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Path: utzoo!kcarroll
From: kcarroll@utzoo.UUCP (Kieran A. Carroll)
Newsgroups: net.space
Subject: Re: Oberth Wheels
Message-ID: <3735@utzoo.UUCP>
Date: Mon, 9-Apr-84 14:26:16 EST
Article-I.D.: utzoo.3735
Posted: Mon Apr  9 14:26:16 1984
Date-Received: Mon, 9-Apr-84 14:26:16 EST
References: <304@charm.UUCP>
Organization: U of Toronto Zoology
Lines: 23

*

   The devices which you refer to as "Oberth Wheels" are in fact being
employed on satellites right now, going under the name of "momentum
wheels" or "reaction wheels". They are used in much the way that
you describe, as angular-momentum sinks to allow for the maneouvering
of the satellite about its three axes without the need for reaction
jets. They are also used to "soak up" the angular momentum generated
by the various torques found on orbiting satellites: gravity-gradient,
solar, atmospheric, magnetic, what-have-you. The cyclic components
of these torques are absorbed temporarily by the wheels, and are later
vancelled when the torque reverses direction. The secular component
(or DC, as opposed to AC) is absorbed until the wheel is spinning
at its rated maximum speed, at which time the momentum is dumped
by simultaneously despinning the wheel, and firing the satellites
attitude-control thrusters to provide a balancing torque. Neat, huh?
   The problem with these wheels ( as with all hardware) is that they
possess mass; thus, they may not be used on some satellites, if it
is determined that a set of thrusters with fuel supply for the
length of the mission would weigh less than the wheel system

-Kieran A. Carroll
...decvax!utzoo!kcarroll