Progress 21

{{Short description|Soviet unmanned Progress cargo spacecraft}}

{{Use British English|date=December 2020}}

{{Use dmy dates|date=December 2020}}

{{Infobox spaceflight

| name = Progress 21

| image = Progress drawing.svg

| image_caption = A Progress 7K-TG spacecraft

| mission_type = Salyut 7 resupply

| COSPAR_ID = 1984-042A

| SATCAT = 14961{{cite web|url=http://planet4589.org/space/log/launchlog.txt|title=Launchlog|work=Jonathan's Space Report|access-date=5 December 2020}}

| spacecraft = Progress (No.116)

| spacecraft_type = Progress 7K-TG{{cite web|url=https://space.skyrocket.de/doc_sdat/progress.htm|title=Progress 1 - 42 (11F615A15, 7K-TG)|work=Gunter's Space Page|access-date=5 December 2020}}

| manufacturer = NPO Energia

| launch_date = 7 May 1984, 22:47:15 UTC

| launch_rocket = Soyuz-U

| launch_site = Baikonur, Site 31/6

| docking =

{{Infobox spaceflight/Dock

| docking_target = Salyut 7

| docking_type = dock

| docking_port = Aft{{cite web|url=http://space.kursknet.ru/cosmos/english/cargoes/pr21.sht|title=Cargo spacecraft "Progress 21"|work=Manned Astronautics figures and facts |archive-url=https://web.archive.org/web/20071013000239/http://space.kursknet.ru/cosmos/english/cargoes/pr21.sht|archive-date=13 October 2007}}

| docking_date = 10 May 1984, 00:10 UTC

| undocking_date = 26 May 1984, 09:41 UTC

}}

| disposal_type = Deorbited

| decay_date = 26 May 1984, 15:00:30 UTC

| orbit_epoch = 26 May 1984

| orbit_reference = Geocentric

| orbit_regime = Low Earth

| orbit_periapsis = 187 km

| orbit_apoapsis = 246 km

| orbit_inclination = 51.6°

| orbit_period = 88.8 minutes

| apsis = gee

| programme = Progress (spacecraft)

| previous_mission = Progress 20

| next_mission = Progress 22

}}

Progress 21 ({{Langx|ru|Прогресс 21|italic=yes}}) was a Soviet uncrewed Progress cargo spacecraft, which was launched in May 1984 to resupply the Salyut 7 space station.