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Atlas 5 launches X-37B spacecraft

Capitalism in space: ULA’s Atlas 5 rocket this morning successfully launched one of the military’s two X-37B reusable mini-shuttles into orbit.

I have embedded the video of the launch below the fold, with the launch occurring at 23:50.

As has been standard procedure during all previous X-37B missions, only a few details about the payloads have been released, though the military has said it wishes to be a bit more open this time.

“This sixth mission is a big step for the X-37B program,” said Randy Walden, director and program executive officer for the Air Force Rapid Capabilities Office. “This will be the first X-37B mission to use a service module to host experiments. The incorporation of a service module on this mission enables us to continue to expand the capabilities of the spacecraft and host more experiments than any of the previous missions.” The service module is attached to the aft end of the X-37B spaceplane, providing additional capacity for experiments and payloads. The X-37B itself, measuring more than 29 feet (8.9 meters) long, also has a cargo bay inside its fuselage.

Secretary of the Air Force Barbara Barrett said Wednesday that the Air Force’s Rapid Capabilities Office is partnering with the U.S. Space force and the Air Force Research Laboratory on the next X-37B mission. … “This important mission will host more experiments than any prior X-37B flight, including two NASA experiments,” Barrett said Wednesday. “One is a sample plate evaluating the reaction of select significant materials to the conditions in space. The second studies the effect of ambient space radiation on seeds.”

The X-37B also carries a space-based solar power experiment. “A third experiment designed by the Naval Research Laboratory transforms solar power into radio frequency microwave energy, then studies transmitting that energy to Earth,” Barrett said.

Once in orbit, the X-37B will also release a small satellite named FalconSat 8. Developed by Air Force Academy cadets in partnership with the Air Force Research Laboratory, the small satellite carries five experimental payloads. It will be operated by by the Air Force Academy’s Cadet Space Operations Squadron

They have not said how long this X-37B will remain in orbit.

The leaders in the 2020 launch race:

8 China
6 SpaceX
6 Russia
6 Europe (Arianespace)

The U.S. now leads China 11 to 8 in the national rankings, and will likely increase that lead very early tomorrow in the next day or so when SpaceX completes its next scheduled Falcon 9 Starlink launch. (Because of weather they have pushed back one day.

Conscious Choice cover

Now available in hardback and paperback as well as ebook!


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Conscious Choice: The origins of slavery in America and why it matters today and for our future in outer space, is a riveting page-turning story that documents how slavery slowly became pervasive in the southern British colonies of North America, colonies founded by a people and culture that not only did not allow slavery but in every way were hostile to the practice.  
Conscious Choice does more however. In telling the tragic history of the Virginia colony and the rise of slavery there, Zimmerman lays out the proper path for creating healthy societies in places like the Moon and Mars.


“Zimmerman’s ground-breaking history provides every future generation the basic framework for establishing new societies on other worlds. We would be wise to heed what he says.” —Robert Zubrin, founder of founder of the Mars Society.


All editions available at Amazon, Barnes & Noble, and all book vendors. The ebook can be purchased direct from my ebook publisher, ebookit, in which case you don't support the big tech companies and I get a bigger cut much sooner. Note that the price for the ebook, $3.99, goes up to $5.99 on September 1, 2022.


Autographed printed copies are also available at discount directly from me (hardback $24.95; paperback $14.95). Just email me at zimmerman @ nasw dot org.


  • Rose

    Tory is rockin’ quite the stache:;topic=47236.0;attach=1911670;image

    Good for him. I think it adds a lot of character.

    Bob, you mentioned Twitter viewing trouble. Earlier I had posted a link to these shots of the X-37B encapsulation, showing off Atlas V’s new, blue, cheaper and better, sound absorbing foam:

    Does it help to directly link the individual photos?

    Compare to photos from earlier missions to see how they avoid showing off the new service module.

    Regarding the Starlink launch date:
    “Due to a tropical depression developing off the Southeast Coast of the U.S., now targeting Tuesday, May 19 at 3:10 a.m. EDT for the Starlink mission—SpaceX teams will continue monitoring launch and landing weather conditions”

  • Rose: Yes, linking directly to the images works. Twitter is garbage, in more ways than one.

