View source for Zond 4

{{Short description|1968 Soviet test spaceflight}}
{{Use dmy dates|date=May 2020}}
{{Infobox spaceflight
| name                  = Zond 4
| names_list            = Soyuz 7K-L1 s/n 6

<!--image of the spacecraft/mission-->
| image                 = Zond L1 drawing.svg
| image_caption         = <!--image caption-->
| image_alt             = <!--image alt text-->
| image_size            = 125px
<!--Basic details-->
| mission_type          = [[The Moon|Lunar]] flyby<br/>Spacecraft test
| operator              = [[OKB-1]]
| Harvard_designation   = <!--spacecraft launched 1962 and earlier only (eg. 1957 Alpha 2)-->
| COSPAR_ID             = 1968-013A
| SATCAT                = 03134
| website               = <!--Homepage of the craft/mission, OFFICIAL PAGES ONLY-->
| mission_duration      = <!--How long the mission lasted-->
| distance_travelled    = <!--How far the spacecraft travelled (if known)-->
| orbits_completed      = <!--number of times the spacecraft orbited the Earth - see below for spacecraft beyond Earth orbit-->
| suborbital_range      = <!--downrange distance reached if spacecraft did not enter orbit-->
| suborbital_apogee     = <!--altitude reached if spacecraft did not enter orbit-->

<!--Spacecraft properties-->
| spacecraft            = <!--Spacecraft name/serial number (eg. Space Shuttle ''Discovery'', Apollo CM-118), etc-->
| spacecraft_type       = <!--eg. GPS Block II, Kobalt-M, US-K, etc-->
| spacecraft_bus        = [[Soyuz 7K-L1]]
| manufacturer          = [[OKB-1]]
| launch_mass           = {{convert|4,425|kg}}
| BOL_mass              = <!--spacecraft mass in orbit at beginning of operational life, after LEOP phase-->
| landing_mass          = <!--Mass after landing (recovered spacecraft only)-->
| dry_mass              = <!--spacecraft mass in orbit without fuel-->
| payload_mass          = <!--Mass of cargo carried by spacecraft (eg. for Space Shuttle), or total mass of instrumentation/equipment/experiments for mission-->
| dimensions            = 4.5 m x 2.2 m x 2.72 m
| power                 = <!--end-of-life power, in watts-->

<!--Launch details-->
| launch_date           = 2 March 1968, 18:29:23 UTC
| launch_rocket         = [[Proton-K]]/[[Block D|D]]
| launch_site           = [[Baikonur Cosmodrome|Baikonur]] [[Baikonur Cosmodrome Site 81|81/6]]
| launch_contractor     = <!--organisation(s) that conducted the launch (eg. United Launch Alliance, Arianespace, etc)-->
| deployment_from       = <!--place where deployed from-->
| deployment_date       = <!--date deployed-->
| entered_service       = <!--date on which the spacecraft entered service, if it did not do so immediately after launch-->
<!-- * - e.g. Proton-M/Briz-M not Proton-M, but Titan IV(401)A not Titan IV(401)A-Centaur-->

<!--end of mission-->
| disposal_type         = deorbited/destroyed
| deactivated           = <!--when craft was decommissioned-->
| destroyed             = <!--when craft was destroyed (if other than by re-entry)-->
| last_contact          = <!--when last signal received if not decommissioned-->
| recovery_by           = <!--recovered by-->
| recovery_date         = <!--recovery date-->
| decay_date            = {{end date|1968|03|09|df=yes}}
| landing_date          = <!--when the spacecraft made a controlled landing, not needed if it did not return intact-->
| landing_site          = 
<!--
    The following template should be used for ONE of the three above fields "end_of_mission", "decay" or "landing" if the spacecraft is no longer operational.
    If it landed intact, use it for the landing time, otherwise for the date it ceased operations, or the decay date if it was still operational when it re-entered.
    {{end date|YYYY|MM|DD|hh|mm|ss|TZ=Z}} (for Zulu/UTC) or {{end date|YYYY|MM|DD}} (if time unknown) 
-->

