Zond 5

01Mission facts

02Mission timeline

1. 2 Sep 1968

   Two flight tortoises sealed aboard; feeding stops so spaceflight effects can be isolated

2. 14 Sep 1968

   21:42 UTC (15 Sep Moscow time): launch from Baikonur Site 81/23 on Proton-K; Blok D restart sends it moonward about 67 minutes later

3. 17 Sep 1968

   03:11 UTC: midcourse correction at 325,000 km using backup Sun/Earth sensors after the 100K star tracker fails from contamination

4. 18 Sep 1968

   Loops 1,950 km above the lunar far side on a free-return trajectory; photographs the Moon and Earth

5. 19 to 20 Sep 1968

   Jodrell Bank hears a Russian voice calling out instrument values from the returning craft, a comms rehearsal that briefly reads as a crewed flight

6. 21 Sep 1968

   16:08 UTC: ballistic reentry into the backup zone; splashdown in the Indian Ocean at 32 deg 38 min S, 65 deg 33 min E; first successful circumlunar return

7. 3 Oct 1968

   Recovery ship Vasiliy Golovnin delivers the capsule to Mumbai (Bombay) for return to the USSR

8. 7 to 11 Oct 1968

   Tortoises reach Moscow Oct 7; dissection Oct 11 finds changes driven by their 39-day fast, not spaceflight

9. 21 to 27 Dec 1968

   Apollo 8, greenlit partly on fear of a crewed Zond, orbits the Moon with humans aboard

Teal dots: events that physically happened in flight or on the Moon. Grey: announcements, namings, contracts, and targets.

03The mission

Zond 5 was not a science probe wearing a disguise; it was a dress rehearsal for putting cosmonauts around the Moon. The spacecraft was a Soyuz 7K-L1 (vehicle no. 9L, about 5,375 kg), a Soyuz descent module and service module with the orbital module deleted so a Proton-K with a Blok D upper stage could throw it to the Moon. Three previous L1 circumlunar attempts had failed on ascent, so this fourth try only received the public name "Zond 5" after the Blok D restarted about 67 minutes into the flight and sent it out of its 191 x 219 km parking orbit toward the Moon on September 14, 1968 (21:42:11 UTC liftoff from Baikonur's Site 81/23).

Riding inside the descent module was a small ark: two steppe tortoises (Horsfield's tortoises, 0.34 to 0.40 kg each, ages 6 to 7, sealed aboard on September 2 and fasted from that day so spaceflight effects could be isolated), hundreds of Drosophila fruit-fly eggs, air-dried cells of wheat, barley, peas, carrots and tomatoes, a flowering Tradescantia, three strains of chlorella algae, and a bacterial culture. Six control tortoises stayed on the ground. The flight was not smooth: the 100K star tracker failed almost immediately from surface contamination, and controllers had to fly the September 17 midcourse correction (at 325,000 km out) on cruder Sun and Earth sensors. On September 18 Zond 5 swung 1,950 km above the lunar far side and headed home on its free-return trajectory, photographing the Moon and shooting high-quality pictures of Earth from about 90,000 km away.

On the night of September 19-20, Jodrell Bank Observatory heard something startling from the returning spacecraft: a Russian voice calling out instrument readings. West German listeners at Bochum picked it up too. It was a communications test, a recorded or ground-relayed cosmonaut voice played through the spacecraft's radio link to rehearse a future crewed flight, but at the height of the Moon race it read as evidence that Soviet crews were about to fly, and Western observers initially took the mission as proof a crewed circumlunar flight was imminent.

The ending was survivable but not the one Moscow wanted. On the return leg the 101K Earth sensor also failed, the guidance platform shut off the guided-skip reentry system, and controllers had to hand-steer the reentry attitude with the one remaining Sun sensor. Instead of the planned guided reentry to a recovery on Soviet territory, Zond 5 flew a direct ballistic reentry into the backup zone and splashed down in the Indian Ocean at 32 deg 38 min S, 65 deg 33 min E at 16:08 UTC on September 21, 1968, about 105 km from the nearest Soviet tracking ship, after a mission of 6 days, 18 hours and 24 minutes. Soviet vessels Borovichy and Vasiliy Golovnin recovered the capsule, which reached Mumbai (then Bombay) on October 3 for the trip home.

The tortoises survived, arriving in Moscow on October 7. Dissection on October 11, after what was by then a 39-day fast, found the main changes were caused by starvation rather than the trip around the Moon: as animal test results go, a green light. Zond 5 was the first successful circumlunar mission by any nation, and together with reconnaissance photos of the giant N-1 rocket at Baikonur it sharpened NASA's fear of being beaten, feeding the decision to send Apollo 8 into lunar orbit that December. The race verdict is part of the story too: no cosmonaut ever flew a Zond around the Moon, and the L1 program wound down after Apollo 8 and Apollo 11 made it moot.

04In pictures

Tap a photo to enlarge.

05Sources

• Siddiqi, Beyond Earth: A Chronicle of Deep Space Exploration 1958-2016 (NASA SP-2018-4041), Zond 5 entry pp. 79-80
• NASA History, 50 Years Ago: On the Way to the Moon (Zond 5 retrospective)
• NASA Science, Zond 5 resource page (its hosted spacecraft photo is credited 'S.P. Korolev RSC Energia': third-party copyright merely hosted by NASA, not public domain, do-not-self-host tier per the licensing policy)
• Jodrell Bank Centre for Astrophysics, history of early space tracking, part 2 (Zond 5 voice intercept and reentry timing)
• Wikipedia, Zond 5 (recovery ships, tortoise weight loss, launch time cross-check)

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