Atlas Legacy

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:

1. Build the rocket with payload in the VAB
2. Remove the booster skirt with its engines
3. Reduce fuel in first stage until TWR is just great than 1
4. Re-attach the booster skirt and make a note of the time remaining in stage burn (e.g. 30s)
5. Refuel the tanks
6. 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

Background

Over the course of its long life, there have been many proposed Atlas designs that were never developed. Some are essentially early concepts for launch vehicles that flew many years later. Some of the more unique variants that can be built with BDB parts are listed below.

Tags: Bossart, SLV3X, CELV

Variants

Launch Vehicle	First Stage	Second Stage	Third Stage
Atlas-Vega	BMM LR89-5	Vejur	Optional JPL6K
Atlas SLV-3X	2.4m dia; H-1D	Centaur D
Atlas SLV-3XA	2.4m dia; H-1D	Agena D
Atlas SLV-3K	3m dia; 5x H-1D	Centaur D-1
Atlas II CELV	3.175m dia; 5x H-1D	Centaur G Prime

Basic Build Guide

Atlas-Vega is a variant of Atlas LV3-C with a Vega (Vejur) second stage powered by a Vanguard (Viklun) first stage engine. In the three stage variant, a JPL 6K stage taken from Juno IV (Chryslus) can be added. Vega is a drop in replacement for Centaur and uses the same interstage and fairing base under the avionics Unit.

The SLV-3X designation is reused often to refer to experimental designs. The 1970 SLV-3X is a "fat" Atlas SLV-3C with expanded 2.5m diameter (KSP Scale) first stage tanks and an H-1D sustainer engine in place of the LR105-7. A roll control system on the interstage is used in place of verniers.

SLV-3K is an even fatter Atlas with 3.125m diameter tanks boosted by 4x H-1D engines and a single H-1D sustainer topped by a Centaur D-1 and a widened fairing.

Atlas II Centaur G Prime (not to be confused with the later Atlas II that actually flew) was proposed for the USAF Complementary Expendable Launch Vehicle (CELV) competition in 1984. It features a 3.125m diameter first stage powered by 5x H-1D engines and 4x SRB's not dissimilar to the AJ-60A's used on Atlas V.