VII  LAUNCH, SEPARATION, AND TRANSFER FUNCTIONS

 

 

          A. The Launching Function

 

          The launching process is the principal means by which control of the system is effected.  In this, the launch function makes the definitive decision: whether or not to launch.  With few exceptions, once launched, the carrier proceeds inexorably to its destination. 

 

          The process begins with the carrier stationary on a launching track, and has signaled the requisite information, including destination, and its readiness to be launched.  The launch system will have received data about the next available packet(s) from the upstream station via the sector monitor.  These data will include the location of the packet, the number of carriers, along with the destination of each.  Upstream sensors, adjacent to the main track, will have confirmed this.  These data links are essential, If for any reason these should fail, no launches are permitted.     

 

          The launch computer compares these data with the quota requirements of the extant scenario, and makes a determination of whether a launch is permitted.  These may include a single launch, or in some instances it may be desirable to launch multiple carriers

 

          These decisions will depend mainly on anticipated requirements down stream, and the need for equality of access to the system.  During periods of light traffic, the system may allow the launching of a new single-carrier packet; again this would depend on anticipated system demand. It may also be desirable to designate certain whole packets as transfer packets to another line.

 

          There is no guarantee that randomly entering individual vehicles will present themselves in the precise order required by the system, thus busy stations may require more than a single launch track. 

 

          In all respects the maintenance of precise, periodic packet oper­ation is an overarching con­sideration.  With appropriate consideration for all of the above, the launch system determines the next available launch. 

 

          Having determined that a valid launch window does exist, the launch system signals the launch carrier.  The carrier is instructed to begin a specific acceleration protocol designed to bring it parallel (actually slightly behind) and matching the speed of the appropriate packet.  The packet should be traveling at the system speed, but the onboard sensors will confirm that, this, and all other conditions for a launch, are extant - no launch will take place if all are not within prescribed limits.  Satisfied, the launch carrier, still guided by the transfer arm, transfers to the main line, re-engages the main guide, and attaches itself to the end of the packet.

 

          In the unlikely event that the predicted launch window is, in fact, not available, the launch carrier will not engage its transfer arm and comes to an immediate stop.  The carrier signals the launch system, and the procedure is re-initialized and begun again.

 

 

          B.  The Separation Function

 

          The function of the separation system is to provide a smooth transition from the main line to the exit station.  As described in Section IV, a carrier wishing to depart signals the packet, established an exit distance, engages the transfer rail, and departs the main line.

 

          As we are dealing with close-packed carriers, a single separation line can accommodate only a fraction of the main line traffic.  This fraction is essentially the ratio of the speed in the exit station to that of the main line; some­thing of the order of ten percent.  On average, this may be entirely adequate for a particular station.  If not, multiple parallel lines may have to be considered.  The operative phrase, however, is on average.  Since we have placed no restrictions on the order within a packet, an orderly system must accom­modate instan­taneous rates two or three time this, possibly higher. 

 

          If it is to operate properly, the system can not allow any slow down on the main line.  Accordingly, no carrier may begin braking until well clear of it.  To accommodate this requirement, a buffer track is provided.  If there are no previous carriers in the separation system, an exiting carrier will travel to the end of the buffer before executing the braking protocol.  Subsequent carriers would then be instructed to commence their own braking at an appropriate distance upstream from the end of the buffer.  It should be noted, however, that these instructions are intended for a routine, uneventful halt.  The onboard sensors on each carrier continually monitor the situation ahead, and should the occasion warrant, call an emergency stop.

 

          As with the launch system, the separation system would be provided all pertinent data from the sector monitor.  However, we emphasize that these data are not essential to the safe operation of the system.  The system only need record the departure time of the last carrier and sense an arrival of the next to calculate the appropriate braking point.  Thus a failure in communication would not jeopardize exiting the system.

 

 

          C.  Transfer Between Lines

         

          A transfer from one line to another is essentially a combination of exiting and re-launching.  That is, upon approaching a selected transfer point, the carrier signals the packet its desire to exit in the usual manner.  It exits and under the direction of the transfer system it slows to a transfer speed.  By timing the beginning and duration of the transfer speed, the transfer system effectively synchronizes the two lines.  The relationship of carriers leaving a particular packet and the packet designated to receive them is fixed, and of pre-determined order.  In this way the specific packet assignment of any carrier can always be determined, assuming only that it has not been denied a transfer.  If such a denial has taken place, a specific record is maintained.

 

          This transfer speed will, in general, by about one-half of the system speed.  This provides two advantages.  One, on the occasion of multiple transfers from within a single packet, it allows the transfer carriers to form-up into a single mini-packet and append to the receiving packet as a unit.  The second advantage is that significantly shorter guideway radii can be accommodated without discomfort to the passengers.  It should be noted, however, that by limiting the transfer speed, the capacity of the transfer guide is limited correspondingly, i.e., to essentially half the capacity of the main line.  This should not prove problematical since if a majority of the anticipated traffic would wish to transfer, that direction is simply designated the continuation of the main line. 

         

          After the carrier(s) have exited the main line, all movement within the transfer area is under the direct control and supervision of the transfer function.  It is this agency that must determine the initial time and duration of the transfer speed to insure that carrier(s) arrive at the new line in a timely manner.  As with the separation system, the onboard sensors on each carrier will detect any abnormal operation, and initiate appropriate action if necessary.

  

          Obviously, the receiving line must provide an empty slot.  While this is an essential part of the coordinating scheme of allocating quotas and priorities provided by the overall system, the transfer function also plays a vital, if redundant, role.  Trackside monitors must confirm that an empty slot does in fact exist.  If no actual vacancy exists, the carrier is brought to a complete stop.  It will then subsequently be launched within existing quotas for the new (or transfer) station.  Accordingly, as with the separation system, it is essential that transfer functions have sufficient buffer space to receive any exiting carriers and/or packets, and if necessary bring them to a complete stop.  

 

          As we indicated in Section IV, if there is an actual vacancy in the designated packet, a carrier will be allowed to switch even if it exceeds the specific quota for this transfer.  It will be classified as a potential conflict and appropriate sector monitors on the receiving line will be notified.  This, so that, if need be, appropriate action can be taken.

 

          Alternatively, it may be desirable to switch whole packets from one line to another.  This would be primarily at locations where very heavy interchange traffic is expected.  This would not be available at all locations inasmuch as special express transfer lines capable of operation at full system speed must be available.  Since whole packet transfer does not involve slowing to the transfer speed, the relation between packet location on the old line and on the new line will be different.  Thus close coordination to provide an empty packet slot is a requirement.

 

          Under this procedure, the packet leader instructs all the carriers in the packet to grasp the transfer rail in the same manner as an individual exit.  It should be noted that each carrier would be an­ticipating this command as each knows how to get where it wants to go.  If for one reason or another, a particular carrier failed in this endeavor, it would simply proceed on the original line as a single-carrier packet.  This would cause an inconvenience to the commuter, but no serious problem for the system.