Earlier this month, I gave a talk to the Environmental Caucus of the Sarasota Democratic Party on environmental issues in space: space debris, planetary defense, and planetary protection. I’ve blogged frequently here about planetary defense and planetary protection, so in this post I’ll focus on space debris.
Here’s my quick take on the space debris problem. The world is increasingly dependent on space-based services, for everything from communications to environmental monitoring, weather forecasting, and national security.A growing number of nations are building and launching their own rockets and spacecraft: the U.S., China, India, Japan, Russia….Actors in the space sector are increasingly concerned about the hazard of collisions between space assets and space debris.
Who’s keeping track of space debris? In the U.S., it’s a military operation, so limited information is available. In Europe, it’s a civilian operation, so more information is available.
The United States Space Surveillance Network (SSN) detects, tracks, catalogs and identifies artificial objects orbiting Earth – active and inactive satellites, spent rocket bodies, and fragmentation debris. The system is the responsibility of the Joint Functional Component Command for Space, part of the United States Strategic Command (USSTRATCOM).
The SSN says it has been tracking space objects since 1957 when Sputnik 1 was launched. Since then, the SSN has tracked more than 39,000 space objects orbiting Earth. Of that number, the SSN currentlytracks more than 8,000 orbiting objects. The rest have descended into Earth’s atmosphere and disintegrated, or (more rarely) survived entry and impacted Earth. Space objects now orbiting Earth range from satellites weighing several tons to pieces of spent rocket bodies weighing only 10 pounds. According to the SSN, about 7 percent of the space objects are operational satellites, the rest are debris. The SSN tracks space objects that are 10 centimeters in size or larger.
According to the European Space Agency’s (ESA’s) Space Debris Office:
- 5,000 satellites are in orbit around Earth, only 1950 of them still operational.
- 34,000 pieces of space debris that are 10 centimeters in size or larger are currently being tracked.
- 130 million pieces of debris smaller than 1 centimeter in size can’t be tracked.
- Debris is traveling in orbit around Earth at speeds up to 28,100 kilometers per hour.
- 500 collisions, break-ups, and explosions have already occurred in Earth orbit.
Antisatellite weapons (ASAT) testing since the 1960s has made some contribution to the space debris problem, though I did not find any authoritative source of information on the extent of the contribution. The U.S. government admits to working on ASATs from 1958 to 1988. However, in February 2008, the U.S. Navy destroyed a malfunctioning U.S. spy satellite using a ship-fired missile (a.k.a. Operation Burnt Frost). The U.S. government said it decided to shoot down this satellite because it carried toxic hydrazine fuel. China and Russia suspected that this operation was actually an ASAT test. Reuters reported in 2009 that Air Force Gen. Kevin Chilton, chief of the Defense Department’s U.S. Strategic Command, said, “Every bit of debris created by that (U.S.) intercept has de-orbited.” Chilton also claimed that some of the debris caused when China used a ground-based ballistic missile to destroy a defunct weather satellite in 2007 would remain in orbit for another 80 or 90 years.
China’s 2007missile-defense/anti-satellite system test reportedly created about 3,000 pieces of debris. Since then, the U.S. Defense Department claims, China has continued to develop anti-satellite weapons and conduct similar tests in 2010, 2013 and 2014, tests that apparently have not created debris.
Earlier this year, India conducted a missile-defense/anti-satellite system test that destroyed an Indian microsat, reportedly creating about 400 pieces of debris.
Also this year, the Indian Space Research Organization (ISRO) established a Space Situational Awareness Control Center to protect Indian space assets from space debris, near Earth asteroids, and adverse space weather conditions. ISRO says it plans to work on methods of active debris removal, space debris modeling and mitigation. It also plans to establish its own debris tracking system.
There are a lot of guidelines in place for mitigating space debris. How enforceable are they? Not much, I’d say. They’re guidelines, not regulations.
In 1995, NASA issued orbital debris mitigation guidelines. In 1997, the U.S. government established “Orbital Debris Mitigation Standard Practices” based on NASA’s guidelines. In 2007, an Inter-Agency Space debris Coordination Committee, organized by the United Nations Office of Outer Space Affairs (UNOOSA), published space debris mitigation guidelines.
