCEC) report 98-0918, University of California, Santa Barbara, 1998]. Entry capsules primarily operate in the planetary Thermiospheres (lower levels) and Mesospheres. Entry capsules require massive thermal protection systems to protect the vehicle from the effects of atmospheric entry heating. The entry capsule mass can often be as much as 25% or more of the mass of the space vehicle itself. Extending the sizes of entry capsules to reduce the ballistic coefficient by one or more orders of magnitude is impractical due to the tremendous mass increase required. Furthermore, entry capsules are not amenable to low-volume stowage and use on uncontrolled space debris.
Aerocapture
Changing a planet-relative orbit from a very high-energy elliptical or a hyperbolic flyby orbit to a low energy elliptical or near circular orbit by means of a single pass to the mesospheric zone of an atmosphere is called aerocapture. Aerocapture has been analyzed extensively in recent years for use in orbit capture in order to reduce propulsion requirements. Aerocapture can be used by space vehicles to go into orbit around distant planets or it can be used at Earth to change the orbit of spent launch vehicle upper stages in order to place them into lower altitude, near circular orbits. Aerocapture systems use thermal protective surfaces oriented toward the atmospheric flow, or ram direction, to quickly decelerate a spacecraft (with a single deep atmospheric pass) from high velocity to orbital velocity. As with entry capsules, aerocapture requires the use of relatively massive aeroshells to protect their enclosed space vehicle from damage by atmospheric heating.
Aerobraking
Aerobraking is the use of atmospheric drag forces during repeated periapsis passes through the very high altitude, lower thermospheric zone of the atmosphere to take energy from an orbit as in circularizing an elliptical orbit. Aerobraking can be performed with unprotected space vehicles provided the altitude of the aerobraking process is high enough, where atmospheric densities are low, to reduce severe heating which could damage a space vehicle. When used, aerobrake devices are relatively large surfaces that can be deployed to increase the number of molecule collisions in order to increase the drag force and accelerate the process of reducing orbit energy. Aerobrakes can also function as protective surfaces to isolate the space vehicle from atmospheric heating during the periapsis passes in the atmosphere. If the cross-section area of a spacecraft can be increased, the aerobraking effect will be effective at higher altitudes, reducing heating of spacecraft surfaces, allowing the series of maneuvers to be completed more quickly and more safely.
Where aerobrake structures have been considered to protect the spacecraft and to provide additional d
Aaron Kim Maynard
McRonald Angus D.
Nock Kerry T.
Dinh Tien
Global Aerospace Corporation
Morrison & Foerster / LLP
LandOfFree
Balloon device for lowering space object orbits does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Balloon device for lowering space object orbits, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Balloon device for lowering space object orbits will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3296149