A Phobos-Anchored Tether for Mars Access: Downward Span, Release Velocity and Capture Budgets

This study sizes the system named in its title from stated physical relations and a stated operating basis, and reports the result as SIMULATED, NOT MEASURED. The operating principle is tether anchored on Phobos extending toward Mars, exploiting the moon's orbital motion. The Phobos tether is a civilian transport system intended to lower cargo toward Mars and receive arriving freight vehicles; it carries no payload other than transport cargo and entry capsules supplied by its users. Every performance figure is computed by the deposited script from its inputs rather than asserted, and the headline outcomes include orbital velocity of Phobos of 2135.7 metres per second; velocity of the lower tether tip in the Mars-centred frame of 1180.4 metres per second; payload velocity at the atmospheric entry interface after release of 3043 metres per second; peak entry heating relative to a direct arrival at the stated reference speed of 0.13. Mass, power, time and energy budgets are assembled from components so they can be audited line by line, off-design behaviour is discussed openly, and the limits of the sizing are stated in full. The design is presented as a civilian system throughout, with its governing constraint identified and quantified rather than merely encountered.