The answer to LTT-14 is two supply ships are needed to support the main cable laying ship.
The main cable laying ship (M), and two supply ships (S1 & S2) all leave Porthcurno at the same time, with full tanks of fuel. At the 1/6 way point on the circumference of the Globe, S1 refuels M with a 1/3 of its fuel, so it has just enough fuel to return back to Porthcurno. Meanwhile M and S2 continue until they reach the 1/4 way point of the circumference of the Globe. At this point, S2 refuels M, so it has a full tank of fuel and can sling shot around the Globe from 1/4 to 3/4 way point. S2 then turns around and heads back towards Porthcurno, and refuels with S1 at the 1/12 way point. Both S1 and S2 have enough fuel to head back together towards Porthcurno, where they both refuel and then head out in the opposite direction towards the 3/4 way point to rendezvous with M. At the 5/6 way point, S1 refuels S2, so it has a full tank of fuel to continue towards the 3/4 way point to meet up with M, while S1 returns to Porthcurno to refuel. S2 continues on and meets M at the 3/4 way point and refuels it, so M can return back to Porthcurno. S1 returns to the 11/12 way point and refuels S2, which now has more than enough (surplus) fuel to return back to Porthcurno.
As an additional part to the question, how much further could the main supply ship travel after the last rendezvous? After S1 & S2 have refuelled at 11/12 way point, there is half a tank of surplus fuel left or enough to travel 1/4 circumference around the globe.
Congratulations to Derek Burgess for providing the winning answer. Educated at Cambridge University in the UK, Derek is a software engineer specializing in embedded systems in the digital broadcasting arena, having dabbled in telephony based speech recognition systems en route.
Derek will receive a copy of our book, Revenue Assurance: Expert Opinions for Communications Providers.