Acute abdominal pain is a medical emergency which requires diagnostic facilities not available on board spacecraft. It could require emergency return from LEO or mission abort in cislunar missions. One of the causes of acute abdominal pain is renal stones.


Bone loss and renal stone risk are longstanding concerns for astronauts. Bone resorption brought on by spaceflight elevates urinary calcium and the risk of renal stone formation... Regardless of exercise, the risk of renal stone formation increases during spaceflight. A key factor in this increase was urine volume, which was lower during flight in all groups at all time points. Thus, the easiest way to mitigate renal stone risk is to increase fluid consumption.

Prolonged microgravity causes significant calcium loss in bones (10 times the rate seen in Earth-bound osteoporosis), thereby increasing the risk of kidney stones. https://www.nasa.gov/mission_pages/station/research/benefits/bone_loss.html

Between 1% and 15% of people globally are affected by kidney stones at some point. In 2015, they caused about 16,000 deaths worldwide… By far, the most common type of kidney stones worldwide contain calcium. https://en.wikipedia.org/wiki/Calcium_oxalate#Kidney_stones

Acute abdominal pain in an ISS crewmember would necessitate return to Earth, along with the other crew in that Soyuz/Crew Dragon crew group. The same event on a Lunar mission would cause a mission abort. On a Mars mission...?

Since the risk of kidney stones can be reduced by maintaining adequate urine volume, "which was lower during flight in all groups at all time points", does NASA routinely “police” astronaut urine production (monitor urine production and enforce fluid consumption)?

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    $\begingroup$ Might it be less messy to police fluid intake? $\endgroup$ Dec 14, 2021 at 17:15
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    $\begingroup$ Space travel is not for the squeamish! Dilution of calcium salts is critical. As well as oral fluid intake, urine volume is affected by perspiration, respiratory loss and metabolic water production . Urine collection also allows measurement of salt concentrations and trace blood detection which can be the first diagnostic sign of stones. $\endgroup$
    – Woody
    Dec 14, 2021 at 17:34
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    $\begingroup$ @BrendanLuke15 they process the urine on the US side of the ISS (or they did in 2014 when I got out of the game) space.stackexchange.com/q/49419/6944 space.stackexchange.com/a/26745/6944 space.stackexchange.com/a/45727/6944 $\endgroup$ Dec 14, 2021 at 18:20
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    $\begingroup$ Woody can you define what you mean by "police"? Do you mean "monitor", or do you mean "enforce a certain amount of production per individual"? $\endgroup$ Dec 14, 2021 at 18:24
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    $\begingroup$ By "police" I mean "monitor and enforce" rather than just measure. Urine volume... "which was lower during flight in all groups at all time points" indicates that self-motivated fluid intake by astronauts is insufficient to compensate for increased calcium excretion. This increases the risk of preventable mission-threatening medical emergencies. $\endgroup$
    – Woody
    Dec 14, 2021 at 18:57

1 Answer 1


For shuttle:

  • There was no enforcement of and no policy existed regarding urine production per crewmember.
  • Even if such a policy had been desirable, there was no way to monitor per-crewmember urine production.

The shuttle toilet (formally, "Waste Collection System (WCS)") had no telemetry associated with it. (See this answer for a WCS overview) The responsible flight control group EECOM had to infer when toilet ops were ongoing by monitoring other signatures in the orbiter systems:

  • AC current signatures from operation of the WCS fans
  • Change in pressure over time (dp/dt) of the cabin atmosphere for a toilet flush
  • Quantity changes in the waste water tank

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Source: Shuttle ECLSS Training Manual (annotations mine)

This answer does not apply to dedicated life science experiments such as those conducted during the Spacelab Life Sciences missions which may have monitored per-crewmember urine production using a Urine Monitoring System.

  • $\begingroup$ Individual 24 hour urine collections were performed on ISS 3-6,8, and 11-14 as part of the potassium citrate stone prevention study. ntrs.nasa.gov/api/citations/20070008213/downloads/… Results showed markedly lower stone formation risk with higher 24hr urine volumes. $\endgroup$
    – Woody
    Dec 14, 2021 at 23:04
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    $\begingroup$ @Woody your comment appears irrelevant to this shuttle-focused answer. $\endgroup$ Dec 14, 2021 at 23:06
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    $\begingroup$ Since the shuttle no longer flies, the answer itself is irrelevant to the posted question. But the information in the answer is interesting so thank you for the contribution. $\endgroup$
    – Woody
    Dec 14, 2021 at 23:12

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