The Human Population of Space

… is currently about six.   That is, if one adds up all the person-years spent in space by various crews, it comes to about six for recent years.  In a previous post from 2010, “The Population of Space”,  I had been wondering how much time people have actually spent in outer space.  I found that no one seems to have added it up.   So I put together a single list of all the manned space missions using the  Wikipedia article List of Human Spaceflights and merged it with Robert Braeunig’s page Manned Space Flights.  From that I was able to generate a list of all the people who have visited space and long they spent on each trip.  The results are in the tabs of this spreadsheet, Manned Spaceflight Statistics.  From there I was able to boil down the numbers to the charts below.

Here is the time spent in space by year and station:

manned_person_years The ISS dominates recent years, of course, but there was a surprising amount of time spent on Shuttle missions in the 1990s, largely because the Shuttle could carry so many people, 7, compared to any other craft.

Here are the number of visitors each year:

manned_visitorsThe numbers have dropped a lot in recent years with the retirement of the Shuttle in 2011.  Only about 12 people are going up to the ISS every year, but they’re staying for a lot longer.

The stations are:

  • Skylab: a big station put up with the last flight of a Saturn 5
  • Salyut 1-7: a series of small stations put up by the Soviets
  • Mir: A large station put up by the Soviets and occupied for 14 years
  • non-ISS Shuttle: Missions by one of the 5 US Space Shuttles.  In the 2000s the Shuttle has been almost entirely used for building the ISS, so I’ve counted  those flights in the ISS category
  • ISS: The International Space Station, a gigantic station with contributions from the US, Russia, EU, Japan, and Canada.  It’s probably the most expensive single object ever built, with a total cost of somewhere near $160 billion.   That represents about $2 billion per person-year.
  • Tiangong 1: a small station launched by China in 2011, the first in a future series.
  • Other: all the other various launches, including the suborbital ones by the X-15 and SpaceshipOne, which qualify by getting above 100 km.

Here are some stats by station:

Station Mass (tonne) Pressurized Volume (m³) First occupied Last occupied Number Flights Number visitors Total Person-years
Non Station NA NA 1961 2008 61 117 2.97
Skylab 77 320 1973 1974 3 9 1.41
Salyut 1-7 20 (for 7) 90 (for 7) 1971 1986 37 84 9.76
Mir 130 350 1986 2000 30 80 30.56
non-ISS Shuttle 68 74 1981 2009 98 575 16.79
ISS 420 916 1998 2015 81 373 67.55
Tiangong 9 15 2012 2013 2 6 0.22
Total 724 1765 1961 2015 312 1244 129.26

The ISS has more mass, volume, and person-years than all the other stations combined.

Overall, there have been 312 manned space flights carrying 1244 visitors, of whom about 2/3 (817) flew on the Shuttle.    This represents 559 individuals.   The majority of them have flown more than once.   The number of flights per person looks like this:

Number of Flights 1 2 3 4 5 6 7
By This Number of People 212 153 95 65 25 7 2

The two people with 7 flights are Franklin Chang-Diaz and Jerry Ross.

32 people have spent more than a year in space.  The top five are:

Name Number of Flights Total years in space Last there
Gennadi Padalka 5 2.41 12-Sep-15
Sergei Krikalyov 6 2.20 11-Oct-05
Aleksandr Kaleri 5 2.11 16-Mar-11
Sergei Avdeyev 3 2.05 28-Aug-99
Valeri Polyakov 2 1.86 22-Mar-95

These 5 guys represent only 1% of all astronauts, but 8% of the total person-years in space.

There have been 7 space tourists, in the sense of people who paid personally for a trip, or 10 if you also count Senators Jake Garn (flew in 1985), Bill Nelson (1985) and John Glenn (1998), who finagled trips on the Shuttle.  Charles Simonyi, a Microsoft exec, went twice.   The last tourist was in 2009, so that era may be over.  Glenn was also the oldest person ever to visit space, at 77.   Gherman Titov was the youngest at 25 in Vostok 2 in 1961.

The overall total time spent in space has been declining slightly in recent years, and the number of visitors is way off.   This is again largely because of the retirement of the Shuttle.  Also, the only manned craft currently able to reach the ISS is the Soyuz, but others are under development.   Traffic may pick up if the Chinese ramp up their own stations.  The ISS is due to be maintained until at least 2020, and probably 2024.  After that pieces of it are likely to be used in the next station.   Maybe that will be the one used when assembling the Moon and Mars missions of the 2030s.

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