Screenshot from ULA Webcast of the launch of USSF-7 or OTV-6. It’s cloudy today. Let’s go anyway
Mission Rundown: ULA - Atlas V 501 - OTV-6 - X-37B
Written: September 7, 2021 - Edit: November 28, 2022
Flying on wings in space
This launch of an Atlas V marks United Launch Alliance’s 139th mission. Atlas V is built and launched by ULA. It will ferry the X-37B orbital test vehicle (OTV-6) with the most payloads it has ever carried into a Low Earth Orbit (LEO). For this mission an Atlas V in a 501 configuration will launch from Space Launch Complex (SLC) -41, Cape Canaveral Air Force Station. The primary customer for this launch is the U.S. Space Force.
Atlas V tail number AV-081, a unique designation assigned to each individual Atlas rocket which began with Atlas-Centaur rockets in the 1960s. The Atlas-Centaur tail numbers (first with the AC-001) were continued by the Atlas I, Atlas II and Atlas III rockets which evolved the Atlas-Centaur design, before being replaced with the “AV” series for Atlas V.
ULA’s Atlas V 501 launched from SLC-41, CCAFS May 17, 2020 at 09:14 EDT
Atlas V 501 with OTV-6 seems to launch in a 44/45 degree orbit from SLC-41 at Cape Canaveral
USSF-7 launched aboard United Launch Alliance’s Atlas V rocket, which flew in the 501 configuration for this launch. This was the eighty-fourth flight of an Atlas V rocket, one of the most proven and reliable rockets currently in service.
Atlas is a two-stage rocket, consisting of a Common Core Booster (CCB) and a Centaur upper stage. It can fly with up to five AJ-60A solid rocket boosters to provide additional performance for heavier payloads or where the rocket is targeting a higher-energy orbit. However, with lightweight payloads like the X-37B Atlas flies without these additional motors. In the 501 configuration there's a 5 meter fairing and a single Centaur engine.
This launch will use the shortest version of the five-meter fairing, which is 5.4 meters (17.7 feet) wide and measures 20.7 meters (68 feet) in length. The composite structure is produced by Swiss manufacturer RUAG, who also makes a similar fairing for the European Ariane 5 rocket.
When Atlas V flies with a five-meter fairing, the fairing attaches to the interstage between the first and second stages, completely enclosing the Centaur upper stage as well as the payload. Because of this, the fairing must be jettisoned during first-stage flight.
By around three minutes, 40 seconds mission elapsed time mark Atlas reached space, and the fairing was no longer needed, so it could be safely discarded. A few seconds later the forward load reactor also separated. This device, which attaches at the forward end of the Centaur, helps to spread some of the payload’s weight across the lower half of the fairing.
Screenshot of Atlas V 501 with X-37B as its payload. It's a tight fit for a space plane. The wings are far too asymmetrical so they will make the rocket veer of course during its atmospheric ascent.
This inclosure of the Centaur 2nd stage makes the fairing far larger than necessary, and also make the fairing look too big. The fairing half is actually made of two ¼ sections, top and bottom bolted together in the middle.
This design feature makes no sense, and increases the fairing mass. Does the Centaur 2nd stage need this fairing design as a reinforcement during assent and MaxQ?
Another reason for this design is the highly volatile Hydrogen gas ability to penetrate any material in fuel tanks, fuelpipes, valves and even the fairings themself.
The payload in the top compartment is pressurized with a dry nitrogen gas, preventing hydrogen gas from penetrating into the payload. With no oxygen there can be no fire or explosion so the payload is secure from this source of destruction.
The sheer number of vent holes in the lower part of the fairings tells me that hydrogen gas is present and abundant enough to cause a major accident. Liquid hydrogen tanks are in their supercooled state even more prone to hydrogen gas penetration and therefore even more dangerous around oxygen and electric spark sources.
The X-37B Payload
This sixth flight of the X-37B is designated United States Space Force 7 (USSF-7) – formerly Air Force Space Command 7 (AFSPC-7) – part of a series of generic designations that are increasingly being used to identify US military space launch missions. As the sixth X-37B mission, the flight is also designated OTV-6.
Now in orbit, the X-37B will acquire another public designation, under the USA series that is used for American military satellites. Each X-37B receives a new USA designation each time it enters space. USA designations have been assigned sequentially since 2006, so USSF-7 is expected to become USA-299 on orbit.
As well as flying on Atlas V, OTV spacecraft can be deployed by SpaceX’s Falcon 9 rocket, a capability that was demonstrated with the OTV-5 launch in 2017.
On its USSF-7 flight, the X-37B is expected to demonstrate new capabilities – including flying with the service module for the first time. This module, which is attached to the aft end of the spacecraft, hosts additional equipment and experiments for the mission.
Photo of X-37B in its fairing. The blue tiles are soundproofing. Can’t you see that it's a padded cell?
Ahead of launch Barbara Barrett, the Secretary of the Air Force, stated that this mission would carry out more experiments than any previous OTV flight. The X-37B spacecraft incorporates a payload bay that can be opened in orbit to expose experiments to space. A solar panel, deployed from the bay, provides power to the spacecraft and its experiments.
During the course of its mission, X-37B will deploy the small FalconSAT-8 satellite for the US Air Force Academy. The latest in a series of experimental satellites built by the Academy for technology demonstration and to give cadets experience constructing and operating spacecraft. FalconSAT-8 carries eight experiments.
Two of these are being carried out on behalf of NASA, investigating the effects of the space environment and radiation on material samples in one experiment, and on seeds in the other.
FalconSAT will also conduct an experiment for the Naval Research Laboratory to investigate wireless power transfer, generating electrical power through the satellite’s solar panels and transmitting it to the ground as microwave radiation.
Deployment of FalconSat-8 happened around or before May 29, when USA-300 appeared on the NORAD list of classified satellites. OTV-6 is designated USA-299.
The planned duration of the X-37B’s mission has not been announced, although the spacecraft has already shown that it is capable of remaining on orbit for over two years.
When it is time for the X-37B to return to Earth it will fire its engine for a deorbit burn, lowering the perigee – or lowest point – of its orbit into the Earth’s atmosphere. Following re-entry into the atmosphere the spacecraft will glide down to a runway landing at one of its three designated landing sites.
It is not clear whether the new service module will remain attached to the X-37B for the duration of its mission, or whether it will be jettisoned partway through. However it’s clear that it is enabling X-37B to change orbit altitude and inclination during the mission, and since the initial orbit allowed it to pass three KH-11 spy satellites.
OTV-6 passed USA-290 at a distance of 29 km--this would allow the KH-11 satellite to perform extremely high resolution sat-squared visual imaging.
Two other passes of KH-11 satellites also occurred that would allow approximately a more "normal" KH-11 resolution: ~10 cm (no atmosphere to muddle actual resolution). OTV-6 passes USA-224 at a distance of 370 km and then USA-245 at a distance of 490 km.
Maybe this is a calibration test of the KH-11 cameras.
