GCAT: General Catalog of Artificial Space Objects

Jonathan C. McDowell


Launch Success Fractions

The practice, of which I and others have long been guilty, of evaluating launch vehicle reliability based on a simple pass/fail value for each launch is rather a blunt instrument. To try and do a bit better, I have added a launch success fraction in some cases.

In the LaunchCode field of the launch lists, I take a rather old-fashioned view of success and failure. Nowadays, if a commercial satellite launch vehicle fails to deliver all its customer payloads to the correct orbit in working order, the launch is considered a total failure. In the 1950s, however, a US government launch that got only a few metres off the pad might still be considered a `partial success', for example because it demonstrated the correct functioning of the engine ignition system and the ability of the rocket to fly in vaguely the right direction.

When you're assessing the capability of launch vehicles over decades and comparing those from new space players and established spacefarers, this older approach is actually helpful. In 2012 I introduced the following scheme.

For pass/fail purposes I consider a score of less than 0.75 to be a failure; one could argue for lowering that boundary a little bit.

For launches with a single payload, or multiple equal-priority payloads, I give:
- full success1.00
- orbit usable but not nominal0.75
- orbit but not a usable one0.40
- payload failed to separate or fatally damaged by LV0.25(even if good orbit)
- orbit not reached0.00(or reentry after circa 1 orbit)

For missions with primary (P) and secondary (S) payloads, a rough scaling to give the P 3 times the weight of S -
- full success1.00
- S off-nominal orbit0.95
- S unusable orbit0.85
- S failed to sep0.75
- P off-nominal orbit0.55
- P unusable orbit0.30
- P failed to separate0.10

There's still some subjectivity here, and I've allowed myself to assign intermediate values, e.g. when an orbit is only slightly off-nominal. Now obviously scores of 0.40 or less are going to mean an unhappy customer, but I think it's still worth distinguishing from complete failure to orbit a it usually indicates a vehicle which is 'close' to working in contrast to some vehicles which never make it beyond first or second stage burn. In my initial implementation in 2012, the scores assigned that differ from 0.0 and 1.0 were:
ScoreLaunchCodeLaunch (Launch desig, vehicle)
0.25OF2596-061 Pegasus
0.40OF4063-021 Thor Agena, 67-032 Proton. 76-062,76-088, 80-031, 86-075,90-055 Molniya, 78-119, 95-052 Kosmos, 84-120, 04-052 Tsiklon, 91-051 Pegasus, 95-U01 Mu-3S-II, 96-048 CZ-3, 80-043 Atlas, 99-017, 99-023 Titan, 99-024 Delta 3, 06-006, 08-011, 11-045, 12-044 Proton/Briz, 11-005 Rokot
0.45OF4504-050 Delta 4H (primary payload medium-bad orbit, secondary failed to orbit)
0.50OF5001-029 Ariane 5/V142
0.75OS7597-057 PSLV, 97-066 Ariane 502, 07-027 Atlas V/NROL-30, 09-029 Soyuz/Meridian
0.80OS8000-048 Delta 3, 01-015 GSLV (somewhat off-nominal orbit)
0.85OS8512-054 Falcon 9 (primary perfect, secondary unusable)