Falling space debris is real, and it's going to require global action to fix

In space exploration news, a study published Monday in the journal Nature Astronomy explores the dangers associated with rocket part reentries. According to the study, far from being an insignificant risk, falling bits of rockets should be considered a very real danger. 

According to the study, the majority of space launches result in uncontrolled rocket body reentries, posing a risk of casualties to those on land, at sea, and in aircraft. Although these dangers have long been considered insignificant, more rocket bodies are being left in orbit while older rocket bodies continue to reenter the atmosphere as a result of gas drag. 

The study aimed to estimate the approximate casualty expectations due to rocket body reentries as a function of latitude using data from launches and abandoned rocket bodies in orbit. It found that the casualty expectation (i.e., danger to human life) is disproportionately carried by populations in the Global South as a result of the distribution of rocket body launches and reentries, with major launching governments exporting risk to the rest of the globe.

Michael Byers, the study lead, and his colleagues did this by analyzing 30 years of data to calculate the risk of uncontrolled rocket re-entry into Earth's atmosphere. The analysis shows that, under existing methods, if a typical rocket re-entry distributes debris over 108 feet² (10 m²), there is a 10 percent chance of one or more casualties over the next decade.

Boosters and other large rocket parts fall to Earth or are left in orbit. Abandoned rocket parts can then reenter the atmosphere uncontrollably, and debris might drop wherever along the flight path. They also found that rocket bodies are three times more likely to land in Jakarta, Dhaka, and Lagos than in New York, Beijing, or Moscow.

Armed with this knowledge, the researchers contend that the majority of these uncontrolled reentries are no longer essential because of recent advancements in technology and mission design, but launching states and businesses are reluctant to shoulder the resulting additional expenses.

In the researcher's view, uncontrolled rocket reentry is becoming a choice, not a technological limitation. Controlled reentries from orbit require reigniting engines to steer the rocket body away from populated areas, usually into the ocean.

What's the problem? 

According to the study, some launch providers still utilize older rocket types without reigniting engines, and they must be modified or replaced for safe, controlled return. Controlled reentry demands more fuel beyond what's needed for launch. Some launch providers using current rockets with reignite engines consume fuel to boost the cargo as high as possible, saving clients time and fuel.

In doing so, providers forgo a controlled reentry. To ensure a safe, controlled re-entry, mission design must be altered, according to the study.

But, the authors point out, these steps cost money. In the instance of the Delta IV rocket, the U.S. government allegedly granted waivers due to exorbitant upgrade costs, despite being well-positioned to bear the extra cost of safer missions. In commercial missions, controlled reentry costs could limit a launch provider's ability to compete. Internalizing safety, environmental, and other externalities often increases costs.

Governments need to make a joint effort to reduce the risk of falling rocket parts

To mitigate the problem, the study says, rules and regulations guarantee a level playing field so no company, even a new entrant, loses from improved practices. To this end, the authors argue, national governments could raise launch rules for their territory or for domestic enterprises.

Individual governments may have competing incentives, such as cutting costs or creating a domestic space sector. Uncontrolled rocket reentry is a “collective action problem” which every launching state must implement remedies.

This, the authors argue, should be possible as there are precedents for this kind of action in the past. In the 1970s, for example, scientists warned that CFCs used in refrigeration systems were decreasing ozone molecules in the atmosphere, allowing more cancer-causing UV light to reach the surface.

Subsequently, the "Ozone Layer Vienna Convention" was adopted in 1985. This was followed by the 1987 "Montreal Protocol on Substances that Deplete the Ozone Layer" which created a framework for phasing out CFCs. These two ratified accords have overcome the so-called “collective action dilemma”. And they worked, as a result, global CFC use by fell by 98 percent, averted additional damage to the ozone layer, and prevented two million skin cancer deaths annually.

In the 1970s, oil spills threatened oceans and coastlines, and national and international attempts were made to require double-hulled tankers. Concerned about rising expenses, the shipping industry stymied these attempts until 1989, when the Exxon Valdez dumped 11 million gallons of oil into Alaska's Prince William Sound. After media coverage of the tragedy made oil spills a public concern, the US government mandated all new tankers calling at US ports to have double hulls.

This unilateral decision created the “International Maritime Organization” to alter MARPOL in 1992 to mandate double hulls on new tankers and in 2001 and 2003 to expedite the retirement of single-hulled tankers.

150 states (including the USA, Liberia, and Panama) representing 98% of global maritime tonnage have accepted the 1992 MARPOL amendments. This precedent of oil spills and the double-hull requirement is especially significant for uncontrolled rocket body reentries because it concerns transportation safety beyond national authority, with oil spills creating problems for all coastal states.

To this end, the authors advise that national governments whose citizens are at disproportionate risk from uncontrolled rocket bodies should insist that major spacefaring states impose regulated rocket reentries, create substantial sanctions for noncompliance, and eradicate all risks. Since they hold a majority in the United Nations General Assembly, they may negotiate a non-binding resolution or a treaty if needed.

An international treaty may not be approved by the main spacefaring powers, but it would still raise awareness and set new expectations. The 1997 “Anti-Personnel Landmines Convention” resulted in a decline in the global usage of antipersonnel mines, with non-ratifiers changing their behavior.

On the subject of uncontrolled rocket body reentries, Global South states retain the moral high ground: their citizens bear most of the risks, which is unnecessary since the technologies and mission designs to prevent casualties already exist, the authors conclude. 

Study abstract: 

Most space launches result in uncontrolled rocket body reentries, creating casualty risks for people on the ground, at sea, and in aeroplanes. These risks have long been treated as negligible, but the number of rocket bodies abandoned in orbit is growing, while
rocket bodies from past launches continue to reenter the atmosphere due to gas drag. Using publicly available reports of rocket launches and data on abandoned rocket bodies in orbit, we calculate approximate casualty expectations due to rocket body reentries as a function of latitude. The distribution of rocket body launches and reentries leads to the casualty expectation (that is, the risk to human life) being disproportionately borne by populations in the Global South, with major launching states exporting risk to the rest of the world. We argue that recent improvements in technology and mission design make most of these uncontrolled reentries unnecessary, but that launching states and companies are reluctant to take on the increased costs involved. Those national governments whose populations are being put at risk should demand that major spacefaring states act, together, to mandate controlled rocket reentries, create meaningful consequences for non-compliance and thus eliminate the risks for.