Ultra Long Duration Balloon Technologies
Recent advances in composite superpressure balloon materials have greatly enhanced the prospects for very long duration balloon flights on Earth as well as possible use for planetary exploration. The strawman vehicle would support a ~1 ton scientific payload on a 16-28 mcf (million cubic feet) superpressure balloon for 100 days (~5 circumnavigations of the globe). This configuration could maintain stable altitude from day to night without ballast. The Ultra Long Duration Balloon Vehicle will fly at both high and low latitude bands and can experience 12 hour periods of night or continuous daylight. Significant power, 1- 2 kW, is required to power scientific detectors and support systems. The power system must be capable of functioning continuously for the duration of the mission at varying power levels. Many of the scientific instruments require cryogenic temperatures to cool the detectors. Thermal control must be maintained in daytime and nighttime conditions. Some of the experiments call for daily data return, daily commanding or even hourly commanding. NASA is seeking innovative and cost effective solutions in support of this development activity. Below are candidate technology areas but others may be proposed. NASA is currently defining requirements and identifying technologies and technical resources that are requisite for the development of this new capability.
Balloon Vehicle and Recovery System Technologies
The Ultra Long Duration Balloon Vehicle, with volumes up to 1 million cubic meters must survive an extreme set of environmental conditions beginning with the fabrication of the material and balloon through launch, ascent and float. NASA is seeking innovative and cost effective solutions in support of this development activity in the following areas:
High strength to weight composite envelope materials suitable for fabrication into balloon vehicles;
Efficient and cost effective seaming methods and technology suitable for joining of composite materials for the fabrication into balloon vehicle;
Real time balloon seam quality inspection methods and technology;
Buoyancy control methods to limit balloon diurnal excursions or temperature/differential pressure fluctuations;
Low cost, reliable water recovery systems for balloon payloads;
GPS guided parafoil system suitable for global autonomous operation for recovery of ballooncraft;
Latitude trajectory control for altering balloon trajectories on a global basis to avoid overflight of no-fly zones.
Balloon Borne Power System
The Ultra Long Duration Balloon Vehicle can fly at both high and low latitude bands and can experience 12 hour periods of night or continuous daylight. Significant power, 1- 2 kW, is required to power scientific detectors and support systems. The power system must be capable of functioning continuously for the duration of the mission at varying power levels. NASA is seeking innovative and cost effective solutions in support of this development activity. Below are candidate technology areas but others may be proposed.
Solar
The system must be designed, weight and size, for the worst case operating conditions for each the polar flights and the low latitude flights. The size of the system is not as much a concern as the size of the stowed system for launch. Deployable arrays, which can be either unrolled or inflated, may be a very desirable option. A sterling engine may also be an approach for using solar energy.
New battery technology
We want deep discharge but only 100 cycles + some margin. A fuel cell system can be attractive for high power "short" flights (1 kW, 20 days) or for moderate power for longer flights (200 W, 100 days). Fuel cells also offer the advantages of "waste heat" for thermal control, water drops for ballasting, and the possibility of using the waste water for thermal storage (solar heated during the day and acting as a supplemental heat at night). Flywheel energy storage systems Wind power generators suspended a few hundred or thousand feet below the balloon craft.
Cryogenic Mechanical Refrigerators
Many of the scientific instruments require cryogenic temperatures to cool the detectors. NASA is seeking innovative and cost effective solutions in support of this development activity. We require very low cost mechanical refrigerator systems capable of cooling more than one Watt of input load to ~90K. We are also interested in systems capable of cooling small thermal loads to 4K. We expect to be receiving proposals from the UNEX program with a total cost of $5M for the entire program, so cost must be very low. The mission duration for the ultra long balloon project will be 100 days, so we can accept substantially shorter lifetimes than traditional satellite programs. The payloads will normally be recovered and reflight is quite inexpensive, so we can afford accept lower standards of reliability if they produce substantial reductions in cost. The scientific payload weight is ~1 ton, so weight is not as critical a parameter as cost. Power during the 12 hours of darkness on a balloon will be at a premium, so we want systems that can be stopped and started on each of the 100 days.
High Efficiency Heat Pump System
NASA is seeking a high efficiency active thermal control system for a long duration balloon experiments. Total thermal loads will be in the 300 to 2000 W range. Altitude of operation will be 100 to 130 K-ft (residual pressure between 11 and 3 millibars). The output thermal load must be radiated to the Earth or to space under all possible conditions (clouds, over water, over land, ice etc.) We require thermal control on the input side to +/- 10 degrees C with a goal of +/- 1 degree C. Thermal control must be maintained in daytime and nighttime conditions (12 hours daylight and 12 hours darkness at low latitudes). Expected mission lifetime is ~100 days and we require a mean time to failure >200 days.
Communications and Data Storage
Options for the return of high rate science data are limited. Some of the missions require real time response. Some of the experiments call for daily data return, daily commanding or even hourly commanding. TDRSS and Military satellites cannot be relied on to give balloons top priority, therefore other options need to be explored. NASA is seeking innovative and cost effective solutions in support of this development activity. Areas of interest include but are not limited to:
A very low cost, compact, rugged mass data storage system with >1 terabit capacity. We are seeking a reusable system in the <$100K range. Several of these systems may be used for on-board recording. Data will be recovered by high speed data dumps or possibly by parachuting to the ground (must withstand 10 g shocks). The system needs to be able to operate at altitudes between 100000 and 130000 feet (pressures between 11 and 3 millibar). It needs to operate from a 28 V unregulated battery input. The operating temperature range without thermal control may be extreme so an extended operating temperature range is desirable.
Increased telecommunication rates and coverage by use of various communications satellite options such as TDRSS, Commercial (Little LEO, LEO, MEO, Geosync.), military (USA, Russian), amateur radio operator satellites or use of new antenna Technologies.
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