X-37B OTV-6 | Atlas V 501

What’s all this mean?

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.

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(Subject to change)
May 17, 2020 – 13:14 UTC – 15:43 UTC | 09:14 – 11:43 EDT
Mission Name and what it is
USSF-7 / OTV-6
Launch Provider
(What rocket company is launching it?)
United Launch Alliance (ULA)
Primary Customer: US Space Force
Secondary Customer: NASA, US Air Force, US Navy
Atlas V 501
Launch Location

Space Launch Complex (SLC) -41, Cape Canaveral AFS, Florida, USA

Payload mass
Classified, up to 8,123 kg
Where are the satellites going?
Low Earth Orbit (LEO)
Will they be attempting to recover the first stage?
No, this is not a capability of United Launch Alliance 
Where will the first stage land?
It will crash into the Atlantic ocean
Will they be attempting to recover the fairings?
No this is not a capability of United Launch Alliance 
Are these fairings new?
This will be the:
  • 84th flight for an Atlas V rocket
  • Sixth flight of the X-37B (OTV-6)
Where to watch
Livestream link for ULA’s stream.
Graphic by Geoff Barrett Rocket by Stanley Creative

The Atlas V Rocket

The Atlas V Common Cores are manufactured near Decatur, Alabama and then transported via the Mississippi river and the Gulf of Mexico to either California or Florida aboard the R/S Rocket Ship.

What does 501 Mean?

The configuration of the Atlas V for the USSF-7 mission  is 501. The last three numbers or letters in the Atlas V’s name denote the configuration of the rocket. First, the number or letter shows the fairing diameter size (in meters) or ‘N’ for no fairing. In this case the number 5 obviously stands for 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 none strapped onto the center core.

The third and final number refers to the number of engines on the Centaur Upper Stage, which can be either one or two. In this case there will be one Aerojet Rocketdyne RL-10C engine. The only time that there have been two engines (while on an Atlas V) was on Starliner’s OFT-1 (as of the date of this article).

So to review, for the USSF-7 mission, this rocket has a five-meter fairing, zero solid rocket boosters, and one RL-10C engine on the Centaur Upper Stage.

X-37B and its payloads

Since this is a launch for the US Space Force, not many details are available for the public. Most of the payloads inside of the X-37B are classified. Therefore we do not have detailed information about the payload, or in what orbit the OTV will end up. One thing that we do know is that it will be in LEO. Besides the US Space Force as the primary customer, NASA and the US Air Force will also have payloads on board of this particular X-37B.

This flight will mark the first time that a service module will serve as a bay for experiments and payloads. Therefore it will carry more payloads than it has ever before.

X-37B OTV-6 inside fairing
The X-37B for OTV-6 during its placement in the fairing. (Credit: US Space Force)

The known payloads

NASA will have two experiments on board of the X-37B’s service module. They will study the results of long exposure to radiation, and other effects due to exposure to vacuum in space, on seeds and “selected significant materials” presented on a so-called “sample plate”.

The main US Air Force payload is a micro-satellite called FalconSAT 8,  which in turn carries five experimental payloads. The satellite was developed by the Air Force Academy in partnership with the Air Force Research Laboratory. After deployment from the X37B, it will be operated by cadets at the Academy.

The US Naval Research Laboratory also has a payload onboard. This is an experiment that will transform solar power into radio frequency microwave energy which could then be transmitted to the ground.

X-37B – An Unmanned Miniature Space Shuttle

The X-37B, also known as Orbital Test Vehicle (OTV) is a reusable unmanned spaceplane with similar aerodynamic properties to the Space Shuttle. Currently, the U.S. Space Force operates the unmanned spaceplane to showcase reusable space technologies during orbital missions. NASA originally contracted Boeing with the development of the X-37A following its predecessor the X-40.


Originally, the X-37B spaceplane began in 1999 as X-37A, a NASA project which would be developed for the agency by Boeing. Over a five year span Boeing was awarded nearly $500 million to develop the X-37A. In September of 2004 the project was transferred from NASA over to DARPA where it became classified. It took DARPA nearly two more years before the X-37A made its first free glide flight. Upon landing, it overshot the runway and suffered minor damage.

Following a few more free glide tests, the US Air Force announced the Orbital Test Vehicle (OTV) program, now designated X-37B. Again, Boeing was the primary contractor to build the spaceplane. At first it was designed to be on orbit for up to 270 days and launched inside the payload bay of a Space Shuttle. Due to the 2003 Columbia disaster, it was redesigned to launch on top of a Delta II, although this never happened either.

Concept of X-37B inside Shuttle's bay
A concept illustration of an X-37B inside a Shuttle’s payload bay. (Credit: NASA)

Orbital Test Vehicle Program (OTV)

On April 22, 2010 OTV-1 launched on board of ULA’s Atlas V 501 and stayed in orbit for 224 days. Up until today, the two X-37B vehicles have completed five orbital missions and have spent a total 2,865 days combined in orbit. The longest mission was OTV-5, which stayed in orbit for over two years, 779 days 17 hours and 51 minutes to be exact. OTV-1 to OTV-4 were launched on an Atlas V 501, whereas OTV-5 was launched on SpaceX’ Falcon 9. Due to the program being classified, there is virtually no information on the specific missions. We don’t even know which of the two X-37Bs went into space on the respective missions.


In 2011, Boeing announced plans for the X-37C – a scaled up version of the X-37B that would be able to hold up to six astronauts inside its pressurized cargo bay. Both the X-37B and the X-37C would be launched on an Atlas V. However, the X-37C variant would have launched directly on top of the rocket, whereas the X-37B is encapsulated by fairings. The X-37C could have been a potential commercial internal competitor to the CST-100 Starliner for the Commercial Crew Program, but in the end lost out to the more traditional capsule design of the CST-100.

Size comparison of different X-37 variants, X-37B, X-37C and Space Shuttle
Size comparison between the X-37B, the X-37C and the Space Shuttle and how they could have been launched. (Credit: Boeing)
  1. I saw a bright light moving from west to east about two hours after the launch over germany, it seemed too bright and fast for a plane and way too bright for an ordinary sattelite. I didn’t find any information about the orbit of otv-6, is it plausible that I saw the vehicle passing by?

    1. Zwei Stunden nach dem Launch war es noch sehr hell, glaube daher nicht, dass es wirklich das X-37B war welches vorbeiflog.

      It was still very bright two hours after launch, therefore I don’t think that it was the X-37B you saw passing by.

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