DIRECT

For other uses, see Direct.

DIRECT v3.0 - Jupiter Launch Vehicle family (J-130 / J-246)

DIRECT v2.0 illustration demonstrating commonality of components
Function	Launch vehicle system proposal supporting the Vision for Space Exploration
Manufacturer	None
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	One common core stage with optional Jupiter Upper Stage (similar role to Earth Departure Stage (EDS))
Capacity
Payload to LEO
Mass	60,282 kg (132,899 lb) (J-130, 100 x 100 nmi, 51.6° inclination)
Payload to LEO
Mass	91,670 kg (202,100 lb) (J-246, 130 x 130 nmi, 29° inclination)
Associated rockets
Family	Shuttle Derived Launch Vehicle
Comparable	National Launch System
Launch history
Status	Proposal
Launch sites	LC-39, Kennedy Space Center
Total launches	0
Type of passengers/cargo	Orion Crew Exploration Vehicle Altair Lunar Surface Access Module Jupiter Upper Stage (similar to EDS)
Boosters (Jupiter) – Shuttle RSRM
No. boosters	2
Powered by	1 RSRM
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 (J-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 (J-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; four engines combined)
Specific impulse	361.4 - 452.2 sec (sea level - vacuum)
Burn time	384.1 sec
Propellant	LOX/LH2
Second stage (J-246) – Jupiter Upper Stage
Diameter	8.41 m (27.6 ft)
Powered by	6 RL10B-2
Maximum thrust	661 kN (149,000 lbf) (vacuum; six engines combined)
Specific impulse	459 sec (vacuum)
Burn time	609.9 sec
Propellant	LOX/LH2

DIRECT is a proposed alternative Shuttle-Derived Launch Vehicle (SDLV) architecture supporting NASA's Vision for Space Exploration, which would replace the planned Ares I and Ares V with a family of rockets named "Jupiter".

DIRECT is advocated by a group of space enthusiasts who claim to represent a broader team of dozens of NASA and space industry engineers who actively work on the proposal on a volunteer basis. As of September 2008, the DIRECT Team was said to consist of 69 members, 62 of whom were NASA engineers, NASA-contractor engineers, and managers from the Constellation Program volunteering their expertise in their spare time, remaining anonymous, while seven non-NASA members of the team are representing the group.

The project name "DIRECT" refers to a philosophy of maximizing re-use of hardware and facilities with more direct heritage to those of today's Space Shuttle. The DIRECT Team asserts that using this approach to develop and operate a family of high-commonality rockets would reduce costs, shorten schedules, and simplify technical requirements for future US human space efforts.

Three major versions of the DIRECT proposal have been released with the latest, Version 3.0, having been unveiled in May 2009. On 17 June 2009, the group presented its proposal at a public hearing of the Review of U.S. Human Space Flight Plans Committee, a panel reviewing US space efforts, in Washington, D.C.

Jupiter launch vehicle family

Some envisioned Jupiter configurations, including crew and cargo variants

DIRECT advocates developing a single, high-commonality family of rockets named Jupiter, 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 (4) 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 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 the core stage, but contend that they could incorporate improvements such as the more powerful five-segment SRB currently under development for Ares I if they became available.

Crews would be carried atop the launch vehicle in NASA's the 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.

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

Jupiter-130

DIRECT proposes that its smaller J-130 be the first configuration developed, with the goal of becoming operational within four years of the start of the development program. The J-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 (1) cryogenic core stage, three (3) main engines, and zero (0) 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 J-130 should be able to deliver between over 60 t and over 70 t of crew, cargo, or mixed payloads to a wide 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 J-246 would use all four Space Shuttle Main Engines (SSMEs) and include a planned upper stage, informally called the Jupiter Upper Stage (JUS) to distinguish it from the similar but much heavier planned Ares V Earth Departure Stage. The J-246 would consist of two (2) cryogenic stages, four (4) core-stage SSME engines, and six (6) upper-stage RL10B-2 engines. The primary role for the J-246 would be to launch heavier cargo as well as crew and cargo for lunar missions.

Jupiter upper stage

Because the J-246 uses four SSMEs on a tank structure originally designed for three, the core stage propellant is depleted relatively early, and a large capacity upper stage is required. Launched with a partial upper stage propellant load of 75 t, a J-246 could deliver over 84 t of crew and cargo to a 130 nmi circular 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.

