Solar Outpost 1 (SU1) was located very close to the sun to study the solar radiation. Due to the close proximity to the sun, it would be difficult to cool a large self supporting station. Instead a smaller station was designed that required regular replenishment of 02 and C02 scrubbers. A sister station, Solar Outpost 2, was constructed to resupply SU1. Solar Outpost 2 (SU2) was located further from the sun where cooling was not a problem.
The transfer of supplies between SU1 and SU2 was originally intended to be done through a precise alignment of the two stations. The ATV transfer vehicle would use the momentum from undocking from one station to carry it across the 100 unit distance to the other station. Because the two stations were precisely aligned, no fuel would be required to re-orient the ATV or to accelerate or break it.
Unfortunately, maintaining this precise alignment proved difficult. Several times the ATV missed the docking connection and knocked the station even further out of alignment. Procedures were then changed to manually pilot the ATV shuttle between the stations instead of relying on an unattended transfer. This caused concern as the fuel supplies began to run down faster than planned.
However it was not the lack of fuel, but a gravity fluctation, that struck the fatal blow to this pair of stations. Solar Outpost 1 was positioned very close to the sun, its science module inside the circle of influence, while the living quarters and radiators kept the station anchored just outside of the sun's orbit. A a gravity fluctuation caused SU1 to be tugged slightly closer to the sun and out of its stable location. Being a minimal station, SU1 did not have any propulsion modules.
The ATV shuttle was immediately launched from SU2 to try to bring SU1 back to a stable location. It was not able to reach SU1 before it was pulled into the sun's orbit. The ATV shuttle was already low on fuel because of the change in docking procedures. The shuttle did not have enough fuel to exit the sun's orbit. The crew was forced to abort their mission and watch helplessly as SU1 and the two scientist on board fell into the sun.
The destruction of SU1 led the the eventual abandonment of SU2 since the two stations were designed to work as a pair.