An increasing amount of space debris in low- Earth orbit (LEO), roughly less than 1,600 kilometers above the Earth’s surface, is putting both manned and unmanned missions at heightened risk, according to D.K. Sachdev, president of Vienna, Va.-based SpaceTel Consultancy. (Read OOW's Profile of D.K. Sachdev)
LEO is more dangerous than geosynchronous orbit (GEO), where satellites orbit at an altitude of 36,000 kilometers above the Earth, due to a larger number of space debris objects that travel at a higher relative velocity, said Sachdev, an inductee in the Society of Satellite Professionals International (SSPI) Hall of Fame. Without changes to limit space debris produced from future missions, the problem will only worsen.
One technique that would help to reduce the amount of space debris would be to develop hardware for launch vehicles that would disintegrate and burn in orbit, Sachdev said. Almost all of the hardware from launch vehicles stays in LEO, except for the pieces that drop in the sea or are recovered and reused.
“The hardware remaining in LEO poses risk to orbiting objects and also to human flights to space,” Sachdev said.
In GEO, if operators diligently follow the guidelines for raising the orbit of satellites that reach their end of life, the risk to “operational missions” is mitigated substantially
After launch vehicles, the next biggest source of space debris comes from large structures in LEO that were left behind after their useful life ended. For example, an imperfect launch can leave a large spacecraft hurtling in non-standard, inclined orbit without any ability to control it.
Manned missions passing through a “growing mass” of debris in LEO are also increasingly vulnerable, Sachdev said.
“With the privatization of manned missions around the corner, clear guidelines and access to debris databases should be provided to new entrepreneurs for their launch-mission planning.”
Databases to monitor space debris are undergoing constant updating by designated agencies of the United States, the European Space Agency (ESA) and others. Guidelines have been established by the International Telecommunication Union (ITU), the U.S. Federal Communications Commission (FCC) and other regulatory bodies about the end-of-life residual fuel that must be reserved for orbit-raising purposes only.
However, those guidelines may not be followed in every case for two main reasons: “genuine uncertainties” in the measurement accuracies of on-board fuel gauges and delays in the availability of replacement spacecraft that may force operators to deviate from the guidelines .
“The former requires efforts by industry to improve measurement accuracies and the latter suggests higher schedule margins in system-replenishment planning,” Sachdev said.
Natural space debris takes the form of meteoroids, interplanetary dust, etc.“However, such debris largely consists of smaller particles and is at a steady level,” Sachdev said. In comparison, man-made debris generally consists of larger particles and masses that are increasing amid a growing number of space activities.
As far as precautions, short-term mitigation requires greater industry discipline and awareness, as well as diligent compliance with regulatory guidelines.
“This should include widespread adoption of hardware design and configuration principles that make a large structure break into small pieces,” Sachdev said.
Long-term mitigation would involve finding a way to launch spacecraft by using something other than “chemical technology.”
Despite “impressive” progress for nearly the past century, almost 80-90% percent of the total mass of a launch vehicle ends up either as burnt fumes, “contributing to global warming,” or as an “unwelcome addition” to space debris.
In the face of “seemingly” insurmountable hurdles in basic material technologies, innovation still needs to be pursued to sustain the unique contribution of commercial and government satellites well into the future.
Launch service providers constantly look at deploying “reusable hardware,” mainly to reduce costs. Such efforts can also ameliorate launch-related space debris from remaining a serious threat.
The potential benefits would be increased safety and slightly reduced global warming for “our grandchildren,” Sachdev said.
In addition to his consulting work, Sachdev also serves as an adjunct faculty member at George Mason University, where he teaches a graduate-level course in system engineering for telecommunications systems.
Sachdev, who held key engineering positions at Intelsat between 1978 and 1996, started managing research and development when he first arrived at the satellite organization and later led system planning and several engineering functions there. His top accomplishments at Intelsat included leading the planning and engineering of two major spacecraft programs: Intelsat VII7/VII7A and Intelsat VIII8.
Earlier in his career, Sachdev held several senior positions at the Indian Telecommunications Service and in private industry. In recognition of his lifetime professional achievements, he received the Arthur C. Clarke Innovator’s Award in 2003. He has also authored two books about satellite systems.
Paul Dykewicz is a seasoned journalist who has covered the development of satellite television, satellite radio, satellite broadband and hosted payloads.