Aeronautics and astronautics – Spacecraft – With fuel system details
Reexamination Certificate
2001-09-28
2002-12-03
Swiatek, Robert P. (Department: 3644)
Aeronautics and astronautics
Spacecraft
With fuel system details
C060S224000
Reexamination Certificate
active
06488237
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the use of propellant feed systems in the aerospace field, and more particularly to a system and method of controlling propellant cross-feed between a booster and an orbiter of a two-stage rocket.
BACKGROUND OF THE INVENTION
Increasing the thrust to weight ratio (T/W) of a rocket (or other type of launch vehicle) can result in a concomitant increase in the payload capability, or performance, of the rocket. In general, the thrust to weight ratio of the rocket may be increased by decreasing the weight of the rocket and/or increasing the thrust of the rocket. Two-stage rockets typically have two-stage propellant burn, a booster stage and a continuing (orbiter) stage. The booster stage is generally provided by a booster that includes booster engines that are connected to a booster tank using a booster feed line. Similarly, the orbiter stage is typically provided by an orbiter that includes orbiter engines that are connected to an orbiter tank using an orbiter feed line. Each engine is fed propellant for combustion from its respective tank and through its prospective feed line. During launch, the booster bums during the first, booster stage until a disconnect sequence is initiated. Then, the orbiter ignites and separates from the booster to begin the continuing stage, burning until the orbiter reaches orbit.
For the typical two-stage rocket, much of the thrust of the booster is devoted to supporting the weight of the vehicle. As the early trajectory of the rocket is nearly vertical to the Earth's surface, the weight of the vehicle results in significant gravity losses. Increasing the T/W well above 1.0 minimizes the effect of such gravity losses until the rocket is in a flight path more nearly horizontal to the Earth's surface. Once in a more horizontal trajectory, the thrust of the orbiter may be more effectively used to increase velocity rather than fight gravity. Additional booster engines, or larger booster engines, could increase the amount of thrust available but are generally undesirable due to the cost and additional weight of the engines.
A cross-feed system used with the two-stage rocket can significantly increase payload capacity by “borrowing” the orbiter engine to increase the T/W during the boost phase using propellant supplied from the booster. Conventional propellant cross-feed systems include a cross-feed line connecting the booster and orbiter feed lines. The cross-feed system allows both the booster and orbiter engines to burn simultaneously during the booster stage so as to increase thrust. The additional thrust allows the orbiter to overcome gravity losses that are incurred during the early flight period. The borrowed orbiter engine is transferred back to the orbiter near the end of the boost phase. The still-firing orbiter engine propels the orbiter back into orbit using propellant from the orbiter tanks. Advantageously, the propellant cross-feed system promotes a more efficient overall use of propellant as the more efficient orbiter engines burn for the longest time. A more efficient use of propellant reduces the amount of propellant that must be carried by the rocket, thereby reducing the weight of the rocket.
Some cross-feed systems include several motorized valves that facilitate the transition from cross-feed to continuing stage operation. In one prior art system, the cross-feed system includes a cross-feed line having a motorized closing valve and an open-latched, swing pivot valve. Also, the orbiter feed line includes a second motorized valve for controlling propellant supply to the continuing engine. The latched open swing pivot valve is on the orbiter side and when unlatched will close off to seal the cross-feed line for separation. The two motorized valves of the cross-feed system allow the engines to consume propellant from only the booster tanks during the first part of the ascent mission. However, the motorized valves must be stringently timed and sequenced to avoid significant propellant flow back to the booster and to avoid starving the orbiter engine(s) during the transition phase. Such timing or sequencing requirements may pose reliability problems. In addition, the more complex, moving parts a system has, the greater the chance of reliability problems. Reliability is a highly sought-after feature in aerospace applications.
Therefore, it would be advantageous to have a propellant cross-feed system that increases the performance of a rocket by increasing the thrust-to-weight ratio. It would be further advantageous to have a propellant cross-feed system with fewer moving or complex parts and therefore a higher reliability. It would also be advantageous, if the propellant cross-feed system minimized timing and sequencing problems.
SUMMARY OF THE INVENTION
The present invention addresses the above needs and achieves other advantages by providing a propellant cross-feed system and method for supplying a propellant which is burned by a booster and orbiter engines of a rocket. The cross-feed system includes a cross-feed line connecting a booster supply line for supplying propellant to the booster engine and an orbiter supply line for supplying propellant to the orbiter engine. The cross-feed line allows propellant to flow from the booster supply line to the orbiter supply line. Propellant flow to the orbiter supply line allows the orbiter engines to burn in parallel with the booster stage engines. Backflow of propellant from the orbiter to the booster is limited by a low pressure drop check valve that closes when pressure in the orbiter line is higher than the booster line. The flow of propellant in the orbiter line is controlled by a motorized switch-over valve that opens slowly during the process of switching over from the booster stage to the continuing stage. As the flow in the orbiter line is increased, the pressure at the orbiter end of the cross-feed line also increases, causing the low pressure drop check valve to progressively close. Advantageously then, the low pressure drop check valve responds to control of the switch-over valve, obviating the need for complex valve control and sequencing schemes.
In one embodiment, the present invention includes a two-stage rocket having a booster and an orbiter, the two-stage rocket also having a propellant cross-feed system capable of supplying propellant simultaneously to both the booster and the orbiter. The rocket includes a booster and orbiter propellant tanks each capable of containing a reservoir of propellant. The booster and orbiter engines are each capable of burning the propellant and producing thrust. The rocket further includes a booster supply line connecting in fluid communication the booster propellant tank to the booster engine. The booster supply line supplies the propellant at a flow rate to the booster engine. An orbiter supply line connects in fluid communication the orbiter propellant tank to the orbiter engine. The orbiter supply line supplies the propellant at a flow rate to the orbiter engine. The rocket also includes a cross-feed system. The cross-feed system includes a switch-over valve connected to the orbiter supply line. The switch-over valve controls the flow rate of the propellant in the orbiter supply line. The cross-feed system also includes a cross-feed line connecting the booster supply line and the orbiter supply line in fluid communication. The cross-feed line has a first pressure at its booster end and a second pressure at its orbiter end. The cross-feed line includes a low pressure drop check valve configured to begin closing as the second pressure exceeds the first pressure. An increase in the flow rate of the propellant in the orbiter supply line by the switch-over valve results in an increase of the second pressure so as to begin closing the low pressure drop valve. Closing of the low pressure drop check valve inhibits the flow of the propellant from the orbiter supply line to the booster supply line.
In another embodiment, the low pressure drop check valve is a swing check valve. The swing chec
Glasser Sidney P.
Sosa Charles J.
Swiatek Robert P.
The Boeing Company
LandOfFree
Propellant cross-feed system and method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Propellant cross-feed system and method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Propellant cross-feed system and method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2976034