The SKR4 was a space recovery vehicle shown in the episode "Inferno." It had a crew of two, a pilot and a navigator. The ship was preparing to rendezvous with a malfunctioning rocket when a meteorite collided with the vessel. Aborting the mission on the pretence of a mechanical fault, a Mysteron reconstruction of the SKR4 changed course and reset its coordinates for Earth. Meanwhile, the Mysterons had revealed the target of their next threat: the Najama desalinisation plant in the foothills of the Andes Mountains, which processed seawater for irrigating the interior of South America. Colonel White dispatched a team, led by Captain Scarlet and Captain Blue, to set up observation points in the Najama Valley while the service personnel are evacuated. Setting up a base in an old Aztec temple, Captain Scarlet and Captain Blue alternated the night watch, but a curious scraping sound awoke Captain Blue rather rudely. The officers were unaware that Captain Black had infiltrated the temple and placed a strange device in a giant statue of the Aztec Sun God.
Elsewhere, Euro Tracker station was monitoring the SKR4's return to Earth. When the spacecraft failed to respond to transmissions, Major Moran contacted Spectrum. A radio signal interfered with the SKR4's re-entry systems, altering its projected landing area. Learning from Lieutenant Green that the signal was transmitting from Najama and that the SKR4 was carrying several explosive packs, Colonel White deduced that the spacecraft would be guided to crash into the Najama Valley. As the SKR4 began re-entry, the Spectrum team frantically tried to pinpoint the exact location of the transmitter--the device that Captain Black had planted. With only minutes remaining till impact, Captain Blue discovered that it was somewhere inside the temple, and Captain Scarlet ordered the Spectrum Angels to attack. Eventually, even the statue was destroyed in the bombardment, but too late to stop the SKR4 crashing into the wreckage. The explosion triggered a landslide which surged into the valley, striking vulnerable liquid oxygen tanks and annihilating the Najama complex in a series of massive explosions. Thousands of square miles of South America were now set to revert to arid wasteland.
- Space cruising speed: 19,600 mph
- Escape velocity: 25,000 mph
- Crew: 2