  • LocalFluff

    Wow, “a space-based solar power experiment”! That’s the first of its kind that I have heard of. I think that concept will have applications, but to beam the power to assets in space (such as on the night side of the Moon, so that a Yututwo rover there never would need to sleep) rather than down to Earth.

  • Ray Van Dune

    Watched the launch this morning on Everyday Astronaut’s feed, which I think needs improvement. Tim usually has thoughtful stuff to say on his own webcasts but I found him irritating here. He seemed to be clobbering the ULA launch control, which admittedly talks a lot, while Spacex stays quiet.

    What grabbed me was the slooow liftoff! I thought it was failing for a second there! Have not seen anything that slow since a Saturn 5. The ULA host showed clips of the other four X-37B missions they have done, and all were the 501 config (0 strap-ons) except one, which had at least 3! Strange. I wonder if that slow initial acceleration makes the limits for ground wind speeds lower? It must. That umbilical tower ULA usees doesn’t flop out of the way like Spacex’s.

  • Captain Emeritus

    Watched the launch live this morning and actually gasped (or choked on my coffee, not sure which) during the staging event.
    At the RL-10 startup, the exhaust (or vent tube) next to the engine bell, abruptly cut off it’s stream after starting up for a couple seconds.
    I thought the motor had failed to crank. However, there appeared to be some acceleration away the Russian powered, expendable “Atlas”.
    The live stream also terminated at that instant.
    Checking other vids, of the same event, in the same configuration, shows the Tube in question, continues to exhaust overboard while the RL-10 is operating.
    Anybody else notice that?
    Can you tell me the function of the exhaust tube?
    Obviously, the X-37B can re-enter ok. Think it could deadstick in from a failure to achieve orbit scenario?
    I saw another launch once, where the vehicle failed, (you could see it diverge from the nominal track)
    but, the commentator droned on and on while they put up the animation, telling how great it was going.
    Did the X-37B make it to orbit.?
    Would they tell us?

  • Captain Emeritus: For the function of the exhaust tube, see this video:

    Comparing today’s modern rocket engines

    I need to watch it again to remember what its for, but until I watched it I hadn’t realized that the Merlin engine has one too.

  • Andrew_W

    The RL-10 is an Expander rocket cycle. Expander rocket engine (closed cycle). Heat from the nozzle and combustion chamber powers the fuel and oxidizer

    For that to work I expect there has to be some separate combustion process (a small solid rocket motor?) powering the turbo pumps until there’s enough heat from the nozzle and combustion chamber to power them, if so only the initial & temporary exhaust from that SRM would be expelled from vent tube.

  • Andrew_W

    The RL-10 engine starts by using the pressure difference between the fuel tank and the nozzle exit (upper atmospheric
    pressure), and the ambient heat stored in the metal of the cooling jacket walls. The engine “bootstraps” to full-thrust within
    two seconds after ignition.
    A typical plot of the valve movement during engine start is
    shown in Figure 2. To initiate start, the FSOV is opened and
    the fuel-pump discharge cool-down valve (FCV-2) is closed.
    The interstage cool-down valve (FCV-1) remains partially
    open in order to avoid stalling of the fuel pump during engine
    acceleration. The pressure drop between the fuel inlet and the
    combustion chamber drives fuel through the cooling jacket,
    Figure 1: RL-10A-3-3A engine diagram
    picking up heat from the warm metal. This pressure difference also drives the heated fluid through the turbine, starting
    rotation of the pumps, which drive more propellant into the
    system. At start, the OCV also closes partially, restricting the
    flow of oxygen into the combustion chamber. This is done to
    limit chamber pressure and ensure a forward pressure difference across the fuel turbine after ignition of the thrust chamber.
    Figure 2: RL-10A-3-3A Valve schedule for Start-up Simulation [3]
    Ignition of the main combustion chamber usually occurs
    approximately 0.3 seconds after the main-engine start signal
    (t = 0) is given (for first-burns). The ignition source is a torch
    igniter powered by an electric spark. The ignited combustion
    chamber provides more thermal energy to drive the turbine.
    As the turbopumps accelerate, engine pneumatic pressure is
    used to close the interstage cool-down valve completely and
    open the OCV at pre-set fuel and LOX pump discharge pressures. The OCV typically opens very quickly and the resultant flood of oxygen into the combustion chamber causes a
    sharp increase in system pressures. During this period of fast
    pressure rise, the thrust control valve (TCV) is opened, regulated by a pneumatic lead-lag circuit to control thrust overshoot. The engine then settles to its normal steady-state operating point.

