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Dual Launch Vehicle

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Overview of the Space Island Group's (SIG's)
Dual-ET Launch Vehicle Model


Our first goal at the Space Island Group (SIG), when it was incorporated in California in late 1999, was to use non-government funds to finance the design, construction, launch and operation of very large commercial space stations built from a re-engineered version of the space shuttle's orange, hollow external fuel tank, or ET. Our second goal was to design, build, launch and operate transport vehicles to move large numbers of people up to these stations and back down to Earth.

Dozens of studies done by NASA and aerospace companies over the last (20) years have verified that building space stations from NASA's current ETs is feasible, but expensive. The studies pointed out that with a few critical ET design changes, assembling and operating these stations could be done far more efficiently. SIG is aggressively pursuing those changes with our aerospace corporate partners.

Our second goal was to build transport vehicles able to safely and economically carry thousands of people to the stations every year, and eventually every month.

Our initial plan was to redesign the space shuttles to create a safer, less expensive, passenger-carrying version. Most of this website describes this combination of ET-stations served by commercial space shuttles. After all, NASA's shuttle prototypes have flown over (100) flights during the last (20) years. They work, but like all prototypes, they're expensive and dangerous to operate. SIG understands that both those conditions can be changed by engineering improvements.

We calculated that re-designing the ETs and building our first unmanned 'Dual-ET' vehicle would cost about $2 billion and take 3-4 years. It would have one fuel-filled ET with engines at its lower end, and space shuttle solid rocket boosters attached to its sides. Mounted on the side of this first ET, between the (2) boosters would be a second, empty ET that could carry cargo to orbit, or its interior could be outfitted in advance as living and working quarters for at least a dozen people.

This outfitted version could have hatchways built between the (2) ETs before launch. Once in orbit the crew, carried up later on a manned vehicle, could move into the prefabricated ET and activate its systems. Within a few days, after the excess fuel was removed from the first ET, they could enter it through the hatchways and outfit its interior for other commercial uses.

As more Dual-ETs are launched they will be attached to the sides of the first one in orbit. A year after the first launch this cluster of ETs will form a huge, zero-g manufacturing and satellite repair facility with living quarters for nearly (200) people.

At that point some of those crew members will begin assembling other newly arrived ETs into the wheel-shaped, rotating space stations seen on this website. Today this part of SIG's original plan is being developed with our aerospace partners. But the passenger-carrying space shuttles are another matter.

Developing these new shuttles will take (5) years, and cost $5-$6 billion. It's still on SIG's agenda, but in the fall of 2003 a simpler alternative emerged. The alternative is to combine the Dual-ET launcher with the DC-X, or Delta Clipper, a prototype of which was built in the early 1990s.

The following illustrations and text explains that the Clipper could be ready for orbital tests in 3-4 years, at a cost of $2-$3 billion. It could carry 20-30 people up and back. That's less than a 75-passenger space shuttle, but it could profitable serve the needs of SIG's ET-stations for the next decade. It's also scaleable, so during the next decade SIG would have the option of building the new shuttles, or building larger versions of this manned vehicle.

Final design of the Dual-ET/Delta Clipper combination will be completed in late 2004 or early 2005, and the first launch could take place in late 2007. It all goes well the second launch would occur (3) months later, and another would follow every month thereafter. Below are definitions of the main Dual-ET elements.

External Fuel Tank

This is a re-engineered version of the space shuttle's orange, hollow external fuel tank, or ET.

Its overall dimensions will be the same (approximately 27.5 feet by 154 feet) to utilize current factory tooling, but it an extra 20-25 foot segment will be added to its lower end to house (3) liquid hydrogen/liquid oxygen engines. Those engines will be improved versions of the ones mounted in the tail of NASA's Space Shuttle's. Structural elements at the ET's lower end and elsewhere will be redesigned to handle these new loads, and wall thickness in other area may be increased to improve radiation or micro-meteor protection on orbit.

These changes may increase the ET's overall weight substantially over its current 66,000 pounds, but the new engines will compensate for that increase. The ET will be filled with liquid hydrogen and liquid oxygen fuel before launch, as is done with the current shuttle. Re-engineering costs could be as high as $500 million.

Liquid Fuel Engines

The full range of liquid hydrogen/liquid oxygen engines now in production or in late stage development are being considered. The Rocketdyne RS-68, currently in use on the Delta IV unmanned launcher, is one option. The Cobra engine under development by Pratt and Whitney and Aerojet is another. Man rating the RS-68 may cost $200-$300 million or more, and completing development of the Cobra, which is designed as a man-rated engine, may cost the same. The Space Island Group (SIG) is exploring options with several engine developers.

Solid Rocket Boosters

These engines (2 per launch vehicle) will be the same 4-segment versions used on the current Space Shuttle, or an improved, 5-segment version, which is in its final testing stage.

