DIRECT & Jupiter Rocket Family

For a history of the proposal, see DIRECT.

For other uses, see Jupiter (rocket).

Jupiter

The Jupiter common core stage is based heavily on Space Shuttle components
Function	Manned launch vehicle
Country of origin	United States
Size
Height	70.9–92.3 m (233–303 ft)
Diameter	8.41 m (27.6 ft)
Mass	2,061,689–2,177,650 kg (4,545,246–4,800,896 lb)
Stages	1 or 2
Capacity
Payload to LEO (185 km x 51.6°)
Mass	60,282 kg (132,899 lb) (Jupiter-130)
Payload to LEO (241 km x 29°)
Mass	91,670 kg (202,100 lb) (Jupiter-246)
Associated rockets
Family	SDLV
Comparable	National Launch System
Launch history
Status	Proposed
Launch sites	LC-39, Kennedy Space Center
Type of passengers/cargo	Orion Crew Exploration Vehicle Altair Lunar Surface Access Module
Boosters – Shuttle RSRM
No. boosters	2
Powered by	1 solid
Maximum thrust	12,868–13,977 kN (2,893,000–3,142,000 lbf) (sea level - vacuum)
Total thrust	25,737–27,955 kN (5,786,000–6,285,000 lbf) (sea level - vacuum)
Specific impulse	237.0 - 269.1 sec (sea level - vacuum)
Burn time	123.8 sec
Propellant	APCP/PBAN
First stage (Jupiter-130) – Common core stage
Diameter	8.41 m (27.6 ft)
Powered by	3 SSME-Block-II
Maximum thrust	5,235–6,550 kN (1,177,000–1,472,000 lbf) (sea level - vacuum; three engines combined)
Specific impulse	361.4 - 452.2 sec (sea level - vacuum)
Burn time	524.5 sec
Propellant	LOX/LH2
First stage (Jupiter-246) – Common core stage
Diameter	8.41 m (27.6 ft)
Powered by	4 SSME-Block-II
Maximum thrust	6,981–8,734 kN (1,569,000–1,963,000 lbf) (sea level - vacuum)
Specific impulse	361.4 (SL) 452.2 sec (sea level - vacuum)
Burn time	384.1 sec
Propellant	LOX/LH2
Second stage (Jupiter-246) – Jupiter Upper Stage
Diameter	8.41 m (27.6 ft)
Powered by	6 RL10B-2
Maximum thrust	661 kN (149,000 lbf) (vacuum)
Specific impulse	459 sec (vacuum)
Burn time	609.9 sec
Propellant	LOX/LH2

The Jupiter family of rockets is part of a the proposed DIRECT Shuttle-Derived Launch Vehicle architecture, which is intended to be an alternative to the Ares I and Ares V rockets which are currently under construction for the United States National Aeronautics and Space Administration's Project Constellation. It is intended to re-use as much hardware and facilities from the Space Shuttle program as possible.

DIRECT proposal

Main article: DIRECT

Some envisioned Jupiter configurations, including crew and cargo variants

Jupiter was designed to be a high-commonality family of rockets, adapted closely from existing Space Shuttle systems. Each Jupiter launch vehicle would use a "common core stage" consisting of a tank structure based closely on the existing Space Shuttle External Tank with a pair of standard four-segment Solid Rocket Boosters (SRBs) mounted at the sides as on the Space Shuttle. Up to four Space Shuttle Main Engines (SSMEs) from the Space Shuttle Orbiter would be attached to the bottom of the tank and would be deorbited to burn up in Earth atmosphere along with the expended tank. For heavier payloads a proposed Jupiter Upper Stage (JUS) would be added atop the tank structure. For extra-planetary expeditions, the JUS would serve in a role similar to the Earth Departure Stage planned for Ares V. DIRECT have purposefully specified existing components for their launch vehicles, but contend that they could incorporate improvements such as the more powerful five-segment SRB and J-2X upper stage engine currently under development for the Constellation Program should they became available.

Crews would be carried atop the launch vehicle in NASA's planned Orion Crew Exploration Vehicle, itself topped by the planned Launch Abort System. Cargo, whether carried under Orion or alone on a cargo-only launch would be enclosed by a payload fairing.

Variants

Many configurations of Jupiter are possible, but the DIRECT version 3.0 proposal, released in May 2009, recommends two: the Jupiter-130 and Jupiter-246, with claimed lift capacities exceeding 60 and 90 tonnes, respectively, to low Earth orbit..

