MOSCOW, Russian Federation. A Russian spacecraft that broke down on its way to the International Space Station last week will fall to Earth by midday on Friday, according to European Space Agency officials.
The uncrewed Progress 59P cargo vessel has been tumbling around the planet at about 17,000mph since it reached orbit last Tuesday. With all hope of recovering the spacecraft now lost, the capsule and its cargo are destined to tear into the atmosphere late on Thursday night (UK time) at the soonest.
Scientists tracking the stricken vessel with ground radar said 20-40% of the spacecraft could survive the intense heat of re-entry. The most likely part to withstand the inferno, at least partially, is the capsule’s docking mechanism, a sturdy 200kg metal ring the size of a rear tractor wheel.
Fully laden at launch, the vessel weighed 7,300kg, including more than a tonne of fuel and 2.5 tonnes of cargo. On that basis, between 750kg and 1.5 tonnes of the spacecraft body may survive re-entry and strike Earth. The debris is most likely to fall into the ocean or hit remote, unpopulated land.
The spacecraft’s orbit varies from 51.6 degrees north to 51.6 degrees south, so charred fragments of the spacecraft could land in any region within those latitudes. The trajectory puts Edgware in London as one of the most northerly parts of Britain that is potentially at risk of falling debris.
But Holger Krag, head of the EuropeanSpace Agency’s space debris office in Darmstadt, said the risk of anyone anywhere in the world being hit by falling parts of the Progress vessel were extremely remote. In six decades of spaceflight, no one has ever been hit by falling space hardware, he said.
“It doesn’t all come down in one piece. Most of the destruction happens between 80km and 70km high, and a very limited number of components have the potential to survive. These are scattered over a huge distance, up to 1000km, so you might find a single piece every 100km or so,” Krag told the Guardian.
At its most northerly pass, Progress is travelling west to east, so if it re-entered the atmosphere over Britain, charred fragments could conceivably fall in a broad line from Cardiff, through Bristol and Slough, to London and onwards to Southend-on-Sea.
More likely spots for debris to fall are the Pacific, Atlantic and Indian oceans. On its route over these, the spacecraft passes above much of North and South America, continental Europe, Africa, India, China, Malaysia and Australia.
Every year 100 tonnes of space hardware re-enter the atmosphere, with the majority of it burning up before it hits the planet. Defunct satellites and spent rocket bodies fall to Earth every week. Larger items, such as the Progress cargo vessel, re-enter roughly once a year.
The spacecraft circles the Earth every 90 minutes and on Thursday morning still had about a dozen laps to complete before it entered the atmosphere.
Space agencies in the US, Europe and Russia have been tracking the spacecraft, but its tumbling motion, speed and altitude mean there are substantial uncertainties over where and when it will come down. “We expect re-entry to happen some time from late Thursday evening to midday on Friday,” Krag said.
As the Progress vessel spirals down into the atmosphere it will undergo a massive deceleration from its orbital speed to about 180mph. Friction with the atmosphere will cause the spacecraft to heat up and break apart. Aluminium components will melt quickly, but stainless steel and titanium components will last longer.
The fireball could be bright enough to see in broad daylight, Krag said. But with more than 70% of the Earth’s surface covered by water, and only 3% of the land heavily populated, the chances are slim that anyone will witness it, let alone be struck by debris.
“It’s a complete waste of time to worry about this. There are daily risks that are much higher,” Krag said from his office at latitude 49.8 degrees north. “The risks of driving a car or flying in a plane are higher. Your chance of being struck by lightning is higher.”
Progress was designed to be a disposable cargo ship. In normal operations, it docks with the space station, is unloaded by the crew, and then jettisoned in a controlled re-entry over the Pacific to ensure any debris falls into the ocean. Because Russian space agency engineers have no control over the Progress module, they cannot purposely steer it into the ocean.
The vessel, carrying food, water and clothing to the space station, overshot its intended orbit on Tuesday and failed to establish communications with Russian ground controllers. An investigation into the cause of the malfunction is underway.
Only in its final hours will scientists have a clearer idea of where and when the spacecraft will re-enter the atmosphere. But even then, it will be impossible to issue any precise warnings. “You can do nothing about it. We are not able to give any reasonable warning,” Krag said.
The European Space Agency’s predictions are based on re-entries of other spacecraft, because its scientists do not have the precise details of the materials and masses of the components used in the Russian spacecraft.
Credit: Guardian UK
