Entry Ramp:

 

Entry ramp tubes connect the station to the main tube and must accelerate pods to the system speed (35 MPH) and merge them into the main line traffic without incident. As presently proposed, four pods can enter the ramp at a time, the lead pod launches while three pods load on a moving walk. Reference: Entry Ramp.

 

The portal entry is sealed by a sally-port iris-shaped gate system with an inlet vent located between the sally-port gates. The outer gate opens and the pod enters and the pod wind skirt deploys. The outer gate then closes and the inner gate opens. The inlet vent opens as the main tube fan at the end of the portal ramps up speed. As the pod accelerates past the inner gate, a second set of inlet vents opens, the inner gate closes, and the sally-port vent closes. The outer gate opens and another pod enters. The first pod continues to accelerate up the tube where it hits the junction fly-over and lands on the main tube floor rails.

 

It would take about 10 seconds between launches, with about 7.5 seconds to accelerate the pod to 35 MPH. It would probably be possible to allow serial launches in the same ramp, if higher launch rates are needed, but a longer moving walkway would also be needed on the debarkation platform to increase the number of pods being loaded.

 

The fan cowling on the intake side is extended into the merge area where the cross-section is twice the size of a single tube. The ramp air is extracted here to maintain constant air speed in the main tube. The fan unit is sized for the extra air needed to accelerate the pod up the ramp, up to 195,000 CFM and 90 HP. This extra air bypassed the main tube entirely by being extracted from the ramp and vented on the up-stream side of the fan cowling.

 

Electro-magnetic braking plates will be located just before the fly-over rail. Should the computer system detect insufficient speed or other failure of the merging operation, the pod will automatically be stopped.

 

Additionally, sensors and software control the pod wind skirts on the entering pod and the approaching main tube pods to create an opening in the traffic and accelerate the entering pod to merge at the location and speed necessary. Reference: Entry Ramp.

 

Exit Ramps:

 

Exit ramp tubes must accept pods entering at full speed and decelerate them to a stop at the portal. When a pod enters an empty exit ramp tube, the portal gate is closed and the outlet vents along the ramp are closed. The process begins with the fly-over entry into the ramp tube as the ramp outlet vents open to allow the air in front of the pod to escape. Reference: Exit Ramp.

 

Controlled air venting and permanent magnet plates induce braking currents in the pods brake plates, bring the pod to a near stop before the portal. At this point the portal gate opens, and the pod glides out on pipe rails using a slight down-ward slope to the platform. A portal end wind screen would be needed to prevent the wind entering the platform.

 

The exit ramp can accept several pods in the ramp at a time. In this case the portal door remains open and the ramp vents react to each pod as they decelerate. This is an important feature in keeping rush-hour traffic flowing.

 

The fan cowling on the intake side is extended into the merge area where the cross-section is twice the size of a single tube. The ramp air is drawn in here through vents to fill the ramp as the pod descends without affecting the air speed in the main tube. Reference: Exit Ramp.