  • Captain Emeritus

    A great reply!
    Reminded me of the first day in 727 electrical class.
    Instructor walks in, places a dot on the blackboard and says “this is an electron, this is where we begin!”
    Most of us just wanted to learn how to operate it, not build it ;-).
    I will study the pdf closely. Thanks for sharing.
    Is it true the Russians light their booster motors, with a 4 foot long mahogany match, dipped in a pyrogen, electrically actuated, and installed by inserting into the nozzle
    and secured into the throat of the combustion chamber?
    Thanks for the video link Mr. Zimmerman.

  • Rose

    @Ray Van Dune The ULA host showed clips of the other four X-37B missions they have done, and all were the 501 config (0 strap-ons) except one, which had at least 3! Strange.

    Good catch, Ray! That was an editing error on ULA’s part. Here is a link to today’s webcast to where they show a clip from what they are calling the OTV-4 X-37B mission.
    “May 17 Live Broadcast: Atlas V USSF-7”

    But that Atlas V 551 isn’t OTV-4; it is actually footage from AFSPC-11 with the military comsat CBAS (Continuous Broadcast Augmenting SATCOM) along with some ride shares including inspector sat Mycroft, launched on April 14, 2018, 19:13 EDT. Here is its webcast, linked to ignition.
    “Atlas V AFSPC-11 Live Launch Broadcast (April 14)”

    Exact match, from the lighting, to the waves, to the condition of the MLP, to the behavior of flame, water, and umbilicals. (Thought the footage from today’s webcast does cut to a different camera sooner.)

    Here is the actual launch of the OTV-4 X-37B on an Atlas V 501.
    “Atlas V – AFSPC-5 (X-37B OTV-4 + CubeSats) Launch – May 20, 2015”

  • Ray Van Dune

    The RD-180 is a “closed-cycle” engine, as is the SpaceX Raptor, meaning they while they do use a small portion of their fuel and oxidizer to spin the turbopumps that feed the main engine, they DO NOT then exhaust the results of that combustion overboard in a way that does not product thrust.

    Instead they capture the unburnt portion and feed it back into the main combustion chamber to produce additional thrust. “Closed-cycle” thus means nothing is wasted – nothing is dumped that could produce additional thrust.

    The Merlin and the RL-10 are “open-cycle” engines, in that once the propellants used to spin the pumps are burned, they are vented to space along with the residual energy they have that could produce thrust. This avoids the complexity of re-introducing them into the main thrust chamber. at the cost of slightly less efficiency. That’s it in a nutshell.

  • Willi

    What happened with the Starlink 7 launch? It was supposed to take place early Sunday morning.

  • Andrew_W

    Ray Van Dune: “The Merlin and the RL-10 are “open-cycle” engines,. . .”

    Are you sure about that? Everything I’m finding says the RL-!0 uses a closed expander cycle, not a bleed expander cycle, though it does have opened bleed valves during start-up.

  • Willi: Read this article. It has slipped to Tuesday due to weather.

  • Ray Van Dune

    Andrew, you are probably right… I assumed if it had bleed valves it was open cycle.

  • Edward

    Captain Emeritus was concerned: “The live stream also terminated at that instant.

    The beginning of the broadcast tells us that the customer requested that the stream end at second stage ignition.

  • Rose

    SpaceX’s next Falcon 9 / Starlink launch has been postponed until after the DM-2 mission, presumably because there wasn’t enough time to guarantee a turnaround of their ASDS landing barge OCISLY. (The other East Coast barge, JRTI, is still being refitted.)

    Michael Baylor: “SpaceX’s next launch will have crew onboard. The Starlink launch is in fact now postponed until after Demo-2 due to not enough time to turnaround OCISLY.

    JRTI still has several weeks of trials ahead of it before it will be ready.”

    Gavin –
    “GO Quest is leaving Cape Fear and has set a destination of Cape Canaveral with an ETA of Tuesday 19th.

    The Starlink launch might be canceled. Rough seas are forecasted for the 19th and they cannot delay further without conflicting with DM-2 recovery.

    Wait for SpaceX to confirm.”

    @Ray Van Dune — Look above for a response to your Atlas V 551 observation which got lost behind newer posts while awaiting moderation.

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