Screenshot from ULA Webcast of the launch of STP-3. Duck you sucker. The ‘Soup’ is flying today
Mission Rundown: ULA - Atlas V 551 - STP-3
Written: November 25, 2022
Testing the Alphabet Soup
ULA (United Launch Alliance) launched its 90th flight with an Atlas V 551 rocket and its fifth and final mission of 2021. Launching from SLC-41 (Space Launch Complex 41) in Cape Canaveral, Florida, the STP-3 mission is lofting two experimental satellites for the United States Space Force.
The mission will also test several new technologies onboard the company’s Atlas V launch vehicle during the longest duration mission for an Atlas rocket to date. Liftoff occurred on December 7 at 05:19 EST (10:19 UTC) after several holds for high altitude winds.
The attachment of five side-mounted solid rocket boosters (SRBs) to the Atlas first stage will generate three-quarters of the energy necessary at liftoff to power the vehicle on to a complex, seven-hour flight. The core Atlas V booster will do the remaining 25%.
NOTAM hazard areas where Atlas V 551 will drop off SRB boosters, fairings and 1st stage
The number 5 obviously means a 5 meter fairing. The second number determines the number of strap on solid rocket boosters (SRBs). It can range from 0 to 5, and in this case, there are five on various sides of the center common core.
The third and final number refers to the number of engine bells on the Centaur Upper Stage, which can be either one or two. In this case there will be one engine. The only time that there have been two engines (while on an Atlas V) was on Starliner’s OFT-1. So to review, for the STP-3 mission, this rocket has a five-meter fairing, five solid rocket boosters, and one engine on the Centaur Upper Stage.
It’s unique to the Atlas rocket to have their solid rocket boosters (SRBs) positioned in this way. When, like in this case, 5 SRBs are used, they are positioned with two on one side and three directly opposite of them. If you notice carefully in the image of Atlas core boosters, there are long and somewhat flat pipes “running” down the side of the first core stage.
These are raceways and carry fuel from the tanks down to the engines and some carry gasses back up to the tanks to pressurize them so the fuel stays flowing out the pipes.
When Atlas was designed, these two raceways were placed in their positions without the thought of SRB placement. So when more SRBs were needed, they were placed in the most convenient spot. Two SRB between the raceways and three opposite them.
The offset of the thrust won’t make it fly in the wrong direction. The engines on the core stage can gimbal, they counteract that offset of thrust by vectoring their thrust which is known as Thrust Vector Control, or TVC. The SRBs, and most of them for that matter, do not have TVC abilities, but their nozzles can be angled and turned slightly sideways. That will counteract some of that offset SRB thrust.
During the STP-3 mission, ULA plans to demonstrate three new technologies onboard its Atlas V rocket: a new fairing design, an upgraded power system for the two spacecraft, and what the company calls “Enhanced Navigation.” All of these technologies will feature on the company’s future Vulcan Centaur rocket.
Manufactured in Decatur, Alabama–right next door to ULA’s factory–by RUAG Space, the new fairing uses a manufacturing method called Out-of-Autoclave, and will replace the fairings made by RUAG in Switzerland. While they are the same size as previous Atlas V 5.4 meter-class fairings, the new process “weighs and costs less while being easier and quicker to make,” according to ULA.
Due to STP-3’s nearly seven hour journey to a circular geosynchronous orbit, the Atlas V rocket is flying for the first time with what the company calls an IFPS (In-Flight Power System) which keeps the batteries of both spacecraft fully charged throughout the flight. This means that the spacecraft have more time on battery power before needing to rely on their deployable solar panels after separation from the Atlas V’s Centaur upper stage.
ULA is also debuting what the company refers to as “Enhanced Navigation,” a system that uses GPS data to compliment the rocket’s onboard flight computer in order to increase orbital insertion accuracy. According to ULA, the system was tested on a previous launch last year, and “will be available for use on all Atlas V missions going forward.”
The ULA-manufactured upper stage for Boeing’s Space Launch System, called ICPS, will also use “Enhanced Navigation.” ICPS is short for Inner Cryogenic Propulsion System and is a modified Centaur second stage loaded with liquid Hydrogen and Oxygen.
The STP-3 Payload
STP-3 marks the third dedicated launch for the U.S. Space Force’s Space Test Program. The program is designed to fly experimental payloads in order to mature technologies for future Department of Defense missions. The STP-3 mission is composed of two payloads: a primary spacecraft and a rideshare spacecraft.
The primary spacecraft is known as STPSat-6, and was designed and built by Northrop Grumman. STPSat-6 will host nine experiments including those for NASA and the NNSA (National Nuclear Security Administration).
The NNSA’s main experiment, called the SABRS-3 (Space and Atmospheric Burst Reporting System 3), is designed to detect nuclear detonations on Earth. SABRS will complement Global Burst Detector payloads on GPS satellites as well as the SBIRS (Space-Based Infrared System) constellation.