Planned and possible missions

Low Earth orbit and unmanned scientific missions

Orion spacecraft taking a Space Shuttle Payload Delivery Module (SSPDM) to the ISS, carrying an airlock, the Alpha Magnetic Spectrometer and other cargo on a single Jupiter-130.

The 20 t of extra payload capability of the Jupiter-130 would allow for a range of additional cargo payloads to be flown with each Orion crew, a capability which is not possible with the Ares I. The DIRECT Team have suggested a number of extra missions which would be enabled by Jupiter in their proposal, including:-

• New ISS resupply missions with the three ESA/ASI-built Multi-Purpose Logistics Modules
• Performing more Hubble Space Telescope Servicing Missions with Orion crews
• Launching massive new space telescopes over 8 meters in diameter (twice the diameter of Hubble)
• Perform a Mars Sample Return mission mission on a single Jupiter launcher, to land on Mars and return a sample of its soil back to Earth for study as early as 2013
• Launching a human crew to fly around the moon as early as 2013

The DIRECT team asserts that these additional new missions can be planned and funded due to development cost savings with the Jupiter rocket family compared to the current NASA baseline. The proposed new missions and payloads could providing useful employment for many people currently working in the Space Shuttle Program, which is scheduled to end in 2010.

Lunar mission architecture

As with the Ares I and Ares V, the DIRECT Team advocates the use of its Jupiter launchers for a variety of missions, including ISS crew rotation and cargo resupply, and the launch of heavy satellites and robotic exploration missions. However, a chief intent would be to use Jupiter to send astronauts to the Moon.

The baseline lunar mission approach for DIRECT Version 3.0 is similar to that for NASA's Constellation Program. Two launches would be performed for each lunar mission. One Jupiter rocket would carry the crew in NASA's planned Orion Crew Excursion Vehicle along with NASA's planned Altair Lunar Surface Access Module lunar lander to meet up with the other Jupiter, carrying only the Jupiter Upper Stage to be used as the Earth Departure Stage (EDS). The assembled Orion/Altair/EDS would leave Earth orbit for the Moon. The EDS would be expended, the spacecraft would enter lunar orbit, and the entire crew would descend to the Moon in the Altair while the Orion remained in lunar orbit.

Following surface exploration, the crew would fly a section of the Altair (the ascent stage) back to the Orion, discard the ascent stage, and put the Orion on a return trajectory to Earth. Before reentry, the Orion would discard its service module, and the crew would reenter and land in the Orion capsule.

In its various versions and literature, the DIRECT Team has postulated other mission architectures, for example using Lagrangian points in the Earth-Moon system as staging sites, as well as developing cryogenic propellant depots in low Earth orbit, to allow spacecraft to re-fuel in space and thus extend their range and capability. However, the primary DIRECT architecture intentionally matches that of NASA's.

Origins and history

1978 image of a Morton Thiokol-proposed In-Line Shuttle Derived Launch Vehicle. Note white tankage

DIRECT's Jupiter vehicle is an "in-line" Shuttle-derived launch vehicle (SDLV) concept, in contrast to the Space Shuttle where the Space Shuttle Orbiter is mounted on the side of the rocket. This broad category of Shuttle adaptations, postulated since before the first Shuttle launch, removes the winged Space Shuttle Orbiter, moves the liquid main engines to the bottom of the cryogenic tankage (typically proposed to be adapted from the Shuttle External Tank), and relocates the payload to above the tankage.

The first official study of the concept was conducted in 1986 by NASA's Marshall Space Flight Center in the aftermath of the Space Shuttle Challenger disaster. It was promoted as one of the alternatives for launching unmanned cargo and would have potentially allowed a re-started lunar program as well. There were, however, no funds available to NASA for building any new vehicles while the Space Shuttle Program continued. The idea was shelved and NASA concentrated on fixing and operating the Space Shuttle instead.

DIRECT has a resemblance to the 1991 National Launch System effort. Proposed jointly by NASA and the Department of Defense as an alternative to the Titan IV, the design was based on the same Solid Rocket Boosters and modified External Tank, but instead of the reusable Space Shuttle Main Engine, specifed four of the proposed disposable, less expensive Space Transportation Main Engines. The United States Congress did not appropriate funding for the development. A great deal of reference material exists in the public domain regarding NLS.

