KerbalX

Details

• Type: VAB
• Class: ship
• Part Count: 47
• Mods: 2
• KSP: 1.11.1

Mods

• Bluedog DB
• Squad (stock)

The Atlas rocket began life as the first ICBM developed by the United States in response to the development of the R-7 Semyorka and was first launched in 1957. It had a fairly short deployment life as an ICBM since it was rendered obsolete almost from the beginning and they were taken out of service by 1965. However between 1957 and 1959 it was chosen to serve as a space launch vehicle, much like the Redstone, but with the capacity to handle larger payloads including orbital manned flights.

The development of upper stages hit some early delays with the initial plans to develop the Vega upper stage being cancelled, three separate launch attempts with the Able failing, and finally it was paired with the Agena. This first generation of Atlas rockets would largely be modified Atlas-D missiles and given the designation of LV-3-A when paired with an Agena, LV-3-B for orbital manned flights, and lastly LV-3-C for the eventual Centaur upper stage.

The success of the LV-3 series’ led to its second generation which began with standardizing the launch vehicles which had been individually tailored for their payloads in the first generation. The introduction of the SLV-3 (standardized launch vehicle) reduced costs and sped up preparation of missions by requiring each mission to conform to a single Atlas standard. The later part of the second generation which was converted decommissioned Atlas E and F missiles into launch vehicles, further upgrades with Atlas G and H, and lastly a commercial version of the Atlas G/H known as the Atlas I.

The third generation began development in 1988 by the USAF contractors as a replacement for the oft-faulty Atlas I and to handle larger DoD payloads. It would exclusively be paired with the new upgraded Centaur II as all other upper stages had since been retired. The result was the Atlas II which was first launched in 1991 and in addition to upgrades to the engines made a few other major changes. The most obvious one was the removal of the classic Vernier engines mounted above the booster skirt. This was done so that boosters could finally be added to the Atlas rocket and was replaced by a single roll control mounted on the Centaur’s interstate adapter. While the booster skirt was retained with the Atlas II the entire internal layout was changed to the MS-5A that shared, among other things, had a common gas generator.

The original Atlas II would have a flawless record of ten launches between 1991 and 1998 and were exclusively USAF/DoD payloads. The Atlas IIA, which replaced the Centaur’s engines, served as a commercial launch vehicle between 1992 and 2002 with twenty three successful launches. Lastly, the Atlas IIAS added four Castor 4A booster rockets which would drop off before jettisoning the booster skirt which also had a flawless record of thirty successful launches between 1993 and 2004.

The powerful cryogenically-fueled Centaur upper stage eventually became the exclusive upper stage for the Atlas rocket with the retirement of the last Agena upper stages. It also flew on board Titan rockets including the heavy lifter Titan IV beginning in 1989. The development of the Atlas II was paralleled by the development of Centaur II which would be exclusive to the new Atlas II (and eventually also used some with the Atlas III).

The Bossart II is an approximation of the Atlas II by Bluedog Design Bureau but is still essentially a Bossart rocket. It still retains the stage-and-a-half design and procedure to jettison the booster skirt in the upper atmosphere. The timing for the jettison can vary greatly between 20 and 45 seconds left in the burn with 20 seconds recommended for the included payload. The biggest change is the removal of the Vernier engines and replacement with a single roll control on the Inon’s interstage adapter. It operates as a RCS thruster exclusively for rolling so you need to turn on RCS to use it successfully.

The Inon II is an approximation of the Centaur II by Bluedog Design Bureau and has a longer tank and more powerful engines compared to the Inon-D. There isn’t any real change in its operation and in this build has dual engines. It still handles all the burns done in space including the rest of the ascent as well as orbital and transfer burns.

I have made a sample heliocentric payload weighing 2.5 tonnes made to showcase what the Bossart II can handle in terms of mission and payload. The mission is fairly straightforward with the Bossart used for much of the ascent and I recommend jettisoning the booster skirt at 20 seconds left in this burn. This will add about two minutes to the burn time with a significant reduction in thrust and acceleration. The Bossart should continue to handle the ascent towards escape velocity until it is exhausted at which point the Inon II will take over.

Built in the VAB in KSP version 1.11.1.