A document presents a concept for relatively inexpensive delivery of propellant to a large fuel depot in low orbit around the Earth, for use in rockets destined for higher orbits, the Moon, and for remote planets. The propellant is expected to be at least 85 percent of the mass needed in low Earth orbit to support the NASA Exploration Vision. The concept calls for the use of many small (≈10 ton) spin-stabilized, multistage, solid-fuel rockets to each deliver ≈250 kg of propellant. Each rocket would be winched up to a balloon tethered above most of the atmospheric mass (optimal altitude 26 ±2 km). There, the rocket would be aimed slightly above the horizon, spun, dropped, and fired at a time chosen so that the rocket would arrive in orbit near the depot. Small thrusters on the payload (powered, for example, by boil-off gasses from cryogenic propellants that make up the payload) would precess the spinning rocket, using data from a low-cost inertial sensor to correct for small aerodynamic and solid rocket nozzle misalignment torques on the spinning rocket; would manage the angle of attack and the final orbit insertion burn; and would be fired on command from the depot in response to observations of the trajectory of the payload so as to make small corrections to bring the payload into a rendezvous orbit and despin it for capture by the depot. The system is low-cost because the small rockets can be mass-produced using the same techniques as those to produce automobiles and low-cost munitions, and one or more can be launched from a U.S. territory on the equator (Baker or Jarvis Islands in the mid-Pacific) to the fuel depot on each orbit (every 90 minutes, e.g., any multiple of 6,000 per year).
This work was done by Brian Wilcox of Caltech for NASA's Jet Propulsion Laboratory. For further information, access the Technical Support Package (TSP) free on-line at www.techbriefs.com/tsp under the Mechanics category. NPO-42007
This Brief includes a Technical Support Package (TSP).
Low-Cost Propellant Launch From a Tethered Balloon
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Overview
The document outlines a novel approach to launching propellant into Low Earth Orbit (LEO) using a tethered balloon system, developed by the Jet Propulsion Laboratory (JPL) under NASA's Commercial Technology Program. The primary motivation for this innovation stems from the high costs associated with launching propellant, which is essential for missions to the Moon, Mars, and beyond. Currently, launching propellant to LEO costs approximately $10,000 per kilogram, making it financially unfeasible to support ambitious exploration goals that require thousands of tons of propellant annually.
The proposed solution involves using mass-produced, small solid rockets (10-20 tons) launched from a high-altitude tethered balloon at altitudes of 20-24 kilometers. This method allows the rockets to be spun up and launched at a low elevation angle, significantly reducing atmospheric drag and enabling them to reach orbit more efficiently. By employing this technique, the effective launch cost could drop to around $650 per kilogram, making large-scale propellant launches much more affordable.
The document also highlights the potential launch sites, specifically Baker and Jarvis Islands, which are located near the equator. This location is advantageous due to the absence of jet streams and hurricanes, facilitating the tethering of high-altitude balloons. The concept combines historical ideas from the 1950s regarding balloon launches and unguided, spin-stabilized rockets, enhancing them with a simple guidance system that improves orbit insertion accuracy.
The technology is still at the conceptual stage, with no prototypes developed yet. However, it has been presented at conferences, and there are plans for future disclosures to the public. The market for this technology is estimated to be several billion dollars annually, primarily targeting the U.S. government as the main customer.
In summary, this innovative approach to propellant launch aims to drastically reduce costs and support NASA's Exploration Vision by making it feasible to launch the necessary amounts of propellant for deep space missions. The document emphasizes the potential impact of this technology on future space exploration and its alignment with current NASA objectives.