NASA's Exploration Systems Architecture Study (ESAS) of 2005 included a similar design to the DIRECT proposal using three Space Shuttle Main Engines (SSME). Known as LV-24 in Crew launch form, and LV-25 in Cargo configuration, the idea was dismissed because it did not have sufficient performance for the proposed lunar program - however the concept was not considered using an Earth departure stage (EDS).

DIRECT's re-exploration of the SDLV idea began in 2006 in frustration of the high cost and delays of Ares I and worries that any similar issues with the giant Ares V might put the whole Constellation Program in jeopardy. An additional goal was to maintain American ability to launch crews to space with as short a gap as possible after the planned retirement of Shuttle.

DIRECT v1.0

According to the DIRECT team, the first version of the DIRECT proposal was the product of a three-month study produced by more than a dozen NASA engineers and managers working in their free time, and a small group of engineers and non-engineers outside of NASA. DIRECT took the final ESAS recommendation of using the EDS during the ascent phase of the flight to gain additional launch performance on the Cargo LV, and applied this same methodology to the LV-24/25.

The next change in DIRECT's development was in response to NASA dropping the Space Shuttle Main Engine on the Ares V design due to the high manufacturing cost of the SSME engines and the difficulty in producing the required number of units per year with existing manufacturing facilities. NASA specified five RS-68 engines as the core engines for Ares V. The DIRECT proposal specified that it's core should include two RS-68 engines. Additional performance for carrying payloads to Low Earth Orbit would be provided by upgrading the main engines with Regenerative Cooling Nozzles to improve their efficiency.

The v1.0 proposal was submitted on October 25 2006 to NASA's Administrator, Michael D. Griffin, and a wide range of industry, political and advocacy groups involved in the Constellation program.

Criticism of v1.0

In late 2006, head of the ESAS Study, Dr. Doug Stanley, declared that the DIRECT v1.0 proposal could not work as it relied on overly-optimistic and speculative performance specifications for an upgraded RS-68 Regen engine. Dr. Stanley produced official specifications from Rocketdyne about the RS-68 Regen upgrades to prove his point.

DIRECT v2.0

Direct v2.0 proposed to human rate the RS-68 engine

On May 10 2007, a revised DIRECT proposal was released. To address criticism of relying on engine studies rather than working engines, DIRECT v2.0 specified human-rating the standard performance RS-68 as used on existing Delta IV launchers and for the upper stage chose the lower of two specifications of J-2X engine which Rocketdyne is currently developing for NASA's Ares launchers. DIRECT v2.0 introduced a scalable, modular family of Shuttle-derived launch vehicles, starting with the Jupiter-120 and Jupiter-232.

According to the proposal, the single-stage J-120 could achieve low Earth orbit with two standard ablative RS-68 engines, while an extra RS-68 was required on the core stage of the heavier two-stage J-232. The Earth Departure Stage for J-232 now required two standard J-2X engines instead of one.

The DIRECT Team produced a 131-page DIRECT v2.0 exploration architecture study that was released on September 19, 2007 at the AIAA "Space 2007" Conference in Long Beach, CA. According to the group, this paper was created within a 9-month study. The paper provided detail on how the launch vehicles would be one component of a wider-reaching architecture for enabling the US to maintain the ISS, fly lunar missions, and provide additional capabilities for the NASA human spaceflight program. These capabilities included missions to Mars, Lagrangian point staging architecture options, and mission architectures for visiting Near-Earth object destinations..

v2.0 criticism and rebuttal

In June 2008, David King, director of NASA's Marshall Space Flight Center stated that NASA has considered DIRECT as well as many other rocket proposals, and that the Ares family was the right set of rockets for the mission. "DIRECT v2.0 falls significantly short of the lunar lander performance requirement for exploration missions as specifically outlined in Constellation Program ground rules. The concept also overshoots the requirements for early missions to the International Space Station in the coming decade. These shortcomings would necessitate rushed development of a more expensive launch system with too little capability in the long run, and would actually increase the gap between space shuttle retirement and development of a new vehicle. Even more importantly, the Ares approach offers a much greater margin of crew safety - paramount to every mission NASA puts into space."

