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*Transportation and Carriers
*ISS Support
*Space Shuttle
*Progress spacecraft,russian expendable freighter unmanned resupply spacecraft
*Automated Transfer Vehicle , expendable unmanned resupply spacecraft developed by the European Space AgencyThe United States space exploration goals expressed in January 2004 call for the retirement of the Space Transportation System (STS or Shuttle) following completion of International Space Station (ISS) construction. Since the Shuttle is instrumental in transporting large quantities of cargo to and from the ISS, this functional capability must be preserved to ensure ongoing station operations in a post-Shuttle era. Fulfilling ongoing cargo transport requirements to the ISS is a prime opportunity for NASA to reduce costs and preserve and repurpose the unique and limited Shuttle resource by acquiring cargo transportation services commercially. Further, implementing such a service prior to retirement of the Shuttle reduces risk to the vehicle and her crews by eliminating their use for routine cargo transport missions while accelerating the readiness for alternative ISS-support transportation.In January of 2004, President Bush directed NASA to begin an initiative that focuses on exploration of the Moon, Mars, and beyond. This initiative calls for the completion of International Space Station (ISS) assembly by the end of the decade coincident with retirement of the Space Shuttle [G.W. Bush, A Renewed Spirit of Discovery: The Presidents Vision for U.S. Space Exploration, January 2004.] . Retirement of the Shuttle while ISS operations are still being conducted results in reduced capability to supply ISS logistics requirements. An examination of existing and planned logistics carriers shows that there are deficiencies in both capacity and capability to support ISS needs. SPACEHAB's history of space station logistics delivery and existing ground infrastructure coupled with NASA's mandate and documented intent to acquire commercial space systems and services when possible has led SPACEHAB to develop a versatile and affordable cargo transport service for ISS . [United States Congress, National Aeronautics and Space Act of 1958, as amended, Public Law 85-568, 1984.]
tate of ISS logistics capability
ISS cargo requirements
As of 2004, the United States Space Shuttle, the Russian Progress, and to a very limited extent, the Russian Soyuz vehicles are the only systems capable of transporting ISS cargo. Before the end of ISS assembly, it is anticipated that the European Automated Transfer Vehicle (ATV) and Japanese H-IIA Transfer Vehicle (HTV) will be introduced into service. The US Shuttle transports the majority of the pressurized and unpressurized cargo and provides virtually all of the recoverable down mass capability.
Cargo vehicle capabilities
An understanding of the future ISS cargo requirements is necessary to size a commercial cargo vehicle designed to replace the Shuttle's capabilities and capacities and augment currently planned alternative vehicles. Accurate estimates of ISS cargo transfer requirements are difficult to establish due to ongoing changes in logistics requirements, crew tending levels, vehicle availabilities, and the evolving role the ISS will play in NASA's space exploration and research goals.An increased unpressurized cargo delivery requirement is shown during the years 2007–2010. This increased rate is a result of a current plan to preposition unpressurized spares on the ISS prior to Shuttle retirement. Provision of a commercial cargo carrier capable of transporting unpressurized spares to supplement the Shuttle eliminates the prepositioning requirement and aligns the estimated averages during 2007–2010 to approximately 24,000 kg for pressurized cargo and 6800 kg for unpressurized cargo. Considering the delivery capability of the remaining systems after the Shuttle is retired yields.Retirement of the Shuttle and reliance on the Progress, ATV, and HTV for ISS logistics will result in no significant recoverable down-mass capability. Further, no evidence suggests that any of these cargo transport systems can increase production and launch rates to cover the cargo delivery deficiency.
Commercial opportunity
In addition to ISS support deficiencies, alternative opportunities for a commercial cargo transport system exist. The retirement of the Shuttle will also result in an inability to conduct Low Earth Orbit (LEO) research independent of the ISS. A commercial payload service could serve as a free-flying research platform to fulfill this need.As logistics support requirements for NASA's space exploration initiative emerge, existing commercial system can be employed.
Finally, nascent interest in the development of non-government commercial space stations must take resupply issues into consideration. Such considerations will undoubtedly be subjected to a make/buy analysis. Existing systems which have amortized their development costs across multiple government and non-government programs should favor a “buy” decision by commercial space station operators. As these markets arise, commercial companies will be in a position to provide logistics services at a fraction of the cost of government-developed systems. The resulting economies of scale will benefit both markets. This conclusion was reached by a Price-Waterhouse study chartered by NASA in 1991 [ Price Waterhouse, Analysis of NASA lease and purchase alternatives for the commercial Middeck augmentation module, 1991.] . The study concluded that the value of SPACEHAB's flight-asset-based commercial module service with an estimated net-present-value of $160 million would have cost the US government over $1 billion to develop and operate using standard cost plus contracting. SPACEHAB's commercial operations and developments (such as the Integrated Cargo Carrier) since 1991 represent further cost savings over government-owned and operated systems.
Commercial companies are more likely to efficiently invest private capital in service enhancements, assured continued availability, and enhanced service capability. This tendency, commonplace in non-aerospace applications, has been demonstrated by SPACEHAB in the commercial space systems market via continued module enhancements and introduction of new logistics carriers.
Shortfalls in ISS cargo transport capacity, emerging opportunities, and experience gained from SPACEHAB's existing ground and flight operations have encouraged development of our Commercial Payload Service (CPS). As a commercially developed system, SPACEHAB recognizes that to optimize its capability and affordability requires that certain approaches in system development and operations be taken.