Japan, France, Russia, and ESA have adopted orbital debris mitigation guidelines.
The U.S. Federal Aviation Administration’s Office of Commercial Space Transportation, which licenses space launches, requires licensees to complete a flight safety analysis, which includes, among other things, a debris analysis and a debris risk analysis:
“A debris analysis accounts for the debris produced by both normal events, such as the planned jettison of stages in an ocean, and abnormal events, such as destruction of the launch vehicle. This analysis must identify the inert, explosive and other hazardous launch vehicle debris that results from normal and malfunctioning launch vehicle flight. A debris analysis also requires a debris list, which is commonly referred to as a ‘‘debris model,’’ and must account for each cause of launch vehicle breakup. The debris lists describe and account for all debris fragments and their physical characteristics. A debris model categorizes, or groups, debris fragments into classes where the characteristics of the mean fragment in each class represent every fragment in the class. These debris lists are used as input to other flight safety analyses, such as those performed to establish flight safety limits and hazard areas and to determine whether a launch satisfies the public risk criteria of section 417.107.A debris risk analysis determines the expected number of casualties to the collective members of the public, if the public were exposed to inert and explosive debris hazards from the proposed flight of a launch vehicle. “
Last year, the Federal Communications Commission (FCC), which licenses the operation of U.S. comsats, proposed a new rule intended to update its 2004 orbital debris mitigation requirements:
“In several recent instances, applicants have sought to deploy satellites using mechanisms that detach from or are ejected from a launch vehicle upper stage and are designed solely as means of deploying a satellite and not intended for other operations. Once these mechanisms have deployed the onboard satellite(s), they become orbital debris.”
“Certain types of liquids, such as low vapor pressure ionic liquids, will, if released from a satellite, persist in the form of droplets. At orbital velocities, such droplets can cause substantial or catastrophic damage if they collide with other objects. In the last several years, there has been increasing interest in the use by satellites (including small satellites) of alternative propellants and coolants, some of which would become persistent liquids when released by a deployed satellite. The Commission also expects that the orbital debris mitigation plan for any system utilizing persistent liquids should address the measures taken, including design and testing, to eliminate the risk of release of liquids, and to minimize risk from any unplanned release of liquids.”
In June, Stijn Lemmens, ESA’s senior space debris mitigation analyst, had this to say:
“Several nations have launched almost 9,000 satellites over the past six decades. Of these, about 5,000 are still in orbit. So we are talking about doubling the amount of traffic in space over a couple of years, or over a decade at most, compared to the last 60 years.”
“The space debris issue is mostly caused by the fact that we leave objects behind in orbit, which are then a target for collisions either with fragments of a previous collision event or with big, intact objects. Currently, most space debris comes from explosive breakup events; in the future, we predict collisions will be the driver. It’s like a cascade event: Once you have one collision, other satellites are at risk for further collisions.”
“Over the past two decades, there has been a lot of effort to establish guidelines and codes of conduct. For low-Earth orbit (LEO), there is a well-known guideline to take out your spacecraft, satellite, or launch vehicle upper stage, within 25 years after the end of mission. To have a reasonable shot at having a stable space environment, the goal is to have at least 90% of the satellites and launch-vehicle upper stages with lifetimes longer than 25 years take themselves out of orbit, or put themselves into orbits with lifetimes less than 25 years.”
“However, we are not really good at doing this at the moment. We’re talking about success rates of 5 to 15 percent for satellites (launch vehicle orbital stages do notably better, with success rates of 40-70% in low-Earth orbit). Already with current traffic, we have reasonable concerns that we’re creating a real debris issue out there.”
In 2018, Swarm Technologies bypassed the required FCC approval process for sending communication satellites into space, launching four experimental communication smallsats. In December 2018, the FCC fined Swarm $900,000 for launching and operating these smallsats without approval.
In May of this year, SpaceX launched the first 60 of a proposed constellation of 12,000 Starlink communication smallsats. SpaceX claims its Starlink satellites “are designed to be capable of fully autonomous collision avoidance.” (I guess time will tell whether this capability is functional.)
My next blog post will be about space debris removal technology developments and demonstrations.