OTV-6

{{Short description|Longest flight of the first X-37B}}

{{Use American English|date=January 2021}}

{{Use dmy dates|date=May 2015}}

{{Infobox spaceflight

| name = USA-299

| names_list = Orbital Test Vehicle 6
OTV-6

| image = X-37B concludes sixth mission (221111-F-XX000-0002).jpg

| image_caption = X-37B that conducted OTV-6 shortly after it landed on 12 November 2022

| image_size = 300px

| mission_type = U.S. Space Force classified satellite

| operator = United States Space Force

| COSPAR_ID = 2020-029A

| SATCAT = 45606

| website =

| mission_duration = {{time interval|17 May 2020 13:14|12 November 2022 10:22|show=d}}

| spacecraft_type = Boeing X-37B

| manufacturer = Boeing

| launch_mass = {{cvt|5400|kg}}{{cite web|url=http://space.skyrocket.de/doc_sdat/x-37.htm|title=X-37B OTV 1, 2, 3, 4, 5, 6|publisher=Gunter's Space Page|date=14 January 2022|access-date=22 January 2022}}

| dimensions =

| power = Deployable solar array, batteries

| launch_date = 17 May 2020, 13:14:00 UTC

| launch_rocket = Atlas V 501 (AV-081)

| launch_site = Cape Canaveral, SLC-41

| launch_contractor = United Launch Alliance

| landing_date = 12 November 2022, 10:22 UTC

| landing_site = Shuttle Landing Facility Runway 33

| orbit_reference = Geocentric orbit

| orbit_regime = Low Earth orbit

| orbit_periapsis = {{cvt|388|km}}

| orbit_apoapsis = {{cvt|404|km}}

| orbit_inclination = 44.60°

| apsis = gee

| instruments =

| insignia =

| insignia_caption =

| insignia_size =

| programme = OTV program

| previous_mission = OTV-5

| next_mission = OTV-7

}}

USA-299, also referred to as USSF-7 and Orbital Test Vehicle 6 (OTV-6), is the third flight of the first Boeing X-37B, an American unmanned vertical-takeoff, horizontal-landing spaceplane. It was launched to low Earth orbit aboard an Atlas V launch vehicle from SLC-41 on 17 May 2020. Its mission designation is part of the USA series.

The spaceplane is operated by the Department of the Air Force Rapid Capabilities Office{{Cite web |date=2023-11-08 |title=Department of the Air Force scheduled to launch seventh X-37B mission |url=https://www.spaceforce.mil/News/Article-Display/Article/3583347/department-of-the-air-force-scheduled-to-launch-seventh-x-37b-mission/http%3A%2F%2Fwww.spaceforce.mil%2FNews%2FArticle-Display%2FArticle%2F3583347%2Fdepartment-of-the-air-force-scheduled-to-launch-seventh-x-37b-mission%2F |access-date=2023-11-30 |website=United States Space Force |language=en-US }}{{Dead link|date=July 2024 |bot=InternetArchiveBot |fix-attempted=yes }} and United States Space Force, which considers the mission classified and as such has not revealed the objectives. However an unclassified secondary satellite, FalconSat-8, was deployed from the X-37B soon after launch.{{cite web|url=https://space.skyrocket.de/doc_sdat/falconsat-8.htm|title=FalconSat 8 |publisher=Gunter's Space Page|access-date=2020-09-18}}