A technical problem could delay SpaceX's launch plans

An electrical distribution unit aboard the International Space Station malfunctioned on Monday, blocking two of the lab's eight supply channels. The crew is not in danger while the engineers solve the problem, said officials, but if it can not be resolved, the electrical box in question may have to be replaced by a spare box, this which could eventually prompt NASA to delay the launch of a SpaceX Dragon supply ship. Wednesday.

Assuming a punctual launch at the top of a Falcon 9 rocket, the Dragon cargo capsule, loaded with nearly 5,000 kg of equipment and supplies, is expected to catch up with the station early Friday and stay in place while the robot's arm laboratory locks and pulls out. it is for berthing.

The Canadian-built robotic arm can operate with only one power source, but NASA's flight rules require two redundancies. It turned out that one of the two power circuits supporting the operation of the arms was turned off by the problem of the main bus switching unit that broke out on Monday.

During an outing in space in 2012, Sunita Williams, seen here, and Aki Hoshide, out of sight, completed the installation of a switchgear replacement main bus, or MBSU, one of which is visible at the bottom right. Four MBSUs distribute electrical energy from the station's solar panels via eight power channels. An MBSU malfunctioned Monday, blocking two of these channels. Engineers are studying how to reorient this power in the short term. Spare parts are available if the MBSU needs to be replaced.

NASA

A NASA official said that the power supply of the two channels powered by the main bus switching unit, MBSU, could be re-routed using jumpers, but it was not possible to use the power supply. was not clear if this included feeding the robot's arm. NASA flight rules require redundant power for robot arm operations. If the secondary power supply can not be re-routed or reinstated, and if the flight rule remains in effect, the launch of the Dragon would likely be delayed until the MBSU can be replaced. , robotic way or when going out into space.

The primary solar power system of the space station consists of four rotating solar wings, two to the right of the pressure modules of the outpost and two to the left. Four MBSUs, mounted in the center of the station's solar panel structure, distribute the energy of the downstream panels to various electrical circuits. The MBSU that malfunctioned cut the power channels 3A and 3B. The system has been designed so that channels can be "interconnected" as needed to circumvent failures.

In 2017, an MBSU fueling the 2A and 2B channels was malfunctioning, prompting the flight controllers to replace it with the help of the station's robot arm. Another MBSU was replaced during two spacewalks in 2012.