Cryogenics in the Space Industry

Dennis A. Lobmeyer and Dr. Barry Meneghelli

     The current state of the art in space launch systems uses cryogenic chemical propulsion, that are primarily liquid hydrogen and liquid oxygen, to provide the energy necessary to achieve orbit and escape the bounds of Earth’s gravity.  As we move away from earth there are additional options for propulsion. Unfortunately, few of these options can compare to the speed or ease of use provided by the cryogenic chemical propulsion agents currently in use.

     Cryogenics, the science and art of producing cold operating conditions for use on earth, in orbit, or on some other non-terrestrial body, has become increasingly important to our ability to travel within our solar system. The production and transport of cryogenic fuels as well as the long-term storage of these fluids is necessary for mankind to travel within our solar system.  It is with great care and at a significant cost that gaseous compounds such as hydrogen and oxygen are liquefied and become dense enough to use for rocket fuel. 

     As our explorations move further away from the boundaries of earth we need to address how it is that we will be able to produce the necessary fuels in order to make a complete round trip back to our home planet.  The cost and the size of any expedition to another celestial body are both extreme at best.  If we constrain ourselves with the need to take everything, fuel, life support, etc. necessary for our survival while away as well as those quantities necessary to effect our return we invalidate any chance of travel in the not too distant future.  As with the early explorers on earth, we will need to harvest much of our energy and our life support from the celestial bodies that we visit.  The “In-situ” production of these energy sources is paramount to our success.  Once again due to the design of our propulsion systems today, these “In-situ” processes will also require liquefaction and the application of cryogenics. 

     The challenge that we face for the near future is to increase our understanding of cryogenic long term storage and off-world production of cryogenic fluids.  We must do this all within the boundaries of very restricted size, weight and robustness parameters so that we may launch these apparatus from earth and utilize them elsewhere. Miniaturization, efficiency, and physically robust systems will all play a part in making space exploration possible, however it is cryogenics that will enable all of this to occurThe current state of the art in space launch systems uses cryogenic chemical propulsion, that are primarily liquid hydrogen and liquid oxygen, to provide the energy necessary to achieve orbit and escape the bounds of Earth’s gravity.  As we move away from earth there are additional options for propulsion. Unfortunately, few of these options can compare to the speed or ease of use provided by the cryogenic chemical propulsion agents currently in use.

Chemical Engineering in Space

Dennis A. Lobmeyer and Dr. Barry Meneghelli

     The aerospace industry has long been perceived as the domain of both physicists and mechanical engineers.  This perception has endured even though the primary method of providing the thrust necessary to launch a rocket into space is chemical in nature.  The chemical engineering and chemistry personnel behind the systems that provide access to space have labored in the shadows of the physicists and mechanical engineers.  As exploration into the cosmos moves farther away from Earth, there is a very distinct need for new chemical processes to help provide the means for advanced space exploration.  The state of the art in launch systems uses chemical propulsion systems, primarily liquid hydrogen and liquid oxygen, to provide the energy necessary to achieve orbit.  As we move away from Earth, there are additional options for propulsion. Unfortunately, few of these options can compare to the speed or ease of use provided by the chemical propulsion agents.

     It is with great care and significant cost that gaseous compounds such as hydrogen and oxygen are liquefied and become dense enough to use for rocket fuel.  These low-temperature liquids fall within a specialty area known as cryogenics. Cryogenics, the science and art of producing cold operating conditions for use on Earth, in orbit, or on some other nonterrestrial body, has become increasingly important to our ability to travel within our solar system.  The production of cryogenic fuels and the long-term storage of these fluids are necessary for travel.

     As our explorations move farther away from Earth, we need to address how to produce the necessary fuels to make a round-trip.  The cost and the size of these expeditions are extreme at best.  If we take everything necessary for our survival for the round-trip, we invalidate any chance of travel in the near future.  As with the early explorers on Earth, we need to harvest much of our energy and our life support from the celestial bodies.  The in situ production of these energy sources is paramount to success.  We are currently working on several processes to produce the propellants that would allow us to visit and explore the surface of Mars.

     The capabilities currently at our disposal for launching and delivering equipment to another planet or satellite dictate that the size and scale of any hardware must be extremely small.  The miniaturization of the processes needed to prepare the in situ propellants and life support commodities is a real challenge. Chemical engineers are faced with the prospect of reproducing an entire production facility in miniature so the complex can be lifted into space and delivered to our destination. 