In July 2008, following NASA statements of no special studies on DIRECT, the space agency released some internal studies conducted in 2006 and 2007. Nearly a year later, on May 18, 2009, the DIRECT team released a rebuttal to the charges raised by NASA, concluding: "NASA’s October 2007 analysis of DIRECT, on the surface, appears to be a carefully executed analysis of the DIRECT architecture and its central launch vehicle, Jupiter. However, a closer examination of the document reveals significant flaws in the evaluation of DIRECT that set up a scenario where DIRECT would inevitably look inferior when compared to Ares. The errors are so numerous that the only conclusion possible is that this document cannot be used to properly assess the value of the DIRECT alternative."

DIRECT v3.0

On 29 May 2009, DIRECT spokesperson Stephen Metschan gave a presentation to the 28th Annual International Space Development Conference in Orlando, Florida entitled, "Direct 3.0: Landing Twice the Mass on the Moon at Half the Cost." In April 2009, following NASA trade studies comparing use of the Space Shuttle Main Engine (SSME) to the originally planned RS-68 engine for Ares V, the DIRECT Team announced that future DIRECT proposals would recommend SSME as the core-stage engine. The engine change was due to concerns that the ablatively-cooled RS-68 would not survive the intense heat produced by the nearby exhaust plumes of the Space Shuttle SRBs. DIRECT asserts that the higher cost of the regeneratively-cooled SSME will be offset by the time and money saved by not human-rating the RS-68. Similarly, for the upper stage, the DIRECT Team recommends using six of the flight-proven RL-10B-2 engines.

On 17 June 2009, team member Stephen Metschan presented the DIRECT v3.0 concept to the Review of United States Human Space Flight Plans Committee chaired by Norman R. Augustine. The competing concepts presented included NASA's current baseline scenario in development (Ares I and Ares V), commercial alternatives such as the United Launch Alliance Delta IV and SpaceX Falcon 9, and a side-mounted Shuttle-Derived Heavy Lift Launch Vehicle concept presented by Space Shuttle Program Manager John Shannon based on the previously proposed Shuttle-C.

Design considerations

Expanded diagram of the DIRECT v2.0 Jupiter-120 configuration

DIRECT v2.0 performance examples

The DIRECT Team asserts that DIRECT v3.0 performance should be similar to the following DIRECT v2.0 examples: According to its proponents, initial DIRECT v2.0 performance to Low Earth Orbit (LEO) [specifically to 42x120nm, 28.5-degree inclination initial orbit] for this initial variant of the DIRECT Crew LV was expected to be 46,635 kg (102,812lb). This meant that an Orion spacecraft could be launched on top of the vehicle, along with 24,600 kg (54,000lb) of additional cargo on every flight. NASA's current baseline crew vehicle Ares I does not allow cargo transport alongside crew transport.

Expanded diagram of the DIRECT v2.0 Jupiter-232 configuration

An optional upper stage, known as the Earth Departure Stage (EDS), powered by two Pratt & Whitney/Rocketdyne J-2XD engines would be used to increase payload capacity for certain missions. Payload performance to LEO would have increased to at least 103,342 kg (227,829lb). Two DIRECT v2.0 J-232 vehicles, one launching crew and spacecraft and the other launching mostly propellant, would have been capable of launching in excess of 220,000 kg (485,000lb), including margin reserves. In comparison, NASA on its official website currently states that Ares V will be capable of lifting 188,000 kg (414,000lb) into lower Earth Orbit and Ares I 25,000 kg (55,000lb)

DIRECT v3.0 - existing engine use

One of the primary goals of the DIRECT proposal is to develop a new heavy lift rocket in a short 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 for its upper stage.

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 some replacements for 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 news 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.

Crew safety

DIRECT envisions continued development and operation of NASA's Orion crewed spacecraft, including its launch abort system. In the event of an emergency, the Orion Launch Abort System 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 metric tons, versus 25 metric tons 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

Thrust oscillation are a concern for Ares I flights

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 J-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

Ares V has a low LOM risk factor according to NASA

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.

Controversy and Criticism

Ares I/Ares V cost and schedule vs. DIRECT

Ares I/V Costs

One of the strongest programmatic criticisms with the current Ares I and Ares V architecture is the high cost for both developing two new launchers and for operating two concurrent programs. The cost concerns have been cited in GAO Reports to Congress noting that the Ares I alone is expected to cost up to $14.4 billion to develop. Former NASA Administrator Michael D. Griffin confirmed that the total cost for developing both Ares launchers would be $32 billion, indicating that the Ares V will be more expensive to develop than the Ares I.

