10
$\begingroup$

The inclination range from KSC is advertised to be 28 to 62 degrees; what is the lowest inclination ever reached by a US crewed spacecraft?

$\endgroup$
5
  • $\begingroup$ I found the missions Gemini 9A-12 had inclinations of 28.8 degress which so far is the lowest I've seen and close to the lower limit. It's still possible that some shuttle mission had a slightly lower one. $\endgroup$ Feb 28 at 17:50
  • $\begingroup$ @OldManJohn sounds like that should be an answer. $\endgroup$ Feb 28 at 18:00
  • $\begingroup$ I dunno because I didn't check all the Space Shuttle missions. It's possible a shuttle had to set out some satellite into an even lower inclination orbit. $\endgroup$ Feb 28 at 18:12
  • 2
    $\begingroup$ Just found out STS-6 had an inclination of 28.5 degrees. $\endgroup$ Feb 28 at 18:20
  • $\begingroup$ @OldManJohn you could probably check them pretty quickly in the Shuttle Mission Summaries book ntrs.nasa.gov/api/citations/20110001406/downloads/… FWIW, I think it was 61-C at a few tenths of a degree lower than 6, but I am not sure. $\endgroup$ Feb 28 at 18:25

2 Answers 2

12
$\begingroup$

@Mark's answer hints that the Apollo mission, in particular Apollo 11, may have achieved a lower inclination. I was going to quickly query Horizons and leave a comment, but the comment space is not big enough. (See also this Q&A - the data in Horizons is in fact from the reconstruction paper by D. Adamo: "The trajectory here is a reconstruction of the Apollo 10 Lunar Module ascent stage ("Snoopy") departure trajectory developed by Daniel R. Adamo under contract to NASA in 2012.")

There is no Apollo 11 data in Horizons, but Apollo 10 was the dress rehearsal on the same trajectory. There are data in Horizons for Apollo 10 S-IVB and Apollo 10 LM in Horizons, but:

  • The available data for S-IVB spans: 1969-05-18 19:44:21.996 to 1969-05-29 00:06:39.623
  • The available data for the LM spans: 1969-05-23 05:37:54.108 to 1969-05-28 00:06:39.620

The end of the S-IVB data is more than 10 days after separation from CSM, so no longer "manned". It launched at 31.7 degrees inclination and stayed there until separation:

2440360.322476852 = A.D. 1969-May-18 19:44:22.0000 TDB 
 EC= 9.778336017523246E-01 QR= 6.600535090854220E+03 IN= 3.171696024019450E+01
 OM= 3.513742184027363E+02 W = 3.189845948237624E+02 Tp=  2440360.309970424976
 N = 2.226206763611398E-04 MA= 2.405539477034753E-01 TA= 7.412436491547562E+01
 A = 2.977721060996602E+05 AD= 5.889436771084660E+05 PR= 1.617100468314096E+06

The start of LM data is about 20 minutes after undocking from the CSM and thus also not "manned". The first data point gives an geocentric inclination of 25.8 degrees:

2440364.734664352 = A.D. 1969-May-23 05:37:55.0000 TDB 
 EC= 1.262740952534845E+01 QR= 3.946519256670695E+05 IN= 2.575192158466826E+01
 OM= 5.684924501806329E+00 W = 1.416655472146743E+02 Tp=  2440364.927556369919
 N = 5.784883680504900E-03 MA=-9.641012156494519E+01 TA= 3.510906790627678E+02
 A =-3.394151765332636E+04 AD= 9.999999999999998E+99 PR= 9.999999999999998E+99

I can't find data on the CSM, but assuming they didn't do inclination change manoeuvres, about 25.8 degrees is the lowest inclination achieved. Apollo 12 and 14 landed also close to the lunar equator (3 and 4 degrees North respectively, versus 1 degree North for Apollo 11), so it is possible, depending on the position of the Moon in its orbit, that these mission achieved lower inclinations. However, I can only find data for Apollo 12's S-IVB stage, which launched at 30.3 degrees inclination:

440540.314409271 = A.D. 1969-Nov-14 19:32:44.9610 TDB 
 EC= 9.695001248784367E-01 QR= 6.593844612331486E+03 IN= 3.028890491094399E+01
 OM= 1.593590259652690E+02 W = 1.555411939663367E+01 Tp=  2440540.300549437292
 N = 3.598574894853124E-04 MA= 4.309256118339835E-01 TA= 7.848992557793970E+01
 A = 2.161925118070309E+05 AD= 4.257911790017304E+05 PR= 1.000396019310009E+06

In summary: if I did my analysis correct, one of the Apollo missions possibly achieved the lowest inclination on return from the Moon, but only by a small margin (less than 3 degrees), with unknown error.

$\endgroup$
12
$\begingroup$

Of the missions I've been able to find orbital data for, STS 49 has the lowest inclination, at 28.32 degrees (from Space Shuttle Missions Summary). However, I haven't been able to find inclination data for the trans-Earth phase of any of the Apollo missions. Apollo 11, in particular, was in a near-equatorial orbit around the Moon, which translates into a trans-Earth inclination equal to the Moon's Earth-equatorial inclination (about 28 degrees at the time). It's possible that Apollo 11 beat the Space Shuttle's record by a bit.

$\endgroup$
1
  • $\begingroup$ Another record for STS-49! Thanks. $\endgroup$ Feb 29 at 15:26

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.