SIG may fund development of reusable, liquid fly back boosters to replace these solid boosters. This could lower launch costs and increase safety margins, but could cost up to $2 billion dollars to develop. SIG is exploring fly backs with several engine developers. In either case the boosters will separate from the primary vehicle about (2) minutes after launch, as the current shuttle boosters do.

Zero Gravity Production/Research Facility

This is essentially the hydrogen section of a standard ET, measuring roughly 27.5 feet by 100 feet. Its interior will be outfitted before launch with living and working quarters for a crew of at least 12. Its standard wall thickness may be increased for additional radiation and micro-meteor protection, and it will contain research, manufacturing production, analytical and product packaging areas.

The SpaceHab Corporation has completed a preliminary study of this interior outfitted as a pharmaceutical production area. It can be seen here.

The section will weight 100,000 pounds, and its development/construction cost will approach $1 billion.

Two passageway/hatches will be built between the habitable section and the fuel-filled ET. Once in orbit the remaining odorless fuel will be removed, and a crew will enter through the hatches to outfit the interior as living quarters and working areas for a variety of commercial markets.

A Soyuz or space shuttle docking port may be built at the bottom of this habitable section on the first (2) launches to allow access until SIG's crew transfer vehicle (see below) is man-rated.

Crew Transport Vehicle

This is a variation of the DC-X (or 'Delta Clipper') single-stage-to-orbit (SSTO) design developed by Dr. Bill Gaubatz and his team at McDonnell Douglas in the early 1990s. The original concept was to place enough liquid oxygen/liquid hydrogen fuel inside the vehicle to let it reach orbit without external fuel tanks or rocket boosters, or perhaps with just a single, small booster rocket. When its orbital task was completed it was to re-enter the atmosphere nose-first, rotate to a tail-first position a few thousand feet above the landing site, then land gently as the retro-rockets in its tail fired. Its design and operating costs were to be a small fraction of the space shuttles. A prototype was built and this landing concept and cost structure was successfully proven, but in the mid-90's the program's federal funding ran out.

A drawback of the concept, common to all SSTO concepts, was that only 1-2% of its interior space was left for cargo or personnel. But combining this Clipper concept with Dual-ET launch eliminates this drawback.

A Clipper-like vehicle attached above the habitable production section would ride to orbit on the thrust of the fuel-filled ET and the boosters. Only 25% of its interior would be needed for engines and landing fuel.

SIG will design at least (3) variations of this vehicle. A manned version will carry 3 dozen people to orbit and back, a second, unmanned version will carry zero-g materials from the factory modules back to Earth, and a third version will remain in orbit permanently to bring damaged satellites to one of SIG's orbiting repair, refueling and upgrade facilities, then return them to their proper orbit.

Each variation will weigh approximately 75,000 pounds. The (3) variations together will cost some $3 billion to develop and test.

The design is scaleable. Longer version could be mounted on the side of the fuel-filled ET, replacing the habitable hydrogen section and eliminating SIG's original, far more expensive plan to build an improved, passenger-carrying version of NASA's Space Shuttle prototypes.

Launch Complexes

Specialized launch complexes for these vehicles will be built in Florida and California at a cost of $200 to $300 million each.

Development & Launch Timelines

SIG expects its first habitable Dual-ET/Clipper vehicle to be launched by late-2007 or 2008. Follow-up launches will occur every (2) months for a year, then every month for another year, then every (2) weeks. Weekly flights could be available early in the next decade, probably with larger versions of the Clipper.

Dual-ET 'clusters' will serve as zero-g industrial centers in 2008. In 2009 the first partial-gravity test facility will be built, consisting of (8) Dual-ETs joined into a cross rotating slowly, like a four blade propeller with braces connecting its tips. Gravity levels at the propeller's hub will be near zero, and will increase as occupants move toward its tips.

Partial Gravity Wheel Stations (1/3 Earth's Gravity)

The first of the 500 person, rotating, wheel stations will be built from 12 or more ETs should be under construction in 2010 or 2011. Once completed, another will be built each following year.

The launch vehicle described above is a 'first draft' concept. Other options are being studied by our aerospace corporate partners, including the possibility of mounting the habitable hydrogen section and the Clipper-like vehicle above the fueled ET, instead of beside it as shown in the illustration, or the main engines may be mounted at the bottom of the habitable hydrogen section. All of the elements above will appear in our final launch vehicles, but those elements may be arranged differently for safety or cost considerations.

    Letter from ATK Alliant Techsystems (PDF)

    Letter from Lockheed Martin (Word Doc)

    Letter from Pratt & Whitney (Word Doc)

    Letter from Space Available, LLC (Word Doc)

    Letter from Vandenberg (Word Doc)

Also see Station & Transport Lease Rates.

Also see Our NASA Moon/Mars Cost Cuts.

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