Epistemic status: Uncertain, shooting from the hip a little with no expertise in this area and only a couple of hours research done. I might well have missed something obvious, in which case I’ll revise or even take the post down.
Money Waste is Everywhere
Here in Northern Uganda where poverty abounds, many expenditures feel wasteful. Last night I had a great time at the fanciest restaurant in town with friends but felt a pang of guilt about my $7 meal. Enough of a pang to avoid telling my wife after I came home.
A bigger scale waste in these parts is the partial closure of the main bridge across the river Nile, because the bridge has apparently degraded and become hazardous. Vehicles larger than a minivan now can’t cross, which has raised the price of public transport by 50% and trucks now have a 3 hour detour. Besides these direct costs, this closure increases the cost of fuel and commodities in Northern Uganda. By my loose, conservative BOTEC the closure costs $10,000 every day (1.2 million dollars in 4 months so far) which Ugandans now can’t spend on education and healthcare, while likely causing more crashes due to increasingly tired drivers who now use worse roads. The detour itself may have already cost more lives than would be lost if the bridge does collapse and kills a few people.[1]
But there are far bigger wastes of money on this good earth.
A Billion Dollars to bring down a space station?
Space X have secured an 843 million dollar contract[2] to build the boringly named “U.S. De-Orbit vehicle” (why not "Sky Shepherd")[3], which in 2031 will safely guide the decommissioned International Space Station (ISS) into the Pacific Ocean. This all sounded pretty cool until I thought… is this worth it?.
No human has ever been definitively killed by an object falling from space, although there have been a couple of close calls with larger asteroids injuring many while Open Asteroid Impact could be a game changer here in future. This one time though, a wee piece of space junk did hit Lottie Williams in the shoulder and she took it home as a memento. I’m jealous.
According to a great Nature article “Unnecessary risks created by uncontrolled rocket reentries”, over the last 30 years over 1,000 space bodies have fallen to earth in uncontrolled re-entries and never killed anyone. The closest call might be a Chinese rocket in 2020 which damaged a house in the Ivory Coast. The article predicts a 10% chance of a fatal space junk accident in the next 10 years – far from zero and worth considering, but unlikely to be the next EA cause area. This low risk makes sense given that only 3% of the globe are urban areas and under 1% actually contain human homes[4]– most stuff falls down where there ain’t people. Also the bulk of falling spacecraft burns up before hitting the ground.
In contrast a million people die from car crashes every year,[5] and each of us has about a 1 in 100 chance of dying that way.
Although the ISS is the biggest ever at 450 tons, we do have priors. Two 100 ton uncontrolled re-entries (Skylab and tragically the Columbia) crashed to earth without issue. So what actually is the risk if the ISS was left to crash uncontrolled? The U.S. Government requires controlled re-entry for anything that poses over a 1 in 10,000 risk to human life so this risk must be higher. NASA doesn't give us their risk estimate but only state “The ISS requires a controlled re-entry because it is very large, and uncontrolled re-entry would result in very large pieces of debris with a large debris footprint, posing a significant risk to the public worldwide” [6].
I hesitate to even guesstimate the risk to human life at the ISS falling, but I’ll throw out a number. Given we’ve had over 1,000 (albeit smaller) spacecrafts fall without a death yet, and the Nature paper estimates a 10% chance of death from the 600 spacecraft which will fall over the next 10 years, I’d be hard pressed to estimate anything higher than between a 1 in 100 and 1 in 1,000 chance of a deadly crash, although multiple casualties would be possible.
100 Billion per life saved?
That would mean that the projected cost per life saved might be over 100 billion dollars here – I’m not pitching this safety project to GiveWell. This could make the controlled descent of the ISS one of the largest, least cost-effective safety initiatives of our time.
Yes NASA has other considerations, like getting sued for breaching government safety standards, and the PR disaster as millions of us sit at home in 2031 glued to our screens, irrationally worrying more about the ISS hitting our home than we are getting in their car the next day - but these hardly seem billion dollar concerns. NASA might also be keen to maintain their good reputation as a steward and leader of space governance, as they try and keep the moral high ground while working on other important agendas like reducing space junk. (Thanks @David T)
Although stopping this government expenditure seems intractable at this point, I think its helpful to consider waste on all scales from time to time, especially when its our own tax money paying the bill.
have no expertise at all in this field so I might just be missing something obvious, so feel free to correct and fire away .
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Karuma Bridge is only 70 meters long with only 1 - 3 vehicles crossing at any one time.
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https://www.nasa.gov/news-release/nasa-selects-international-space-station-us-deorbit-vehicle/
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Even ChatGPT did better with “Sky Shepherd”, “Descender X” and “Stellar Dropper"
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https://www.researchgate.net/publication/261718817_How_much_of_the_world's_land_has_been_urbanized_really_A_hierarchical_framework_for_avoiding_confusion
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https://www.who.int/news-room/fact-sheets/detail/road-traffic-injuries#:~:text=Approximately%201.19%20million%20people%20die,adults%20aged%205%E2%80%9329%20years.
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https://www.nasa.gov/news-release/nasa-selects-international-space-station-us-deorbit-vehicle/
Needless to say, NASA does not use EA math in its budgeting ;-)
The world's major space agencies abandoning the biggest thing we ever put into space in an uncontrolled deorbit is a politically untenable option (and the project represnts only around a third of the estimated $3bn annual budget to keep the ISS operational, although there's an argument this spend has more ROI...). That's even more the case against a backdrop of increasing calls for more regulation around everyone else's launches and orbits and deorbits to prevent collisions in space[1]
The potential risk to human life of uncontrolled ISS reentry therefore isn't the only factor in the decision and probably not even the main one, though I don't think the deorbiting of generally orders of magnitude smaller stuff gives much of a guide to the magnitude of that risk.[2] (There are of course also other arguments against spending money on this project, such as the desirability of maintaining the ISS, the possibility of raising it to a graveyard orbit for future reuse/recycling instead of destroying it; and other arguments in favour such as the likelihood at least some of SpaceX's R&D can be deployed to more productive projects in future). Space agencies usually aren't especially rigorous in analysing cost effectiveness anyway, but cost-per-life saved is a pretty minor factor in why such contracts are awarded. Space funding is industrial policy targeting notionally large medium term returns from technology, not evidence-based philanthropy trying to find the most cost effective way to remedy problems.
this potentially compounds, with each debris impact creating more orbital debris, with the theoretical possibility of rendering some orbits unusable in future. Avoiding this scenario might still seem wasteful from the point of view of a Ugandan farmer whose neighbourhood could be fed for years on the research budgets being devoted to maintaining congestion-free orbits, but rather a lot of the developed world depends on access to satellite technology and I suspect even some NGOs in Uganda make some use of GPS and satcomms.
but that risk is probably still low, assuming even with it rentering via gradual orbital decay, operators would still have sufficient ability to control reentry using onboard thrusters to direct it to scatter it's debris over thousands of kms that's mostly ocean or sparsely populated, as with Skylab...
Just to clarify on the orbital debris problem: it's not just the risk of the ISS specifically hitting things on the way down (which is non-zero but at the same time not that likely: the ISS is too big to overlook and will move in a reasonably predictable manner so things will generally adjust their orbits in advance to move out the way, and most of them have higher orbits anyway). It's also that when operators of thousands of other satellites[1]- from Starlink to university cubesats - are being advised/required to have specific end-of-life deorbiting strat... (read more)