08ICES-0046 Testing the Celentano Curve: An Empirical Survey of Predictions for Human Spacecraft Pressurized Volume
In 1963, Celentano, Amorelli, and Freeman published a set of curves that predicted the amount of pressurized volume per crew member to conduct a space mission at three levels of accommodation: “tolerable, performance, optima.” Since this seminal paper, habitability researchers and organizations have published more than a dozen interpretations and variations of the Celentano curves. This paper presents an analysis of the Celentano hypothesis, and its acolytes, testing them against the historical and empirical data or human spaceflight.
In each case, the authors frame their predictions in terms of “meeting crew needs.” Most notable among these predictions of volumetric “requirements,” NASA adopted an embodiment of the Celentano curve in the 1987 and 1995 editions of NASA Standard 3000 (Man-System Integration Standard).
Since Yuri Gagarin flew in Voskhod in 1961, space agencies have launched over 250 human spaceflights. These spaceflights -- from the earliest flights in tiny Mercury capsules to the capacious International Space Station -- provide the baseline from which to evaluate and test this long-accepted set of predictions. But first a caveat: it is possible to assert that the spacecraft volume met crew needs only insofar as none of them became sick, performed inadequately, or died from the cause of insufficient volume. What the historical record affords is a metric to analyze how pressurized volume varies with mission duration.
FIGURE 1 shows the original Celentano plot that features the volume prediction rising steeply over the shorter missions, but leveling out at about six months. Celentano, Amorelli and Freeman posited three levels of accommodation “tolerable, performance, and optimal,” but did not define them clearly.
FIGURE 2 shows the NASA Standard 3000 interpretation of the Celentano curves, with all three levels of accommodation passing through the origin (no crew time-no volume?). FIGURE 3 shows the complete historic spaceflight data set for all spaceflights through 2006.
FIGURE 4 shows the plot of the empirical and historical record for the mission duration maxima of each spacecraft type for each size crew that flew in it, plus the future CEV and Lunar Lander crew modules.
This analysis shows that pressurized volume increases as both a power curve and a logarithmic curve with a coefficient of determination (R2 value) of 72 percent and 60 percent respectively. Within the historic envelope of spaceflight experience of over a year in space, the volume trend does not level off but continues to rise. FIGURE 1. The original “Celentano Curve” 1963 showing Volume in ft^3 on the Y-axis and Mission Duration in months on the X-Axis. The three curves are labeled from top to bottom as “Optimal, Performance, and Tolerable.” FIGURE 2. NASA Standard 3000, Man-System Integration Standard, Figure 8.6.2.1-1. Guideline for determination of total habitable volume per person in the space module. FIGURE 3. Logarithmic graph of the historic record of 256 spaceflights through 2006.
Salyut Missions Testing the Celentano Curve: Spaceflight Mission Series Mir Missions 1000.00 Skylab Missions Mercury Missions Gemini Missions Apollo Missions Apollo-Soyuz Test Project Space Shuttle Only Missions ISS Expeditions Shuttle-Spacelab Missions
M^3 100.00 Shuttle-SpaceHab in Shuttle-Mir Missions Vostok-Voskhod Missions Soyuz Missions Member All Shuttle Missions Shenzhou Crew Power (Skylab Missions) per Power (Shuttle-SpaceHab) 10.00 Log. (Salyut Missions) Log. (Mir Missions) Volume Power (ISS Expeditions) Log. (Apollo Missions) Log. (Mercury Missions) Log. (Gemini Missions) Log. (Vostok-Voskhod Missions) Log. (Space Shuttle Only Missions) 1.00 Power (Soyuz Missions) 0.10 1.00 10.00 100.00 1000.00 Log. (Shuttle-Mir Missions) Duration in Days Log. (Shuttle-SpaceHab) Power (Shenzhou) FIGURE 4. Historic and empirical record: the volume per crew member versus mission duration for crewed spacecraft maxima for mission duration for every crew size in each spacecraft configuration.
Pressurized Volume Per Crew Member Versus Mission Duration for Crewed Spacecraft Unique Data Points: Maxima for Mission Durations for Every Crew Size in Each Spacecraft Configuration 1000
ISS Expd. 10 m^3
in Mir EO19 ISS Expd. 8 Mir EO9/10, LD3 Skylab 4 ISS Expd. 4 Mir EO 26/27, Perseus 100 Salyut 7 EO5/Kosmos 1443 Mir EO5 Mir EO20/Euromir 95 ISS Expd. 1 Mir EO15/16, LD4 Salyut 7 EO4-2/Kosmos 1443 Mir EO4/LD2 Mir EO3 Salyut 4 (Almaz) Salyut 6 STS-73/USML2 Salyut 7 EO1 Crewmember Mir EO1 STS-9/SL1 Salyut 1 Salyut 7 EO3
per STS-61A SL D1 STS-78 LMSL STS-107 SH DM STS-77 SH-5 SM STS-111 STS-95 SH 6 SM STS-80 Volume STS-59 10 Shenzhou 6 STS-67 NGB Lunar Lander ESAS Lunar Lander Soyuz 9 Vostok 5 Apollo 12 ASTP CEV 701 w/ 4 Crew
Pressurized Soyuz 7 Apollo 17 LM Apollo 8 Voskhod 2 CEV 701 w/6 Crew y = 1.74x0.7444 Mercury 8 R 2 = 0.7221 Gemini 6 1 1 y = 23.782Ln(x) - 34.708 10 100 Dup ASTP 1000 R 2 = 0.6047 Mission Duration in Days