An out-of-control Chinese space station with “highly toxic” chemicals on board could hit a number of major world cities, including Christchurch, research suggests.
China’s first prototype station, Tiangong-1, will come crashing back to the planet between March 30 and April 6, experts say.
It has the highest chance of crashing into cities along a narrow strip around latitudes of 43 degrees north and south.
As well as Christchurch, this includes a number of highly populated cities including New York, Barcelona, Beijing, Chicago, Istanbul, Rome and Toronto.
It is most likely to hit these places because it is travelling parallel to the equator at the most northern and southern points of its orbit, the Daily Mail reports.
From our perspective on Earth it appears to be travelling more slowly above these regions, thanks to its geometry relative to the Earth, although its speed actually remains constant.
Because it takes longer to cross the surface of the Earth at these latitudes it has a higher risk of coming down here.
The doomed 8.5-tonne craft, which has been hurtling towards Earth since control was lost in 2016, is believed to contain dangerous hydrazine.
Scientists will only know the precise date it will impact and exactly where debris will fall during the finals weeks of its decline.
Explaining why this is so Dr Hugh Lewis, senior lecturer in Aerospace Engineering at the University of Southampton, compared the geometrical processes at work to crossing the road.
Speaking to MailOnline, he said: “The spacecraft is travelling around a more or less circular orbit, which is tipped with respect to the equator at 43°.
“If you plot this path on a map of the Earth, it produces a sine wave pattern, with the slower curve of the wave in northern and southern latitudes and the faster straighter sections running from east to west.
“If you imagine the green low risk area on the map is the part of the road we’re trying to walk across, the quickest way is to go at 90 degrees – straight across.
“When the spacecraft crosses the equator, it’s crossing the road at this point, and it does so really fast.
“When it goes across the red bands further north and south, it’s crossing at a steeper angle – almost parallel to the road.
“It takes longer to cross at these latitudes, which is why it has a higher risk of coming down here.”
Predictions of Tiangong-1’s most likely point of impact come from Aerospace, a US research organisation based in El Segundo, California, that advises government and private enterprise on space flight.
It says the space station will enter the Earth’s atmosphere on April 4, give or take a week, and debris will fall no further north than 42.7° N latitude or south of 42.7° S latitude.
These zero probability areas, marked safe as Tiangong-1 does not fly over them, constitute about a third of the Earth’s total surface area….
“Hydrazine is highly toxic and dangerously unstable in the anhydrous form. According to the U.S. Environmental Protection Agency:
Symptoms of acute (short-term) exposure to high levels of hydrazine may include irritation of the eyes, nose, and throat, dizziness, headache, nausea, pulmonary edema, seizures, coma in humans. Acute exposure can also damage the liver, kidneys, and central nervous system. The liquid is corrosive and may produce dermatitis from skin contact in humans and animals. Effects to the lungs, liver, spleen, and thyroid have been reported in animals chronically exposed to hydrazine via inhalation. Increased incidences of lung, nasal cavity, and liver tumors have been observed in rodents exposed to hydrazine.
“Few cases of pure hydrazine exposure have been reported in the medical literature.” The usual antidote is vitamin B6 or the related pyridoxine.
Limit tests for hydrazine in pharmaceuticals suggest that it should be in the low ppm range.
At least one human is known to have died after 6 months of sublethal exposure to hydrazine hydrate. The U.S. National Institute for Occupational Safety and Health has prepared a Skin Notation Profile evaluating and summarizing the literature regarding the hazard potential of hydrazine, and has developed criteria for a recommended standard for occupational exposure.”