NASA’s LCRD (Laser Communications Relay Demonstration) is designed to test laser communications as an alternative to typical radio communications for NASA spacecraft. LCRD will communicate with ground stations as well as future in-space experiments such as a payload called ILLUMA-T that will be attached to the ISS in 2022.
Other payloads aboard STPSat-6 include “several of DoD Space Experiments Review Board space weather and situational awareness payloads,” according to ULA.
The rideshare spacecraft, LDPE-1, which stands for Long Duration Propulsive ESPA number 1 — E in ESPA meaning EELV (Evolved Expendable Launch Vehicle) a secondary payload adapter. E in EELV stands for ESPA is a EELV Standardized Spacecraft Adapter size originally designed for use on the Atlas V and Delta IV launch vehicles, and it is now also used on Falcon 9. - Did anyone get those letters? - I still don’t get it.
ESPA is a EELV Standardized Spacecraft Adapter
EELV is a Evolved Expendable Launch Vehicle
LDPE-1 is a Long Duration Propulsive ESPA
Sir. Can I have another bowl of ‘Alphabet’ Soup? :Oliver Twist
LDPE-1 was also built by Northrop Grumman, and it is based off of the ESPAStar line of spacecraft the company produces. It also derives technologies from another ESPAStar named EAGLE that was flown on a previous Atlas V 551 mission in 2018.
While LDPE-1 will carry several payloads, the exact nature of them are currently unknown. At least two more LDPE spacecraft are scheduled to launch on Space Force missions, including a Falcon Heavy launch called USSF-67.
Both STP-3 payloads will be delivered directly into a geosynchronous orbit approximately 36,100 kilometers above the Earth.
This is a six port ESPA ring under construction being fitted with 3U CubeSat dispensers. Source
The Atlas V 551 rocket
The Atlas V core in use for this mission is AV-093. Atlas V 551 stacking will begin working in the coming days, five GEM 63 solid rocket boosters and the Centaur upper stage with its RL10C-1 engine will be hoisted into place. STP-3 payload attachment occurs later in November before rollout to Space Launch Complex-41.
Inside the Vertical Integration Facility - VIF, a team of engineers fastened the payload fairing, which houses the U.S. Department of Defense’s (DoD) Space Test Program Satellite-6 (STPSat-6) spacecraft. LCRD is hosted on STPSat-6. The mission is scheduled to launch on Dec. 5 from Launch Complex 41 on CCSFS, with a two-hour launch window beginning at 4:04 a.m. EST.
The fully stacked rocket and payload stands 196 feet tall and is anticipated to roll out on a mobile launch platform from the VIF to the launch pad on Dec. 3. The rocket’s Centaur second stage and spacecraft will remain attached until 4 minutes, 33 seconds after launch, with deployment of STPSat-6 scheduled about 6 hours, 30 minutes after launch.
On December 6, the Atlas V 551 was rolled from its Vertical Integration Facility to its launch pad at Space Launch Complex 41. Afterward, the rocket’s first stage was filled with its kerosene fuel, which can be loaded ahead of time as Atlas V does not yet rely on the use of super-chilled kerosene, such as Falcon 9.
Seconds before launch, the RD-180 engine on the first stage ignited. At T-0 seconds, the five GEM-63 solid rocket boosters ignited, followed by liftoff at T+1.1 seconds.
About 35 seconds after launch, the Atlas V passed the speed of sound, or Mach 1.
At one minute and 47 seconds after launch, all five solid rocket boosters were jettisoned. First, two separated, followed by the other three about two seconds later. The payload fairing separated from the rocket about three and a half minutes after launch.
At four minutes and 27 seconds after launch, the RD-180 engine on Atlas’ first stage shut down, and the Centaur upper stage carrying the STP-3 payloads separated. Centaur’s RL-10 engine burned for about six minutes to reach an initial orbit.
An hour and seven minutes after launch, Centaur ignited once more and burned for about six minutes to raise the apogee, or highest point in the orbit, to a geostationary altitude.
After a roughly five hour long coast phase, the Centaur ignited again, circularizing its orbit and changing its orbital inclination from about 26 degrees to zero degrees with a roughly three minute burn.
At six hours and 30 minutes after launch, STP Sat-6 separated, followed by LDPE-1 at seven hours and 10 minutes, ending the longest duration mission in Atlas rocket history.
The upper stage Centaur’s RL-10 engine depleted its last reserves of propellant to lift itself into a graveyard orbit some 38 655 km away from earth. The remaining gasses and fuel vapors will be vented at apogee in order to raise the perigee just a little.
The Centaur’s propellant tanks must be empty to avoid exploding like a rotting toad in the sunlight. At least three upper stage Centaur’s weren't purged and exploded in 10-15 large pieces of space debris.
