In Memoriam T. Brian Gray|
SPACE WORK STATION
Combining Capacity and Capability at Low Cost
(Extracts from a transcription of a 2-hour video presentation produced in 1991*)
In February of 1969 it was Nationally reported that NASA was planning for a "100-Man Station" and that the "Cost of such a station over a period of years has been estimated at in excess of $10 billion."(1) I assumed a cost of $30 billion for the 1969 100-man station and plotted the cost per astronaut for '69, '84 (8-man station for $8 billion), and 1992 (4-man station for $32 billion). The results are shown by the solid line in Figure 1. [Figure currently unavailable]
Why has the cost grown so great for this much smaller station? Has our space technological capability decreased in the last 22 years? No, its a result of less launch capability and more politics.
In 1969 we had the Saturn V booster, which could launch massive, completely furnished space station modules into orbit. Because we now have much less launch capability, the space station' modules, and every component within them, must be made as compact and as lightweight as is technically possible, and that is expensive.
Because there is not enough room within the modules for some of the equipment and experiments, they must be mounted externally, and therefore be designed to withstand the hostile elements of the space environment, and that is expensive.
Because there is no cost effective way of repairing or adjusting the external elements, and very little room to repair the internal elements, they must be made to be failure free. To make the elements that perfect, each of their components must be ultra-reliable or the complete systems must have extensive redundancy, and both of these options are very expensive.
I have found a way to design a Shuttle derived cargo vehicle that is affordable, because it is (more correctly - its components are) reusable. Thus large, completely furnished space station modules can be launched, which saves launch and assembly costs and reduces the expensive size and mass minimization requirements now imposed on each and every component of the current design.
The Space Work Station's Design Rules are as follow:
We should use existing Space Shuttle hardware for the critical launch phase:
The Space Work Station has over ten times the internal volume of the US portion of the old (read: original Freedom Space Station) design, which was larger than the new (read: current International Space Station) design. Each of these large modules, essentially identical to the hydrogen tank portion of the current Shuttle system external tank, has over 53,000 cubic feet of internal volume. Each spoke of the rotating section includes two of the shuttle external tanks. Shuttle external tanks are extremely strong and lightweight and are produced on an assembly line as affordably as possible, since one is discarded each time the shuttle flies. The external tanks provide still more pressurized volume for storage in orbit. Each external tank adds over 73,000 cubic feet of storage space.
It can be assembled in phases. Phase I consists of one man-tended module and the truss. Artificial gravity is utilized in Phase II to simplify and lower the cost of fluid management within the rotating section. Phase II illustrates only one of many possible configurations made possible by utilizing these massive pressurized modules. There is no required EVA, and Phase II is completed after only four launches of the low cost shuttle derived Modular Cargo Vehicle (MCV).
Phase III would allow for additional growth: the length of the spokes can be increased easily since the cargo modules can be linearly bolted to each other in series until the desired length is reached. If no further spoke length is required, a phase IV expansion could build the rim of the wheel to become the familiar wheel space station like that proposed by Wehrner von Braun in the 50's, and that shown in the movie: "2001, Space Odyssey."
Modular Cargo Vehicle (MCV)
Consider instead a similar vehicle designed to be launched only to transportation nodes in space, the first node being the space station of course. There the expensive Shuttle propulsion and avionics components can be removed, and brought back to Earth in returning Shuttle Orbiters. Figure 2 shows a possible configuration for that low cost heavy lift vehicle built from already tested and proven shuttle components. I call it a Modular Cargo Vehicle. [Figure currently unavailable]
The propulsion system is identical to the Shuttle Orbiter, although those components dealing only with reentry and landing have been deleted. The nose module consists of the Shuttle forward reaction control system and the forward section of the cabin, which contains avionics bays one and two. As you can see a large fuel tank and one orbital maneuvering system (OMS) engine have been added to the basic structure and a panel has been added to close out and seal the avionics bay section. The complete nose module is released from the cargo vehicle at the space station and fits directly into the cargo bay of a shuttle orbiter which is ready to return to Earth.
The cargo module is derived from Shuttle external tank components and can be put to use as a large pressurized space station module in orbit. Each of these space station modules provides 53,470 cubic feet of pressurized volume. This is approximately 12 times the maximum internal volume of NASA's new downsized 27 foot long space station modules. The expensive weight and size reduction process required for the smaller modules can thus be avoided.
