On September 15, 1951, a Soviet rocket was set to launch when one of its two canine passengers was nowhere to be found. Bobik, a dog assigned to that day's flight from the Kapustin Yar test range, had escaped from the site. NASA's history office, which documents this Soviet-era program alongside America's own, says the launch couldn't wait, so a technician found a stray dog wandering near the base canteen and brought her in as a last-minute substitute. They called her ZIB, short for the Russian phrase meaning "Substitute for Missing Dog Bobik." Within hours, she was strapped in and launched.A missing dog and an unplanned substituteZIB had no training and had never been inside a capsule until the morning of her launch. Nevertheless, the launch was carried out successfully with ZIB being placed inside the pressurized cabin in the place of Bobik. According to NASA, the rocket flew at about 100 kilometers above the Earth's surface, and both dogs parachuted safely back to Earth. It remains one of the stranger footnotes in early spaceflight history: a stray that wandered into a science experiment and survived. Bobik, meanwhile, never got the chance to fly at all; NASA's history does not say what became of him after he ran off.Why the Soviets trusted street dogs over show dogsZIB's sudden recruitment was not as rash as it sounds, since the Soviet scientists had based their entire space dog program on this very type of animal. In 2017, a study titled 'What the dogs did: animal agency in the Soviet manned space flight programme,' published in BJHS Themes, a peer-reviewed journal from the British Society for the History of Science, found that researchers intentionally targeted mixed-breed female strays that weighed up to six or seven kilograms and were typically taken from the streets of Moscow rather than brought up as pedigreed pets. ZIB was an exception to that usual practice, with no time to bring a trained Moscow-sourced dog to the remote Kapustin Yar site, technicians grabbed the nearest available stray instead. The study found that female dogs were chosen throughout the program partly because their anatomy made it easier to fit the sanitation equipment built into the suits and capsules. Researchers preferred stray dogs as they were hardy and used to looking after themselves, and the study noted that scientists even went for light colored coats because they showed up better on the in-flight cameras. That is why a healthy stray picked up near the canteen could serve as well as a dog bred for the mission in a pinch.Laika's one-way flight aboard Sputnik 2 in 1957 followed the same program that sent ZIB into the sky. Image Credits: NASAA program built on trial, error, and heartbreakNASA's records indicate that the Soviet R-1 rocket series carried nine dogs on test flights in 1951 and 1952, with some flying more than once. Not all missions ended as gently as ZIB’s. Earlier in the month, two dogs, Dezik and Lisa, died when the parachute on their capsule would not open. Another pair, Smelaya and Malyshka, had their own drama when Smelaya bolted the night before launch and reappeared a day later, echoing ZIB's last-minute swap. The early bumpy flights were stepping stones to Laika’s one-way ride on Sputnik 2 in 1957, and then to Yuri Gagarin becoming the first human in orbit in 1961.How ethical standards eventually caught upDecades later, NASA became the first American federal agency to officially document bioethics guidelines about animal research. In an interview archived by NASA, the space agency's first Chief Veterinary Officer, Joseph Bielitzki, said the guiding concepts behind those rules were respect for life, societal benefit, and non-maleficence, or keeping distress to a minimum wherever possible. The standards came long after the Soviet dog flights of the early 1950s and were never applied to them. They still show how much thought on this subject has changed since a stray was scooped up from near a launch pad canteen and sent skyward within hours.Why ZIB's story still resonatesThere is something strangely human about the story of ZIB. It sounds like an urban legend: a random stray, a mistaken identity, and a trip she never saw coming. But it did happen, and it is right there in NASA's own archives. Over seventy years later, ZIB's short flight is a reminder that some of the very first forays into human spaceflight were done by animals who had no idea what they were signing up for, and, in Bobik's case, one who never got the chance at all.