Ares I schedule

The schedule for Ares I has incurred several delays since the inception of the new lunar program. The original intent in the Exploration Systems Architecture Study (ESAS) Report was to have a crewed CEV flight as early as mid-2011 after the Space Shuttle would be retired at the end of 2010. The official current NASA schedule has a 65% confidence that the first manned flight of Ares I with Orion (Orion 2) will occur in March 2015.

The critical activity of Ares I development is currently the schedule for the J-2X upper stage engine and the five-segment version of the SRB. Engineers are concerned about thrust oscillation and Orion-Ares I integration. In 2008, Lockheed Martin requested that NASA redesign Ares I in order to end integration risks with the Orion crew capsule.

DIRECT self comparison to Ares

Direct 3.0 uses SSMEs which are human rated

DIRECT contends that the requirement to develop 5-segment SRBs and the J2-x upper stage engine for Ares I in order to fly the first Orion is directly responsible for the delays in schedule the comparatively high development costs. All-new manufacturing at the Michoud Assembly Facility and new launch facilities at Kennedy Space Center are also required for Ares I. In contrast, DIRECT proposes to reuse the existing 4-segment Space Shuttle Solid Rocket Booster and Space Shuttle Main Engine which are already fully qualified for human use and reuse existing manufacturing to build a modified variant of the existing Space Shuttle External Tank. Only moderate modifications would be required at Kennedy Space Center to enable launches. DIRECT’s proposal for a single launch vehicle removes the program risks associated with the possible cancellation of the Ares V launcher due to budgetary constraints.

DIRECT asserts its Jupiter launchers avoid the delays of Ares I by not requiring the J-2X on the first-generation Jupiter-130 vehicle, by not requiring the five-segment SRB and by providing more than 60 t of lift performance that would ameliorate weight issues on the Orion design.

DIRECT also claims that money would be saved by avoiding a parallel development of the Ares V booster, since the Jupiter family would represent a single rocket family program. The group suggests that the money saved on Ares V be reused to speed development work of such other elements as the Orion, the Jupiter-130, launch facility modifications and all associated systems. A significant cash injection is expected to allow the schedules of all those elements to be significantly trimmed allowing full operational capability of an Orion/Jupiter-130 system to perform 6-person crew rotations and cargo deliveries to the ISS by 2013.

Cost savings and Space Shuttle gap

Proponents assert that the DIRECT proposal would enable NASA to fulfill the mandate of the Vision for Space Exploration sooner and more safely than the planned Ares I and Ares V, at a lower cost and with less programmatic risk due to a simpler approach which decreases new development efforts. Advocates say the DIRECT proposal would allow NASA to provide sufficient money to continue funding programs beyond launch vehicle development and operation, including extending its participation in the International Space Station, which is scheduled to end in 2016 as of 2009. In contrast to these claims, NASA senior manager for the STS program, John Shannon has stated that he thinks the DIRECT proposal underestimates the costs for the Jupiter rocket family. The DIRECT proposal also suggests that NASA uses costs savings from the DIRECT proposal to accelerate the VSE's schedule for returning to the Moon and to potentially fly other missions such as servicing missions to the Hubble Space Telescope.

Orbital assembly steps

Currently, the DIRECT proposal requires more orbital assembly steps than the current proposed Constellation Program. In Constellation, after low Earth orbital rendezvous of Ares I and Ares V, the Orion Crew Exploration Vehicle (approximately 22 t) from the Ares I would invert and dock with the Altair lunar lander (approximately 44 t) which would still be attached to the Ares V Earth Departure Stage. In the case of DIRECT, the combined mass of Orion and Altair exceeds the carrying capacity of the J-130. If a J-130 were launched with Orion and a J-246 launched with Altair, the Jupiter Upper Stage (JUS) with Altair would have insufficient propellant to push Altair/Orion beyond Earth orbit. Thus, the current DIRECT baseline is to launch two J-246s, one with a partially fueled (75 t) JUS carrying Orion/Altair and the other with only a fully fueled (175 t) JUS. After orbital rendezvous, the Orion would invert and re-dock with Altair much like in the Apollo Program and Constellation above. Additionally, however, with DIRECT, the crew in Orion would would have to separate Orion/Altair from the first JUS and blindly dock Altair to the second JUS which would have enough remaining propellant to serve as the Earth Departure Stage. The first JUS would be discarded in Low Earth Orbit, while the second would be discarded after its Earth departure burn.