Jupiter-130

DIRECT proposes that its smaller Jupiter-130 be the first configuration developed, with the goal of becoming operational within four years of the start of the development program. The Jupiter-130 would consist of the Jupiter common core stage alone, fitted with one SSME removed and a payload fairing on top. "130" stands for one cryogenic core stage, three main engines, and zero upper-stage engines. Initial launches would rotate crews and bring cargo to the International Space Station, a function currently carried out by Soyuz rockets and the soon-to-be-retired Space Shuttle.

DIRECT calculations indicate that the Jupiter-130 should be able to deliver between over 60 t and over 70 t of cargo or cargo and crew to a variety of circular and elliptical inclined low Earth orbits. When the mass of the proposed Orion spacecraft and crew is subtracted (18 - 22 t depending on the mission), the remainder compares favorably with the approximately 25 t cargo capacity of the Space Shuttle, and the lack of capacity of Ares I besides the Orion spacecraft.

Jupiter-246

The Jupiter-246 would use four Space Shuttle Main Engines (SSMEs) in the common core stage and would include a planned upper stage, informally called the Jupiter Upper Stage (JUS). Apart from fourth SSME added, core stage is the same as one used by Jupiter-130. The Jupiter-246 would use six RL10B-2 engines on the upper stage. The primary role for the Jupiter-246 would be to launch heavier cargo as well as crew and cargo for lunar missions.

Jupiter Upper Stage

Because the Jupiter-246 uses four SSMEs on the core stage, the core stage propellant is depleted before it reaches low Earth orbit, and a large capacity upper stage is used to put payload to orbit. Launched with a partial upper stage propellant load of 75 t, a Jupiter-246 could deliver over 84 t of crew and cargo to a circular 241 km (130 nmi), 29° inclined orbit. On a launch with no crew or payload, the same 75 t of propellant could deliver an additional 100 t of propellant to the same orbit. For that reason, the total JUS capacity is approximately 175 t. For lunar missions where the JUS is to serve as the Earth departure stage, a full load of 175 t of propellant would be launched and 75 t would be consumed in achieving low Earth orbit, leaving 100 t available for the Earth departure burn.

In line with the DIRECT v3.0 theme of using as much existing hardware as possible, DIRECT proposes the veteran RL10 engine family to power the JUS. However, DIRECT anticipates similar performance for its upper stage from the J-2X engine, currently under development for the Ares I and Ares V upper stages, were it to become available.

Design Considerations

Expanded diagram of the DIRECT v3.0 Jupiter-130 configuration

Integrated Approach

According to the DIRECT team, many NASA engineers and managers have supported the concept and have completed a cost analysis comparison with NASA's current Constellation program and a detailed series of evaluations for supporting facilities such as data on the existing manufacturing facilities for the External Tank at the Michoud Assembly Facility and the various launch-processing facilities currently at the Kennedy Space Center. The DIRECT proposal wants to re-use almost all of the existing facilities. In contrast Ares I and Ares V will require extensive modifications and replacements over the existing facilities currently in use.

The DIRECT's Core Stage would use the existing 8.41m diameter of the Shuttle's External Tank. Ares V on the other hand is designed for a new 10.06m diameter Core Stage. The DIRECT team claims that due to not increasing the core stage's diameter the existing manufacturing tooling for the External Tank at the Michoud Assembly Facility, the existing Pegasus barge used to transport the tank from Michoud to Kennedy Space Center, the existing work platforms in the Vehicle Assembly Building, the existing Mobile Launcher Platforms and Crawler-Transporters, and parts of the structure of the existing Fixed Service Structure and Flame Trenches at Launch Complex 39 could be used without major modifications.

Existing Engine Use

One of the primary goals of the DIRECT proposal is to develop a new heavy lift rocket in a shorter timeframe. As a consequence, the proposal states that Jupiter-130 would use the four-segment Solid Rocket Boosters (SRBs) currently flown on the Space Shuttle. The Space Shuttle Main Engines attached to the bottom of the tank are identical to those of the Space Shuttle orbiter, however will not be reusable. The upper stage for missions beyond lower Earth orbit would use six RL-10B-2 engines. The SSME and RL-10B-2 engines both have long flight histories. NASA's Ares I rocket requires a new, modified five-segment version of the Space Shuttle SRBs, and a modification of the J-2 engine used for the Saturn V, the J-2X engine, for its upper stage.