The MCV has extremely low development costs since over 98% of its components have been repeatedly space qualified with each Shuttle launch. Operational costs are 1/3 ($/lb.) those of the Shuttle
Orbital Pressurizable Hangar (OPH)
The engine module is obviously too large to fit into the Orbiter cargo bay, but contains components which are too expensive to discard. They are recovered utilizing a large pressurizable hangar, which is part of the first cargo module launched to the space station. The hangar is over 40 feet deep, and over 25 feet in diameter, the rest of the module is pressurized for habitation. As you can see the entire engine module fits within the hangar and the components can be removed by remotely controlled manipulators or by astronauts working within the pressurized shirt-sleeve environment of the hangar.
There are two hangars in the work station. One is here in the non-rotating module. . . The other is up here in the hub module. These hangars provide a cost-effective method of adjusting, repairing, and maintaining any orbiting element which can fit within its 25 foot inner diameter hatch. Thus external space station elements no longer have to be ultra reliable -- they can be cost effectively repaired without risky EVA (Extra Vehicular Activity -- that is an astronaut space walk). This greatly lowers the cost of the external space station components.
The Space Work Station's Beam Assembler produces beans that are composed of rigid preformed triangles joined by semirigid rails and flexible tension crosswires. Even though the side rails are not completely rigid, and can be rolled onto reels when separate from the triangles, the resulting completed beam is quite rigid, prevented from deforming by the crosswires. The pins that hold the rails to the triangle apexes are removable to allow the beam to be disassembled. Freed from the side rails, the triangles stack compactly against each other in a small fraction of the space occupied by the completed beam.
One advantage of the semi-rigid rails is that the beam can be curved by modifying the lengths of the cross wires as shown in figure 3 [Figure currently unavailable]. No modification of the beam assembler is required. Additional structure must be added next to the curved sections to compensate for this localized flexibility.
Unlike NASA's Beam Builder, the Beam Assembler automatically forms beams of unlimited length and shape which are used to form the Space Work Station truss. The final configuration formed by the Beam Assembler is a continuous loop around the Space Work Station, that forms a continuous railroad along which the mobile manipulators could travel.
Almost all of the authorities assume that slow rotation artificial gravity would eliminate most if not all of the detrimental effects of micro-gravity and would be more desirable than mandatory heavy exercise for several hours a day or than experimenting with drugs, but it is assumed that such a system cannot be affordable at this time. Also, since it has never been demonstrated, it is doubtful that Congress would back such a very expensive unproven cure. Yet demonstrating artificial gravity to the public and Congress would settle what I consider the biggest question regarding the future of our space program.
Most of the experts agree that less than two rpm will probably be tolerable to all the astronauts. The assumption that has stopped a practical solution to the long term effects of space travel and habitation is that we need artificial gravity at an equivalent level to Earth's as a starting point. We should direct our efforts at first developing artificial gravity at the lunar level.
It turns out that, with the large cargo modules used as space station modules, simulated lunar gravity at only 1.6 rpm is technically easy to achieve. Cargo modules can be modified to include an extension cylinder which, when extended, increases the distance of the cargo module from the rotating hub (195 feet) to create lunar level artificial gravity with a rotation speed of only 1.6 rpm. This produces the complete range of artificial gravity from zero along the rotation axis to simulated lunar gravity at the far end. Under these conditions we will learn of the long term effects of lunar gravity, necessary to intelligently design a lunar base.
Under artificial gravity fluids behave similarly to the way they do on Earth, greatly simplifying such normal habitation needs as sinks, toilets, showers and kitchen facilities, and avoiding the high costs of unique zero-g systems.
Plants can be grown in artificial gravity for air and water purification, and to provide fresh vegetables. Artificial gravity at the lunar level will decrease if not eliminate the negative physiological effects of micro-gravity on astronauts.
The attitude stabilization produced by the gyroscopic effect of the rotation greatly reduces the requirement for attitude control propellants.
Major Advantages of the Space Work Station
3- Heavy-Lift Vehicle and means for future space construction:
4- Artificial gravity:
If our advance into space depended only on technology, we would be much farther along by now. Unfortunately politics is involved, and nothing happens in politics without a strong pushing force. The impressive size and capabilities of the Space Work Station should favorably impress the public and Congress, providing more support for future projects, and will return the undisputed leadership in space and technology to the United States, and it is about time we did that.
* Video presentation produced by Jeannette Jaquish. Screenshot used by permission.