Atlas - friznit/Unofficial-BDB-Wiki GitHub Wiki
Background
Originally designed as an ICBM, the iconic Atlas rocket (BDB Bossart) launched the first four American astronauts into orbit in Project Mercury. Atlas D derived variants have a unique stage and a half design, jettisoning the booster engines to save weight and using the sustainer engine alone to finalise orbit. As a rough guide, jettison the booster stage at 3.5 to 4Gs for earlier models. This can be done manually or with the auto jettison option in the booster skirt Part Action Window. Burn time should extend from around 30s to 2 minutes at just above 1G.
For a more precise estimate of when to stage the booster skirt for a given payload:
- Build the rocket with payload in the VAB
- Remove the booster skirt with its engines
- Reduce fuel in first stage until TWR is just great than 1
- Re-attach the booster skirt and make a note of the time remaining in stage burn (e.g. 30s)
- Refuel the tanks
- Launch and stage at the noted time remaining
Refer to Marcelo Silveira's Atlas Payload Performance graphs for further details.
Tags: Bossart
Variants
| Launch Vehicle | First Stage | Second Stage | Remarks |
|---|---|---|---|
| Atlas-Able | BMT LR89-5 | Alpha | |
| Atlas-Agena LV-3A | BMT LR89-5 | Belle A/B/D | |
| Atlas-Mercury LV-3B | BMT LR89-5 | Hermes | Use 1.25m Part Swith |
| Atlas-Centaur LV-3C | BMM LR89-5 | Inon D | |
| Atlas SLV-3 | BMT LR89-7 | Belle D | |
| Atlas SLV-3A | BMST LR89-7 | Belle D | |
| Atlas SLV-3B | BMM LR89-7 | Belle D | Agena inside 1.875m fairing |
| Atlas SLV-3C | BMM LR89-7 | Inon D | |
| Atlas SLV-3D | BMM LR89-7 | Inon D-1A | |
| Atlas E/F | BM LR89-7 | Staara-37/48B | Refurbished ICBM |
| Atlas H | BMM LR89-7 | SLV-3D first stage | |
| Atlas I | BMMS LR89-7 | Inon D-1A | |
| Atlas II | BMMM RS56-OBA | Inon II | Straight Fairing |
| Atlas IIA | BMMM RS56-OBA | Inon II | 2.5m Fairing |
| Atlas IIAS | BMMM RS56-OBA | Inon II | 4x Dioscuri-4A Dziran SRB |
| Atlas IIIA | BMMMM RD-180 | Inon II | Single Engine Centaur |
| Atlas IIIB | BMMMM RD-180 | Inon III | Dual Engine Centaur |
Basic Build Guide
Upper Stages
Belle (Agena) sees heavy use in the early days, while Inon (Centaur) is continuously upgraded alongside Atlas. Atlas-Centaur is a capable platform for moderate geostationary and interplanetary payloads.
- Alpha
- Belle
- Inon
First Stage
All stage and a half designs are built from a common set of parts. The large fuel tank is the Base(B) with an adapter tank and single sustainer engine. The booster fairing fits twin booster engines. Two "Crow" verniers go on the flat spot on side of the tank. On top of the Base goes various combinations of Medium(M), Small(S) and Tapered(T) tanks. Refer to the table above for details.
The Bossart-IE-105 "Vulture" main engine (LR-105) is optimised for vacuum and is supported by two Bossart-IE-89 "Buzzard" booster engines (LR-89). The booster engines have two upgrades representing the LR89-5, LR89-7 and RS56-OBA (available via Part Switch once the relevant tech is unlocked). Starting with Atlas III the stage and a half section is replaced by the single part RD-180 engine. The model of the RD-180 can be switched to fit either Atlas III or Atlas V.
First Generation
The first generation launch vehicles were derived from the Atlas D ICBM and used LR89-5 booster engines with a single LR105-5 sustainer. LV-3C is the original Atlas Centaur featuring the first ever liquid hydrogen upper stage. The tapered fuel tank has a variant switch to fit the Able upper stage.
LV-3A, LV-3B, and LV-3C
Second Generation
SLV-3 is the first dedicated satellite launch vehicle and included uprated LR89-7 and LR105-7 engines. Atlas G and it's similar cousin Atlas 1 flew until 1997.
SLV-3, SLV-3A, SLV-3B, SLV-3C, SLV-3D, and Atlas I
Third Generation
Developed for the USAF MLV-3 competition in 1988, Atlas II features stretched tanks on both the first stage and Centaur upper stage and uprated RS56-OBA engines. The vernier engines are removed to make room for strap on boosters and replaced by a single roll control thruster on the Centaur interstage. The boosters are ignited in pairs, with the second set staging just after the first pair burn out.
Atlas II and Atlas IIAS
Fourth Generation
After the merger of Martin Marietta and General Dynamics in 1993, the Atlas launch vehicle was simplified. The stage and a half design was replaced by a powerful RD-180 that allowed removal of one Centaur engine. With two engines available throughout the burn Atlas III does not need vernier engines or roll control thrusters.
Atlas IIIA, IIIB and Atlas V
Atlas LV3 Agena D with Mariner 3