DIRECT & Jupiter Rocket Family

DIRECT proposal

In the late 2000s, a group of space enthusiasts proposed an alternative to NASA’s planned Ares I and Ares V rockets, calling their concept DIRECT. They claimed to represent a larger, anonymous team of dozens of NASA and space industry engineers who volunteered their spare time. By September 2008, the team reportedly had 69 members, with 62 being NASA engineers, contractor engineers, or managers from the Constellation Program; a few non-NASA members acted as public spokespeople.

The name DIRECT reflected a philosophy of reusing as much Space Shuttle hardware and infrastructure as possible, aiming for a seamless transition. The team argued that a family of rockets with high commonality would lower costs, reduce the gap between the Shuttle’s retirement and the first Orion flight, speed up schedules, and simplify technical requirements. Three main versions were released, the last in May 2009. On June 17, 2009, the group presented their plan to the Review of U.S. Human Space Flight Plans Committee in Washington, D.C. After President Obama signed the NASA Authorization Act of 2010, which mandated work on the Space Launch System, the DIRECT Team declared their effort successful and disbanded.

The proposal centered on a rocket family called Jupiter, closely derived from Shuttle systems. Each Jupiter vehicle would have a common core stage: a tank structure based on the Shuttle’s External Tank, flanked by two standard four-segment Solid Rocket Boosters. At the tank’s bottom, up to four Space Shuttle Main Engines from the Orbiter would be attached. These engines, along with the spent tank, would be deorbited to burn up in the atmosphere.

Origins and history

DIRECT's Jupiter vehicle would have been an in-line Space Shuttle-derived launch vehicle, a category of adaptations postulated since before the first Shuttle launch that removes the winged Orbiter, moves the liquid main engines to the bottom of the cryogenic tankage, and relocates the payload above the tankage. The first official study of the concept was conducted in 1986 by NASA's Marshall Space Flight Center after the Challenger disaster, promoted as an alternative for launching uncrewed cargo and potentially allowing a restarted lunar program, but no funds were available and the idea was shelved.

DIRECT's approach resembled the 1991 National Launch System effort proposed jointly by NASA and the Department of Defense as an alternative to the Titan IV, which used the same solid rocket boosters and modified external tank but specified four disposable Space Transportation Main Engines; Congress did not appropriate funding. NASA's Exploration Systems Architecture Study of 2005 included a similar design using three SSMEs, known as LV-24 and LV-25, but it was dismissed for insufficient lunar performance, though the concept was not considered with an Earth departure stage.

DIRECT's re-exploration of the SDLV idea began in 2006 in frustration with the high cost and delays of Ares I and worries that similar issues with Ares V might jeopardize the Constellation Program, with an additional goal of maintaining US crew launch capability with as short a gap as possible after Shuttle retirement.

Ares I/Ares V Cost and Schedule vs. DIRECT

One of the strongest programmatic criticisms of the Ares I and Ares V architecture was the high cost for developing two new launchers and operating two concurrent programs. GAO Reports to Congress noted that Ares I alone was expected to cost up to $14.4 billion to develop, and former NASA Administrator Michael D. Griffin confirmed the total cost for both launchers would be $32 billion, with Ares V more expensive than Ares I. The Ares I schedule incurred several delays; the original ESAS Report intended a crewed flight as early as mid-2011 after Shuttle retirement in 2010, but a subsequent official NASA schedule had a 65% confidence that the first crewed flight of Ares I with Orion would occur in March 2015.

Critical activities included the J-2X upper stage engine and five-segment SRB, with concerns about thrust oscillation and Orion-Ares I integration; in 2008, Lockheed Martin requested a redesign to end integration risks, though combined test results from Ares I-X and static firing indicated thrust oscillation was not critical. DIRECT contended that the requirement to develop 5-segment SRBs and the J-2X engine for Ares I to fly the first Orion was directly responsible for schedule delays and high development costs, and that all-new manufacturing at Michoud and launch facilities at Kennedy Space Center would be required.

In contrast, DIRECT proposed reusing the existing 4-segment fully human rated SRB and SSME, reusing existing manufacturing for a modified External Tank, and requiring only moderate modifications at Kennedy Space Center. DIRECT's single launch vehicle proposal was intended to remove program risks associated with possible cancellation of Ares V due to budgetary constraints.

Design considerations

The DIRECT project aimed to create a new heavy-lift rocket more quickly. When it started in 2006, the Space Shuttle was expected to fly for about four more years. The initial plan reused the Shuttle's four-segment Solid Rocket Boosters without changes and adapted work from the Constellation program, specifically the RS-68 main engine and J-2X upper stage engine. By 2009, worries emerged that the RS-68's ablative cooling could not handle the heat from the nearby boosters.

In response, DIRECT version 3.0 proposed using the more costly, regeneratively-cooled Space Shuttle Main Engine, which was reusable, but in a disposable manner. Three or four of these engines would be attached to the core tank and discarded in the atmosphere along with the tank. For flights beyond low Earth orbit, the Jupiter Upper Stage would use six Pratt and Whitney RL10B-2 engines. The Jupiter rocket family could have launched with engines already available, with the option to upgrade to a more powerful booster and the J-2X engine later.

DIRECT also planned to continue developing NASA's Orion crew capsule and its Launch Abort System. The team argued that the Jupiter-130's lift capacity of 64 tonnes, compared to Ares I's 25 tonnes, would allow Orion to include more crew safety features than originally intended.

Did You Know?

• The Jupiter-246 designation stood for two cryogenic stages, four main engines, and six upper stage engines.
• DIRECT calculations indicated the Jupiter-130 could deliver between over 60 tonnes and over 70 tonnes of cargo or cargo and crew to a variety of low Earth orbits.