Bossart IIAS
by gc1ceo
uploaded 2019-02-09
mod ship
#manned #atlas #bossart #centaur #inon


  • Type: VAB
  • Class: ship
  • Part Count: 49
  • Mods: 3


  • Bluedog DB
  • Squad (stock)
  • TweakableEverything

The Atlas rocket family began in 1959 with the launching of the first Atlas launch vehicle and within just a couple of years had become the primary heavy lifter for the American space program. The first generation of Atlas rockets were responsible for launching many important payloads both into orbit including most of the Mercury program, as well as landing the first soft-landing of an American probe on the lunar surface.

The powerful Centaur upper stage was initially developed exclusively for the Atlas rocket as it used many of the same technologies including its stainless steel extremely thin balloon tanks allowing for a high ratio between wet and dry mass. It was first used towards the end of the first generation of Atlas and continued as a successful combination into Atlas’ second generation which saw lengthened fuel tanks, improved avionics and bolder interplanetary missions.

The third generation of Atlas-Centaur rockets successfully launched both government and civilian payloads from 1984 until the Atlas G/H was last flown in 1989 after which it was re-branded as the Atlas I and successfully flew between 1990 and 1997 with civilian payloads.

The success of the Atlas I overlapped with a further development, the Atlas II, which made a couple of the Atlas design. The most noticeable was the removal of the venerable vernier engines which had been used for roll control since 1958. It was replaced with a small monopropellent roll control unit which was mounted on the interstage fairing. The Atlas engines were also replaced with two variances on a single engine thus modernizing and simplifying them while keeping the same payload capabilities. The original Atlas II flew from 1992 to 1998 and overlapped with the Atlas I after which its two variants, the IIA and IIAS, flew until 2002 and 2004 respectively.

The Atlas IIAS has two chief differences – the use of a larger payload fairing and the addition of (4) Dziran solid boosters which allows for much greater range and payload capability.

The Bossart II is Bluedog Design Bureau’s version of the Atlas II and has a number of key differences from my previous Bossart builds. The first and most obvious is the removal of the vernier rockets and addition of a single roll control unit on the interstage adapter. This has the side effect of reducing the thrust just a bit at launch but can also extend the burn time by a small amount. This can have the effect of a lower thrust-to-weight ratio (TWR) and may require some adjustments to the fuel tanks to achieve an initial positive TWR. The stage-and-a-half design still operates normally with the booster stage ejected somewhere in the upper atmosphere.

The Inon II is Bluedog Design Bureau’s version of the upgraded Centaur II with an upgraded and larger fuel tank compared to the Inon D. It is meant to carry large payloads to KSO (Kerbal Synchronous Orbit) or beyond. It still uses cryogenic fuels so depending on your setting you may experience boil-off – it isn’t meant to sit around for very long between burns.

The ascent procedure can vary depending on the mission and is a bit different whatever you are looking for a parking orbit, transfer orbit, or a direct ascent. The sustainer, booster engines, and one pair of solid boosters are fired together at launch. The first pair of solid boosters are ejected along with the second pair of solid boosters firing to keep up the thrust. Once the solid boosters have been depleted and ejected it continues it ascent much like other Bossart designs.

The booster engine skirt should be decoupled as early as when the rockets enters the upper atmosphere or as late as 30 seconds before the burn is complete. The Bossart either burns to exhaustion for a higher orbit or direct ascent or is prematurely shutdown upon reaching your parking orbit altitude.

A parking or lower orbit will probably leave you with enough fuel to complete the orbital process, or at least complete most of it thus leaving the Bossart as orbital debris. A higher or transit orbit will probably see it exhausted in which case the depleted Bossart will eventually re-enter the atmosphere. A direct ascent will see it put into a highly elliptical orbit or a crash trajectory with your target body.

The Inon D will either be used to continue a direct ascent, help to establish a parking orbit, or circularize a transit orbit. There is more than enough fuel to complete most missions and will probably be in excess in the majority of cases.

I have included a test payload, a 2 tonne keosynchronous communications satellite meant for a launch to KTO (Kerbin Transit Orbit) at 2,863.33 km meant to be a third or fourth generation communications relay. It can be substituted for any payload of roughly the same mass and dimensions.

Built in the VAB in KSP version 1.6.1.

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