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ULA to Launch 'STP-3' Mission

By Jon Reino

UPDATE 12/7: After leaving an additional day to assess repairs to the leaking propellant tank, 'STP-3' successfully launched at 5:19 a.m. EST after delaying for just over an hour due to high altitude winds. To view or photo coverage click here.

UPDATE 12/5: During initial operations, a leak was discovered in the Rocket Propellant-1 (RP-1) ground storage system. Launch is now scheduled for Mon., Dec. 6 at 4:04 a.m. EST with a two-hour window.

ULA and the 45th Space Wing are currently targeting 4:04am EST (0904 UTC) for the launch of the 'Space Test Program-3 (STP-3)' mission. The powerful Atlas V 551 rocket will carry a diverse rideshare payload for the US Space Force, the National Nuclear Security Administration, and NASA.

The 'STP-3' payload fairing is hoisted during final vehicle processing. (Photo: ULA)


'STP-3' will launch from Space Launch Complex-41 at Cape Canaveral Space Force Station, Florida. The Atlas V 551 that will carry it is the most powerful configuration for the first stage of the United Launch Alliance's (ULA) flagship rocket, which most recently carried the 'LUCY' mission for NASA on October 16th in the 401 configuration. The numbers following the Atlas V name correspond to the configuration of its payload fairings, the number of strap-on Solid Rocket Boosters (SRBs), and the upper stage model. In this instance, "551" indicates a 5.4 meter fairing, 5 SRBs, and a single-engine Centaur Upper Stage. Other configurations include a 4 meter fairing or no fairing when flying the Boeing 'Starliner CST-100', no SRBs or as many as 5, and a dual-engine Centaur. The 551 that will be launching 'STP-3' can carry up 8,900 lbs of payload to geostationary transfer orbit and generates 3,827 kN (860,000 lbf) of thrust at sea level.

The Atlas V rocket continues the heritage of the Atlas family of Intercontinental Ballistic Missiles (ICBMs) developed by the Convair Division of General Dynamics in the 1950's for the U.S. Air Force. Known as the SM-65 Atlas, they carried NASA's Mercury missions 6-9, beginning with John Glenn's February 20th,1962 flight making him the first American to orbit the Earth. The Atlas V has completed 89 successful launches to date since debuting in 2002, with only one of them considered a partial failure during the launch of the 'USA-194' mission for the National Reconnaissance Office. The Atlas did not deliver the payload to its specified orbit; however, the spacecraft was able to compensate, and the mission is still considered a success. ULA is a joint venture between aerospace giants Lockheed Martin and Boeing formed in 2006.

This mission will utilize a unique payload fairing, the first of a new manufacturing technique to be flown. Using a process called "Out-of-Autoclave (OoA)" manufacturing, the fairing is manufactured in two complete halves made using a process to cure carbon fiber composites using only an oven, rather than 18 or more separate pieces pressed together in an autoclave as was used in the previous design. This process significantly reduces opportunities for defects, weighs less, and costs less. The knowledge gained by this and future launches using the OoA fairing will inform design decisions for ULA's upcoming Vulcan-Centaur rocket, which is expected to debut in early 2022. Other new Vulcan related upgrades that will be flight-proven on this mission include an In-Flight Power System (IFPS) designed to maintain charge in the satellites during the ascent lasting more than seven hours and an enhanced GPS navigation system to provide greater accuracy for the Centaur Upper Stage to place the payloads into highly specific orbits.

Liftoff of an Atlas V rocket from SLC-41 (Photo: ULA)


The 'STP-3' payload is a rideshare, meaning it carries multiple satellites to orbit simultaneously, in this case two. The primary satellite is STPSat-6, which hosts a fleet of different experiments. Among them is the Space and Atmospheric Burst Reporting System 3 (SABRS-3) for the National Nuclear Security Administration which detects potential nuclear explosions as well as space environmental data to compliment nuclear detectors already in place on existing GPS satellites, NASA’s Laser Communication Relay Demonstration (LCRD) experiment which will test technologies in anticipation of future high-speed data relay satellites, and several Department of Defense Space Experiments Review Board space weather and situational awareness instruments.

The secondary payload is the Long Duration Propulsive Evolved Expendable Launch Vehicle (EELV) Secondary Payload Adapter (ESPA), known as 'LDPE-1'. It is designed for a 1-3 year mission life and carries experimental payloads focusing on rapid risk reduction efforts to inform future programs. Both the 'LDPE-1' spacecraft and STPSat-6 are built by Northrop Grumman and will be placed into Geosynchronous orbit.

Launch sequence, graphic courtesy of ULA


The 45th Weather Squadron is predicting a 90% chance of favorable conditions during the launch window. For more information and live webcast visit-

Spaceflight News will be on location for the launch of 'STP-3', follow us on social media for live updates and coverage.



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