Engineering topics

Snow, W. R.

Publications and source records attributed to Snow, W. R..

7 records

NASA NTRS1982

Mass Driver Two - A status report

The current status of Mass Driver Two, a linear synchronous motor for accelerating payloads or reaction mass, is discussed. Mass Driver Two combines all the essential elements of an operational mass driver with the exception of bucket recirculation and payload handling. These essential elements include: magnetic flight, vacuum environment, superconducting bucket coils, high acceleration (nominally 500 g's), optical position sensing and electronic triggering, power circuitry similar to that of a flight article, and regenerative braking. Mass Driver Two is operated on a single shot basis.

Snow, W. R.↗

NASA NTRS1982

Mass driver reaction engine characteristics and performance in earth orbital transfer missions

Configurations of a typical mass driver reaction engine (MDRE) are presented and its use for delivery of payloads to geosynchronous orbit (GEO) from low earth orbit (LEO) is discussed. Basic rocket equations are developed for LEO to GEO round-trip missions using a single exhaust velocity. It is shown that exhaust velocities in the 5-10 km/sec range (specific impulse of 500-1000 sec) are well suited for mass drivers, minimizing the overall cost of missions. Payload delivery rate fractions show that there is little to be gained by stretching out LEO to GEO transfer times from 90 to 180 days. It therefore pays to use the shorter trip time, approximately doubling the amount of delivered payload during any fixed time of use of the MDRE.

Snow, W. R.↗

NASA NTRS1981

A small scale lunar launcher for early lunar material utilization

A system for the launching of lunar derived oxygen or raw materials into low lunar orbit or to L2 for transfer to low earth orbit is presented. The system described is a greatly simplified version of the conventional and sophisticated approach suggested by O'Neill using mass drivers with recirculating buckets. An electromagnetic accelerator is located on the lunar surface which launches 125 kg 'smart' containers of liquid oxygen or raw materials into a transfer orbit. Upon reaching apolune a kick motor is fired to circularize the orbit at 100 km altitude or L2. These containers are collected and their payloads transferred to a tanker OTV. The empty containers then have their kick motors refurbished and then are returned to the launcher site on the lunar surface for reuse. Initial launch capability is designed for about 500T of liquid oxygen delivered to low earth orbit per year with upgrading to higher levels, delivery of lunar soil for shielding, or raw materials for processing given the demand.

Snow, W. R.↗

NASA NTRS1981

The supply of lunar oxygen to low earth orbit

Since oxygen makes up 86% of the total mass of propellants which would normally have been brought up from the earth to LEO, considerable savings are available if this oxygen can be obtained from the moon for little Delta-V penalty. This paper presents a scenario in which 400 T/yr of LOX is delivered to LEO, with the ability for upgrading to 5000 T/yr. In this scenario, cylindrical tanks of liquid oxygen with a mass of 500 kg are launched from the lunar surface by a mass driver and rendezvous with a collection station in a 100-km lunar orbit. The oxygen is removed from each tank and placed into a tanker OTV which later will transfer from low lunar orbit to LEO with an aerobraking maneuver. Launch requirements for aerobraked chemical OTVs using earth oxygen are compared to those using lunar oxygen.

Andrews, D. G.↗

NASA NTRS1979

Construction and testing of the 2.5m mass driver

Presented are the designs used in the construction of the 2.5 m mass driver and the results of the initial testing program. The mass driver consists of equal length sections of acceleration and deceleration each containing 59 drive coils of 13.1 cm caliber. Intermediate energy storage is provided by sector capacitors which are recharged every half cycle by an external power source. The drive coils are individually energized through SCR's with timing supplied by position sensing optical detectors. The drive consists of two phases which operate in quadrature. The initial bucket to be propelled through the mass driver contains two coils of aluminum wire chilled to liquid nitrogen temperatures to momentarily sustain superconducting field intensities. Magnetic flight is generated by eddy current repulsion from six copper guide strips lining the mass driver. Nominal acceleration is 5000 m/sec per sec giving a maximum bucket velocity of 112 m/s.

Snow, W. R.↗

NASA NTRS1979

Overview and outline of Mass-Driver Two

An overview of the Princeton-M.I.T. second mass-driver is presented. Mass-Driver Two is a 13.1 cm caliber system which uses a two coil superconducting bucket and a two-phase in quadrature drive system. Discrete drive coils are individually energized with timing supplied by position-sensing optical detectors. Intermediate energy storage is provided by sector capacitors which are recharged every half cycle by an external power source. A vacuum environment is provided for the superconducting bucket by a 4 inch ID glass pipe with the drive coils surrounding it. Magnetic flight is generated by eddy current repulsion from six copper guide strips lining the glass pipe. The length is 2.5 meters equally divided between acceleration and deceleration sections. Nominal acceleration is 5000 m/sec per sec giving a maximum bucket velocity of 112 m/sec. Regenerative braking is used to decelerate the bucket. Current densities of 25 sq cm are achieved in the superconducting bucket coils and are maintained by a cryogenic service station.

Oneill, G. K.↗

NASA NTRS1973

A Module for Automatic Dock and Detumble (MADD) for orbital rescue operations

The module for automatic dock and detumble (MADD) is an automated device for bringing a passive, tumbling space base under control in an orbital rescue situation. The conceptual design of such a device resulted from a consideration of tumbling motion analyses and mission constraints. Specific topics of investigation include orbit and attitude dynamics and detumble profiles. Position and attitude control systems for the various phases of operation were developed. Dynamic motion of a passive vehicle with MADD attached is considered as an example application and to determine control requirements. Since time is a critical factor in rescue operations, it is essential to execute the detumbling maneuver in a minimum of time. Optimization of the MADD thrusting sequence has also been investigated. Results indicate the control torque must be directed opposite to the angular momentum vector for the assumption used here.

Snow, W. R.↗