Jupiter Upper Stage mass

The Jupiter Upper Stage (JUS) mass to propellant capacity has been regarded as unrealistic. Minimal upper stage mass is desirable so that the stage may propel the Orion and Altair spacecraft out of Earth orbit, but the JUS must be made large enough to carry enough propellant to both achieve low Earth Orbit and to serve as the Earth departure stage. The DIRECT v3.0 JUS has a mass of 11.3 t for a propellant capacity of 175.5 t. While claiming a design heritage from the Centaur series of upper stages, DIRECT specifically cites new materials, new welding techniques, and a common bulkhead separating the Liquid Oxygen and Liquid Hydrogen tanks as sufficient to account for the low stage mass. Bernard Kutter of United Launch Alliance described the even more radical DIRECT v2.0 JUS design as, "very reasonable. I’d even call it conservative."

Payload capacity

The payload capacity of Ares V to low earth orbit, according to NASA, is 188,000 kg. This is more than the largest proposed Jupiter rocket (J-246 Heavy with 5 segment SRBS) which is claimed to lift about 120,000 kg to LEO . For potential Mars missions the currently envisioned Ares V would have a significant advantage for any mission architecture. Although in the case of a Mars mission it can be argued that the internal payload fairing diameter is the limiting factor, not mass, due to Mars Entry, Descent and Landing limitations. The DIRECT team have studied payload fairings of up to 12m diameter and even beyond for the Jupiter launch vehicles. The Jupiter rockets are also shorter in height than the Ares V, permitting very long payload fairings and thus greater total internal volume than possible with the taller Ares V which quickly encounters restraints due to height limitations within the Vehicle Assembly Building at KSC.

External Links

• DIRECT Launcher proposal website
• TeamVision page about DIRECT
• DIRECT 3.0 presentation
• v2.0.2 Updated PDF Baseline Proposal
• v2.0.1 Updated PDF Baseline Proposal

• November 2006 NASASpaceFlight.com article on DIRECT
• AIAA Space 2007 Conference presentation in High Res or Low Res
• TheSpaceReview.com commentary on ESAS including DIRECT
• TheSpaceReview.com article about DIRECT
• NASAspaceflight.com forum
  • Original 2006 post by Ross Tierney that led to the DIRECT idea
  • DIRECT v1.0 discussion (now locked at 131 pages)
  • DIRECT v2.0 discussion (now locked at 250 pages)
  • DIRECT v2.0 Thread 2 discussion (now locked at 300 pages)
  • DIRECT v2.0 Thread 3 discussion (now locked at 250 pages)
  • DIRECT v2.0 Thread 4 discussion (13 pages)
  • DIRECT v3.0 discussion

• Q&A: ESAS Lead - Dr Doug Stanley (On DIRECT)
• TheSpaceShow.com interview about DIRECT, 07/01/2007 issue
• A DIRECT approach, Horizons, American Institute of Aeronautics and Astronautics - Houston Section, 32,3 (Summer 2007), cover, 5-12.
• TheSpaceShow.com interview about DIRECT, 02/17/2008 issue and related presentation in PDF
• TheSpaceReview.com article about DIRECT by Stephen Metschan, "There is a better way forward" Part One and Part Two
• Orlando Sentinel article about DIRECT : "NASA remains silent on rocket that could rescue the Cape" June 22, 2008 Retrieved on 2009-06-04.
• International Space Development Conference presentation in PPS
• NASA engineers design maverick moon rocket MSNBC, July 14, 2008
• Saving America's Space Program - The Space Review Aug 11, 2008
• Article about Direct on Popular Mechanics
• New Scientist - In search of NASA's next rocket Illustration with DIRECT pros and cons
• Revisiting a DIRECT approach, Horizons, American Institute of Aeronautics and Astronautics - Houston Section, 34,2 (Summer 2009), 8-11.
• Marking 40 Years Since Apollo 11 NPR - Talk of the Nation, July 17, 2009. Includes Ross Tierney of DIRECT.

• 85 Unclassified Technical Documents about the National Launch System (NLS) - the 1991 NASA/USAF Predecessor which DIRECT is based upon