     Another area that does not normally concern chemical engineers is the extreme physical aspects payloads are subjected to with the launch of a spacecraft.  Extreme accelerations followed by the sudden loss of nearly all gravitational forces are well outside normal equipment design conditions.  If the equipment cannot survive the overall trip, then it obviously will not be able to yield the needed products upon arrival.  These launch constraints must be taken into account.

     Finally, we must consider both the effectiveness and efficiencies of the processes.  A facility located on the Moon or Mars will not have an unlimited supply of power or other ancillary utilities.  For a Mars expedition, the available electric power is severely limited.  The design of both the processes and the equipment must be considered.  With these constraints in mind, only the most efficient designs will be viable.

     Cryogenics, in situ resource utilization, miniaturization, launchability, and power/process efficiencies are only a few of the areas that chemical engineers provide support and expertise for the exploration of space.

Insulation Testing Using Cryostat Apparatus With Sleeve

James E. Fesmire and Stan D. Augustynowicz

          The method and equipment for testing continuously rolled insulation materials is presented in this paper.  Testing of blanket and molded products is also facilitated.  Materials are installed around a cylindrical copper sleeve using a wrapping machine.  The sleeve is slid onto the vertical cold mass of the cryostat.  The gap between the cold mass and the sleeve measures less than l mm.  The cryostat apparatus is a liquid nitrogen boiloff calorimeter system that enables direct measurement of the apparent thermal conductivity (k-value) of the insulation system at any vacuum level between 5x10-5 and 760 torr.  Sensors are placed between layers of the insulation to provide complete temperature-thickness profiles.  The temperatures of the cold mass [maintained at 77.8 kelvin (K)], the sleeve [cold boundary temperature (CBT)], the insulation outer surface [warm boundary temperature (WBT)], and the vacuum can (maintained at 313 K by a thermal shroud) are measured.  Plots of CBT, WBT, and layer temperature profiles as functions of vacuum level show the transitions between the three dominant heat transfer modes.  For this cryostat apparatus, the measurable heat gain is from 0.2 to 20 watts.  The steady-state measurement of k-value is made when all temperatures and the boiloff rate are stable.

Cryogenic Insulation System for Soft Vacuum

Stan D. Augustynowicz and James E. Fesmire

     The  development of a cryogenic insulation system for operation under soft vacuum is presented in this paper.  Conventional insulation materials for cryogenic  applications can be divided into three levels of thermal performance, in terms  of apparent thermal conductivity [k-value in milliwatt per meter-kelvin (mW/m-K)].  System k-values below 0.1 can be achieved for multi-layer insulation operating at a vacuum level below 1x10-4 torr.  For fiberglass or powder operating below 1x10-3 torr, k-values of about 2 are obtained.  For foam and  other materials at ambient pressure, k-values around 30 are typical. New  industry and aerospace applications require a versatile, robust, low-cost thermal insulation with performance in the intermediate range.  The target for the new composite insulation system is a k-value below 4.8 mW/m-K (R-30) at a  soft vacuum level (from 1 to 10 torr) and boundary temperatures of approximately 77 and 293 kelvin (K).  Many combinations of radiation shields, spacers, and  composite materials were tested from high vacuum to ambient pressure using  cryostat boiloff methods.  Significant improvement over conventional systems in  the soft vacuum range was demonstrated.  The new layered composite insulation  system was also shown to provide key benefits for high vacuum applications as well.

Cryogenic Insulation Systems

S. D. Augustynowicz, J.E. Fesmire and J.P. Wikstrom

     The results of a comparative study of cryogenic insulation systems performed are presented. The key aspects of thermal insulation relative to cryogenic system design, testing, manufacturing, and maintenance are discussed.  An overview of insulation development from an energy conservation perspective is given. Conventional insulation materials of cryogenic applications provide three  levels of thermal conductivity. Actual thermal performance of standard  multilayer insulation (MLI) is several times less than laboratory performance and often 10 times worse than ideal performance.  The cost-effectiveness of the  insulation system depends on thermal performance; flexibility and durability;  ease of use in handling, installation, and maintenance; and overall cost  including operations, maintenance and life cycle.  Results of comprehensive  testing of both conventional and novel materials such as aerogel composites using cryostat boil-off methods are given.  The development of efficient, robust cryogenic insulation systems that operate at a soft vacuum level is the primary  focus of this paper.

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