Crew Safety

DIRECT envisions continued development and operation of NASA's Orion crewed spacecraft, including its Launch Abort System (LAS). In the event of an emergency, the LAS would pull the crew capsule to safety as it would on NASA's Ares I. The DIRECT Team asserts, however, that the Jupiter-130's greater lift capacity - 64 tonnes, versus 25 tonnes for Ares I - would enable the Orion to be designed with more crew safety capability than currently planned, at least from a launch-capacity standpoint.

For crewed flights to the International Space Station (ISS), DIRECT says the added lift capacity of the Jupiter would allow these missions to carry significant cargo in a separate module mounted below the Orion spacecraft. In this plan, once orbit was reached, the Orion would dock with this module and ferry it to the ISS. By comparison, Ares I would be capable of bringing only the Orion spacecraft to the ISS. DIRECT asserts that flying Orion and a separate payload module on a Jupiter would satisfy the safety concerns raised about flying crew separately from cargo following the 2003 Space Shuttle Columbia disaster, since the Orion capsule would still be able to separate from the launch vehicle and any cargo in the event of a launch abort.

Jupiter vs. Ares I

The DIRECT Team cites a number of particular features that it says would make a Jupiter-130 safer than the Ares I:

• The Jupiter design would re-use the proven method of Space Shuttle of attaching the SRBs to the tankage though an internal structural member. DIRECT says this would avoid the inducing of potentially severe vibration in the vehicle, resulting from a "thrust oscillation" effect endemic in large solid rockets. This effect has become a concern for the Ares I design.

• As with the Space Shuttle, the liquid main engines of a Jupiter-130 would be ignited on the ground and undergo a rapid checkout before the SRBs are ignited and the vehicle is launched. Start-sequence problems could be detected before committing to the launch, and the only vehicle staging event would be the burnout and separation of the SRBs. By comparison, the Ares I launch consists of the immediate ignition of its single SRB first stage, then requires a staging event and ignition at altitude of its cryogenic second stage. While staging is common launch vehicle practice, it introduces safety, risk and reliability concerns, particularly on crewed flights. (The larger Jupiter-246, with its upper stage, would typically include this risk.)

• The DIRECT Team asserts that the Jupiter-130 and -246, with their multiple main engines, would be capable of reaching orbit even in the event of an engine shutdown.

• In the Jupiter concept, the crewed Orion spacecraft would be supported by a large aerodynamic fairing. This arrangement would place the Orion at least 10 meters (33ft) further away from propellant-filled stages than it would be on an Ares I. DIRECT asserts this would provide a valuable additional "buffer space" between an exploding vehicle and the crew.

• The envisioned lift capacity of the Jupiter-130 could allow protective hardware to be mounted inside the payload fairing, below the Orion spacecraft. DIRECT has postulated such options as mounting a lightweight shield made from Boron carbide and Kevlar between the spacecraft and the stages below to help protect the crew from shrapnel and other debris from a vehicle explosion.

Jupiter vs. Ares V

The current baseline configuration of the Ares V heavy-lift cargo rocket employs six RS-68B main engines and two "stretched" 5.5segment SRBs. According to NASA, this vehicle design has a Loss of Mission (LOM) risk factor below 1 in 90 and a Loss of Crew (LOC) risk factor below 1 in 850.

The ESAS Report specified that an LOC of 1 in 1,000 (a figure estimated to be at least five times higher than the Space Shuttle today, even accounting for the latest safety upgrades) would be the minimum required to be acceptable for human use for any new systems, using this issue to dismiss vehicles from consideration such as the Atlas V.

The DIRECT Team asserts that, because Ares V will not meet NASA's targets regarding human safety all Ares-based missions will be forced to utilize an Ares I, incurring all of its associated costs for every mission type. However, being considerably smaller and with fewer engines, even the larger Jupiter variant, the now superseded DIRECT v2.0 Jupiter-232, was expected to comfortably exceed these targets with an LOC of 1 in 1,162. DIRECT's advocates say that, if the DIRECT v3.0 vehicles have similar safety margins, the DIRECT system could offer considerable mission flexibility. Lunar missions could be flown with a pair of powerful two-stage Jupiters instead of one single-stage crew vehicle and one two-stage cargo vehicle.

See also

• Saturn (rocket family)

External links

• DIRECT Launcher proposal website