Delta Numbering System
In 1972, McDonnell Douglas introduced a four-digit numbering system to replace the letter-naming system.
The new system could better accommodate the various changes and improvements to Delta rockets (and avoided the problem of a rapidly depleting alphabet).
It specified (1) the tank and main engine type, (2) number of solid boosters, (3) second stage (letters refer to engine, not earlier letter system), and (4) third stage.
| Number | First Digit (First stage/boosters) |
Second Digit (Number of boosters) |
Third Digit (Second Stage) |
Fourth Digit (Third stage) |
Letter (Heavy configuration) |
|---|---|---|---|---|---|
| 0 | Long Tank Thor MB-3 engine Castor 2 SRBs |
No SRBs | Delta F*, with Aerojet AJ-10-118F engines. *References uprated Aerojet AJ-10-118 engine |
No third stage | N/A |
| 1 | Extended Long Tank Thor MB-3 engine Castor 2 SRBs |
N/A | Delta P*, Douglas built with TRW TR-201 engines. *Exception: AJ-10-118F engine for Anik-A1 launch. |
N/A | |
| 2 | Extended Long Tank Thor RS-27 engine Castor 2 SRBs |
2 SRBs (or LRBs in the case of the Delta IVH) | Delta K*, with AJ-10-118K engines. *References uprated Aerojet AJ-10-118 engine |
FW-4D (unflown) | |
| 3 | Extended Long Tank Thor RS-27 engine Castor 4 SRBs |
3 SRBs | Delta III cryogenic upper stage, RL-10B-2 engine | Star 37D | |
| 4 | Extended Long Tank Thor MB-3 engine Castor 4A SRBs |
4 SRBs | Delta IV 4m diameter cryogenic upper stage, RL-10B-2 engine | Star 37E | |
| 5 | Extended Long Tank Thor RS-27 engine Castor 4A SRBs |
N/A | Delta IV 5m diameter cryogenic upper stage, RL-10B-2 engine | Star 48B/PAM-D | |
| 6 | Extra-Extended Long Tank Thor RS-27 engine Castor 4A SRBs |
6 SRBs | N/A | Star 37FM | |
| 7 | Extra-Extended Long Tank Thor RS-27A engine GEM 40 SRBs |
N/A | N/A | GEM 46 SRBs | |
| 8 | Strengthened Extra-Extended Long Tank Thor RS-27A engine GEM 46 SRBs |
N/A | |||
| 9 | Delta IV CBC RS-68 engine |
9 SRBs | 2 additional CBC Parallel first stages |
This numbering system was to have been phased out in favor of a new system that was introduced in 2005. In practice, this system was never been used.
| Number | First Digit (First stage/boosters) |
Second Digit (Number of boosters) |
Third Digit (Second Stage) |
Fourth Digit (Third stage) |
Letter (Heavy configuration) |
|---|---|---|---|---|---|
| 0 | N/A | No SRBs | N/A | No third stage | N/A |
| 1 | N/A | N/A | |||
| 2 | Extra-Extended Long Tank Thor RS-27A engine GEM 40 SRBs |
2 SRBs (or LRBs in the case of the Delta IVH) | Delta K, with AJ-10-118K engines | GEM 46 SRBs | |
| 3 | Strengthened Extra-Extended Long Tank Thor RS-27A engine GEM 46 SRBs |
3 SRBs | N/A | ||
| 4 | Delta IV CBC RS-68 engine |
4 SRBs | Delta IV 4m diameter cryogenic upper stage, RL-10B-2 engine | 2 additional CBC Parallel first stages | |
| 5 | N/A | N/A | Delta IV 5m diameter cryogenic upper stage, RL-10B-2 engine | Star 48B/PAM-D | N/A |
| 6 | N/A | Star 37FM | |||
| 7 | N/A | ||||
| 8 | |||||
| 9 | 9 SRBs |
Read more about this topic: Delta (rocket Family)
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