Nimbus B

{{Short description|U.S. meteorological satellite, lost in a launch failure}}

{{Infobox spaceflight

| name = Nimbus B

| image = Nimbus B final testing.jpg

| image_alt =

| image_caption =

| insignia =

| mission_type = Weather satellite

| operator = NASA

| COSPAR_ID = NIMBS-B

| SATCAT =

| mission_duration = Launch failure

| spacecraft_type =

| spacecraft_bus =

| manufacturer = RCA Astrospace

| dry_mass =

| launch_mass = {{convert|571.5|kg}}{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=NIMBS-B|title=Nimbus B|work=National Space Science Data Center Master Catalog|publisher=NASA Goddard Space Flight Center|access-date=June 5, 2018}} {{PD-notice}}

| dimensions =

| power =

| launch_date = {{start-date|May 18, 1968, 08:23:00|timezone=yes}} UTC{{cite web|url=https://planet4589.org/space/gcat/data/derived/launchlog.html |title=GCAT orbital launch log |first=Jonathan C. |last=McDowell |author-link=Jonathan McDowell |work=Jonathan's Space Page |access-date=November 7, 2023}}

| launch_rocket = Thorad-SLV2G Agena-D

| launch_site = Vandenberg SLC-2E

| launch_contractor =

| last_contact =

| decay_date =

| orbit_epoch = Planned

| orbit_reference = Geocentric

| orbit_regime = Low Earth

| apsis = gee

| programme = Nimbus program

| previous_mission = Nimbus 2

| next_mission = Nimbus 3

}}

Nimbus B was a meteorological satellite launched as part of the Nimbus program. It was released on May 18, 1968 from the Vandenberg Air Force Base, Lompoc, California, by means of a Thor-Agena launch vehicle, together with the SECOR 10 satellite. Nimbus B never achieved orbit because a malfunction in the booster guidance system forced the destruction of the spacecraft and its payload during launch.

The Radioisotope Thermoelectric Generator SNAP-19 RTG was salvaged from the water, refurbished and later flown on Nimbus 3.{{cite web |title=Nimbus B|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=NIMBS-B |publisher=NASA Goddard Space Flight Center|access-date=June 5, 2018}}