The first approach levies moderate requirements on the system. Introducing fundamental capabilities on the front end and scarring for enhanced capabilities later reduces cost to launch and shortens development time.
The second one is the utilization of existing technology and capabilities, where appropriate. A typical feature of NASA programs is the continual reach for newly developed technologies. While attractive from a technical advancement perspective, this quest is expensive and often fails to create operational capabilities. A commercially developed cargo module will maximize the use of existing technologies (off the shelf where possible) and seek technical advances only where system requirements or market conditions drive the need for such advances. Additionally, costs associated with the development of spacecraft are not limited to those associated with the vehicle systems. Significant costs associated with the infrastructure must also be considered. SPACEHAB's existing logistics and vehicle processing facilities co-located with the Eastern launch range and at the Sea Launch facilities enable avoidance of significant system development costs.
Finally, SPACEHAB has realized cost and schedule reductions by employing commercial processes instead of Government processes. As a result, SPACEHAB's mission integration template for a Shuttle-based carrier is 14 months, compared to 22 months for a similar Shuttle-based Multi-Purpose Logistics Module (MPLM) [National Aeronautics and Space Administration, Station program implementation plan, vol. 6: Cargo Physical Integration, SSP 50200-06, December 1997.] .
Rack transfer capability
The ISS utilizes the International Standard Payload Rack (ISPR) as the primary payload and experiment accommodations structure in all US operated modules. Transferring ISPRs onto and off the ISS requires passage through the View the MathML source in hatch only found at the Common Berthing Mechanism (CBM) berthing locations. The diameter of the CBM combined with ISPR proportions typically drives cargo vehicle diameters to sizes only accommodated by 5 m payload fairings launched on Evolved Expendable Launch Vehicles (EELV).
Recoverable reentry–pressurized payloads
The Russian Progress vehicle has long served as a cargo vehicle which, upon departing a space station, destructively reenters the atmosphere destroying all “cargo” on board. This approach works very effectively for removing unwanted mass from a space station. However, NASA has indicated that the return of payloads from the ISS is highly desirable [5] . Therefore, a commercial system must examine the implications of including a pressurized payload return capability either in the initial design or as an enhanced feature of the service to be introduced in the future. Providing such capability requires the incorporation of thermal protection subsystem, deorbit targeting subsystems, landing recovery subsystems, ground recovery infrastructure, and FAA licensure. The recovery of unpressurized payloads presents unique challenges associated with the exposed nature of unpressurized carriers. To implement a recoverable reentry system for unpressurized payloads requires the development of an encapsulation system. Encapsulation activities must either occur autonomously prior to reentry or as a part of the operations associated with loading the unpressurized cargo carrier with return cargo. In either case, additional cost associated with spacecraft systems or increased operational requirements will be higher than simply loading and departing a pressurized carrier for a destructive reentry.
Mixed manifest capability
Typically, the avoidance of point solutions provides flexibility for a given system to provide variable capabilities. Designing a cargo carrier that mixes pressurized and unpressurized systems can lead to increased cost if all associated cargo accommodations must be flown on every flight. To avoid unnecessary costs associated with designing and flying structure that accommodates fixed relative capacities of all types of payloads, a modular approach is taken for CPS. Anticipated cargo transport requirements for ISS after the Shuttle is retired indicate that dedicated pressurized and unpressurized missions can support the ISS up-mass requirements. Utilizing common base features (i.e. service module, docking system, etc.) and modularizing the pressurized and unpressurized carrier elements of the spacecraft assures flexibility while avoiding point solutions.
Propellant transfer
The Russian Segment of the ISS (RSOS) has the capability via the probe and cone docking mechanisms to support propellant transfer. Incorporation of propellant transfer capability introduces international issues requiring the coordination of multiple corporate and governmental organizations. Since ISS propellant requirements are adequately provided for by the Russian Progress and ESA ATV, costs associated with incorporating these features can be avoided. However, the CPS’ modular nature coupled with the inherent capability of selected subsystems enables economical alternatives to propellant transfer should ISS needs require.
Indirect costs considered in developing the CPS architecture include licensing requirements associated with International Traffic in Arms Regulations (ITAR) and the Federal Aviation Administration (FAA) commercial launch and entry licensing requirements. ITAR licensing drives careful selection of the vehicle subsystem suppliers. Any utilization or manufacturing of spacecraft subsystems by non-US entities can only be implemented once the appropriate Department of State and/or Commerce approvals are in place. FAA licensing requirements necessitate careful selection of the launch and landing sites. Vehicles developed by a US organized corporation, even if launched in another country, require review of the vehicle system, operations, and safety program by the FAA to ensure that risks to people and property are within acceptable limits [Federal Aviation Administration-Office of Commercial Space Transportation, 14 CFR, November 2000 (Chapter III).]
References
Acta Astronautica
Volume 57, Issues 2-8, July-October 2005, Pages 257-265Infinite Possibilities Global Realities, Selected Proceedings of the 55th International Astronautical Federation Congress, Vancouver, Canada, 4-8 October 2004
[ [http://findarticles.com/p/articles/mi_qa3766/is_200501/ai_n15869342 Space Logistics: The Ultimate Logistics Enterprise Challenge | Logistics Spectrum |] ]
ee also
* [http://spacelogistics.mit.edu/] MIT project about Space Logistics
*CSTS Crew Space Transportation System