<!--orbit parameters-->
<!--as science-related articles, SI units should be the principal units of measurement, however we usually use {{convert}} to display imperial units in parentheses after the initial values-->
| orbit_reference       = [[Geocentric orbit|Geocentric]]
| orbit_regime          = [[Elliptical orbit]] 
| orbit_longitude       = <!--geosynchronous satellites only-->
| orbit_slot            = <!--Designation of orbital position or slot, if not longitude (e.g plane and position of a GPS satellite)-->
| orbit_semimajor       = <!--semimajor axis-->
| orbit_eccentricity    = <!--orbital eccentricity-->
| orbit_periapsis       = {{convert|200|km|mi}}
| orbit_apoapsis        = {{convert|400000|km|mi}}  
| orbit_inclination     = 51.53° 
| orbit_period          = 
| orbit_RAAN            = <!--right ascension of the ascending node-->
| orbit_arg_periapsis   = <!--argument of perigee/periapsis-->
| orbit_mean_anomaly    = <!--mean anomaly at epoch, only use in conjunction with an epoch value-->
| orbit_mean_motion     = <!--mean motion of the satellite, usually measured in orbits per day-->
| orbit_repeat          = <!--repeat interval/revisit time-->
| orbit_velocity        = <!--speed at which the spacecraft was travelling at epoch - only use for spacecraft with low orbital eccentricity-->
| orbit_epoch           = <!--the date at which the orbit parameters were correct-->
| orbit_rev_number      = <!--revolution number-->
| apsis                 = gee

<!--transponder parameters-->
| trans_band            = <!--Transponder frequency bands-->
| trans_frequency       = <!--specific frequencies-->
| trans_bandwidth       = <!--bandwidth-->
| trans_capacity        = <!--capacity of the transponders-->
| trans_coverage        = <!--area covered-->
| trans_TWTA            = <!--TWTA output power-->
| trans_EIRP            = <!--equivalent isotropic power-->
| trans_HPBW            = <!--half-power beam width-->

<!--Only use where a spacecraft/mission is part of a clear programme of sequential missions. 
If in doubt, leave it out-->
| programme             = [[Zond program|Zond]]
| previous_mission      = [[Zond 1967B]]
| next_mission          = [[Zond 1968A]]

<!--mission insignia or patch-->
| insignia              = <!--omit the "file" prefix-->
| insignia_caption      = <!--image caption-->
| insignia_alt          = <!--image alt text-->
| insignia_size         = <!--include px/em; defaults to 180px-->
}}

'''Zond 4''', part of the Soviet [[Zond program]] and an uncrewed version of [[Soyuz 7K-L1]] crewed Moon-flyby spacecraft, was one of the first Soviet experiments towards crewed circumlunar spaceflight. It was launched to test the [[spaceworthiness]] of the new capsule and to gather data about flights in [[circumterrestrial space]]. It was the first Soviet spacecraft to possess a computer, the 34&nbsp;kg Argon 11.<ref name="huntress-description">{{cite book|last1=Huntress|last2=Marov|title=Soviet Robots in the Solar System: Mission Technologies and Discoveries|url=https://books.google.com/books?id=rgl_C0XrKTUC|publisher=Springer New York|year=2011|page=172|isbn=9781441978981 }}</ref>

The spacecraft was successfully launched by a Proton D-1e on 2 March 1968 into a 400,000&nbsp;km apogee orbit 180 degrees away from the Moon.<ref>{{cite book|title=Almanac of Soviet Space Flight|first=Dennis |last=Newkirk|year=1990 |url=https://books.google.com/books?id=QpdTAAAAMAAJ
|page=67|publisher=Gulf Publishing Company|isbn=9780872018488 |access-date=February 10, 2023}}</ref> It was launched away from the Moon probably to avoid trajectory complications with lunar gravity. However, on re-entry the L1's guidance system failed. It hit the atmosphere precisely at the calculated time, but was not guided to generate lift and fly out of the atmosphere again. A ballistic re-entry would mean no recovery on Soviet soil, so the APO destruct system automatically blew up the capsule at 10 to 15&nbsp;km altitude, 180–200&nbsp;km off the [[Africa]]n coast at [[Guinea]].<ref name="huntress-description"/>

The Zond 4 flight was in some ways similar to the American [[Apollo 4]] and [[Apollo 6|6]] missions as they were uncrewed test flights in highly elliptical Earth orbits.<ref>{{cite web|title=50 Years Ago: Zond 4 launched successfully|first=Michael|last=Wong|date=March 6, 2018|url=https://www.nasa.gov/feature/50-years-ago-zond-4-launched-successfully/|publisher=NASA|access-date=February 10, 2023|archive-date=8 February 2023|archive-url=https://web.archive.org/web/20230208134321/https://www.nasa.gov/feature/50-years-ago-zond-4-launched-successfully/|url-status=dead}}</ref>

== References ==
{{Reflist}}

== External links==
{{Portal|Spaceflight}}
* [https://web.archive.org/web/20120705074647/http://www.astronautix.com/project/lunarl1.htm Astronautix.com Information on Lunar L1 program, including Zond 4]

{{Orbital launches in 1968}}
{{Zond program}}
{{N1-L3}}

[[Category:Zond program]]
[[Category:Spacecraft launched in 1968]]
[[Category:1968 in the Soviet Union]]