Aeronautics and astronautics – Spacecraft – Attitude control
Reexamination Certificate
2001-03-28
2004-02-03
Jordan, Charles T. (Department: 3641)
Aeronautics and astronautics
Spacecraft
Attitude control
C244S158700, C244S164000
Reexamination Certificate
active
06685141
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to the field of launch vehicles. More particularly the invention relates to launch vehicular configurations including X33 aeroshell, external tank, and bell nozzle rocket engines.
BACKGROUND OF THE INVENTION
The recently conducted, space transportation architecture study reviewed a wide range of launch concepts all proposed as options to replace the space shuttle. An independent assessment of these concepts determined that none were able to satisfy the wide range of design requirements that are demanded of a system to replace the space shuttle. The majority of the proposed launch systems are also being designed to meet commercial space lift needs. This commercial market demands that an additional set of challenging requirements be met.
One of the most demanding of the system design requirements for a launch system that is capable of performing both Civil (NASA) and commercial missions is to limit the development cost for the complete system to, on the order of, $2 Billion dollars. Using present year dollars, this figure is less than 10% of the original development cost of the space shuttle system. A number of contributing factors limit the development cost that is allowable. There is a the high cost on return on investment to obtain development funds for high risk development. There is a long duration between initial investment and an operational system with associated revenues. There is a the relatively small addressable launch market once operations begin. And, there is the relatively unknown demand elasticity environment in the launch market.
In addition to requiring low development costs, any system that is to replace the space shuttle must also be extremely reliable. This reliability is required not only over the long haul but also from the onset of initial operations. In addition, the new system must meet new manned flight human rating safety standards established by NASA. One of these safety standards demands that the system provide the ability for safe crew escape capability throughout the entire flight trajectory. The new set of safety standards is considerably more stressing than those required of the current space shuttle system. In fact, no other transportation system requires full crew escape throughout the entire journey. Rather, current transportation systems, such as commercial aircraft, are designed to be inherently safe and reliable and also provide for graceful degradation rather than accept catastrophic failure modes in the design.
Independent of NASA safety needs, the numerous direct and indirect costs associated with a catastrophic failure event implies the need for an extremely reliable design that precludes, within practicality, catastrophic system failures. Examples of design features that help to prevent such catastrophic failures include: full engine out from liftoff, full vehicle abort capability throughout the entire mission, robust design and operating margins, and integrated vehicle health management. The integrated vehicle health management working in conjunction with the vehicle management system provides the capability to anticipate impending system failures and or react promptly to unanticipated failures and take appropriate action to mitigate the risk associated with such failure. Such a capability implies heritage of the major system components and subsystems so that nominal and off nominal operating conditions can be recognized and dealt with accordingly. The alternative to a large degree of design heritage is to conduct an extremely expensive flight test program in which the system is fully characterized before revenue generating flight begins. This later option is most likely prohibitive in the space launch industry due to the small launch market in which to amortize these costs. The integrated vehicle health management system also provides vehicle health information in order to enable rapid and low maintenance cost turnaround of the launch system in preparation for the next mission. This capability is needed to meet cost goals. A requirement to allow incremental flight test is also important and allows the launch system to be characterized prior to subjecting it to overly stressing conditions. This incremental approach allows operating changes or design fixes to be incorporated before design or fabrication problems are allowed to cause a serious failure.
Other performance related requirements relating to space lift capability and recurring cost must also be met. The space shuttle orbiter has an injected weight of approximately 170K pounds with the exact weight being orbiter specific, for an enclosed usable volume for propellants and payload of 11K cubic feet. Using a metric of the ratio of injected mass to enclosed volume, the shuttles orbiter metric is 15.5, and is unsuitable for housing both propellant and a sizable payload. The system must lift approximately 25K pounds of cargo and crew to the international space station orbit and also be able to return crew and cargo from the international space station safely to Earth. It is also highly desirable that the launch system be able to evolve to support future Mars exploration missions. This demands a much heavier lift capability to low earth orbit than required for the international space station alone. Furthermore, to justify even a modest investment in a new launch system, the recurring cost must be low on the order of providing commercial space lift prices of less than $2,500 per pound including fully amortized development and production costs as well as cost of financing and allowance for profit.
The ideal concept should also be capable of evolving into a third generation launch system. Such a system would be capable of providing extremely low launch costs, in the range of $100 to $500 per pound, with levels of operability and reliability comparable to those of aircraft. This set of almost mutually exclusive design requirements for low development and operation costs, extreme reliability and safety, heavy lift, evolutionary capability, and heritage with flight proven hardware could not be met by any of the launch systems recently proposed to replace the Shuttle. Consequently, the transportation architecture study concluded that because no near term launch system could satisfy all of these requirements, the U.S. should continue operation of the space shuttle well into the future.
The space shuttle orbiter employs a wing body configuration and was designed with structural and thermal protection materials available since the late 1970s. The consequence of orbiter design approach and then available technologies yielded a vehicle design with a poor figure of performance in terms of the ratio of internal volume compared to the overall dry mass of the vehicle. The internal volume is used principally to house either propellants or payload. The poor internal volume to mass ratio of the space shuttle orbiter dictated the need for a large quantity of propellant and thus liftoff mass to accelerate the space shuttle orbiter and the payload to orbital velocity. Ultimately, the poor liftoff performance led to a decision that a rocket booster stage would be required to provide both the majority of liftoff thrust and initial acceleration, or impulse, of the space shuttle system. Segmented solid rocket motor powered boosters were selected for this purpose. The solid rocket boosters were intended to provide lower development costs than would reusable liquid boosters. However, the solid rocket booster operations significantly increased both operating costs and catastrophic failure modes of the space shuttle system. The extensive solid rocket booster recovery and refurbishment activities required after each flight also contributed to the large operations cost increase associated with the solid rocket boosters.
The solid rocket booster also had other liabilities. Once lit, the solid rocket boosters could not be turned off until their solid propellants were fully consumed. This is a major contributor to the inability of the space shuttle orbiter and the crew t
Jordan Charles T.
Reid Derrick Michael
Semunegus Lulit
The Aerospace Corporation
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