Geoff FordenX37B Orbit Found, Mystery Remains

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You gotta’ love amateur satellite observers. They spend hours glued to their telescopes, binoculars, and/or video cameras for the shear joy of seeing a man made object cross the sky. Their latest triumph is determining the orbit of the X-37B Orbital Test Vehicle (OTV-1). Through careful planning and diligent observations, these observers have spotted the X-37B and determined its orbit. They will continue to observe it and, as a final check on their hypothesis, determine its mass to surface area ratio; a final step in assuring themselves that it is a payload as opposed to a rocket body.

The OTV-1 has an orbital inclination of 40 degrees and an altitude of about 400 km. It is instructive to look at other satellites belonging to the US with similar inclinations and altitudes since they might give an indication of the type of sensors the OTV could deploy. These have included the TACSAT-1, -2, and -3 satellites, where TACSAT stands for Tactical Satellite. All three are said to be intended for feeding data directly to the battlefield commander and for allowing for him to determine their tasking as well.

The requirements for TACSAT-3, which has a hyperspectral imager (other TACSATs have different sensors), have a concept of operations where the timeline from when battlefield commander tasks a satellite as it passes over head to receiving “decision quality” images is less than 30 minutes. And eventually less than 10 minutes. But what good does a 10 minute timeline do when it can only occur every four days—the revisit time of either a TACSAT or a OTV?

One possibility is that the OTV may be chock full of TACSATs and could use its orbital maneuverability to lay down ten or twenty of the little guys. The OTV could space them out so that they were passing over the theater of operations every two to four hours and only during daylight as an added benefit. But even that probably does not justify an expensive space plane. After all, you could have an expendable bus deploy the satellites at different points along the orbital plane. One possibility is related to the fact that the TACSATs eventually “precess” into night. Perhaps the space plane comes by, picks them up with a robot arm much like Canada supplied the space shuttle, and repositions them so they pass over the theater in daylight. I’m not sure if that’s the most economical way of doing it, but it might be. And if it is, the robot arm might make it worth recovering the “bus,” i.e. using a space plane.

UPDATE: Just to be clear, the mystery is how a space plane can be used in any realistic way for battlefield intelligence.


  1. Azr@el (History)

    “..the OTV may be chock full of TACSATs and could use its orbital maneuverability to lay down ten or twenty of the little guys.”

    The first tacsat massed 100kg and was found to be almost completely worthless. The Tacsat 2 & 3 massed 370 and 400 kg respectively, i.e. the same range as the Israeli recce sat. The payload of the x-37b is in the ballpark of 230kg, which pretty much rules out the ‘x-37b as tacsat carrier’ theory.

    x-37b is meant for rapid recce. i.e. a new threat is detected, or a preexisting area flares up and US theater commanders or Washington wants to bump up the density of eyes in skies in that band; x-37b to the rescue. x-37b is right now being tested out to provide optical intel for Iraq and Afghanistan, it’s carrying a hyperspectral imaging device made by an L.A. based outfit, nothing fancy.

    Let’s not overdo the accelerator on the imagination thing for space lest we wind up with global strike and photon torpedoes on the mind.

  2. anonymous (History)

    Why use a re-usable vehicle to launch TACSATs? Its a waste of lifting power to carry the winged spacecraft in addition to the payload, as there is no need to bring the TACSATs back. Put the TACSATs on a bus from a conventional launcher — its more efficient.

  3. Geoff Forden (History)

    Why do I always get the impression that nobody actually reads what I write?

  4. FSB

    Like the original shuttle there is no one reason for this vehicle that really makes sense. The decision by committee as the committee moved from NASA to DARPA to AF thought it may be cool to have such a shuttle.

    What was the purpose of the space shuttle or the ISS or missile defense for that matter? To satisfy the technically ignorant wishes of the powers-that-be.

    Smart people looking for answers will be disappointed.

  5. John Schilling (History)

    If X-37 is meant for “rapid recce”, there’s a bit of a problem in that the X-37 can only reach orbit (or anything close to orbit) on top of an EELV, and EELV launches need to be scheduled roughly two years in advance.

    If the idea is that an X-37 already in orbit will perform “rapid recce”, the problem is that an X-37 in orbit will pass over a particular target very predictably once every twelve hours. It might, by consuming the bulk of its on-board propellant, be able to arrange one pass as much as an hour and a half ahead of schedule.

    And no, the Air Force doesn’t have any other launchers in development that might A: carry an X-37 and B: provide a response time of less than months.

    As for using a re-usable launch vehicle to launch Tacsats, the X-37 is not a reusable launch vehicle. It is not a launch vehicle of any sort. It is a payload.

    One whose actual utility is, as Geoff notes, somewhat of a mystery.

  6. Mike (History)

    @Geoff: Since this is an academic website full of academics, you’re pretty much bound to get people inserting their own opinions based on the title of your article – that’s just the way the world works.

    As for the question, this quote, “..the OTV may be chock full of TACSATs and could use its orbital maneuverability to lay down ten or twenty of the little guys.”, which Ar@zel dismisses, is probably closer to the reality. Anyone who works in US Military Space knows that the decided future of US Space is Operationally Responsive space – the key to which is placing useful, short time-line assets in place in a matter of hours to provide battlefield reconnaissance and intel. While a 10-minute hyperspectral image is something of a pipe-dream at the moment, being able to put a constellation of very small satellites over a world hotspot on the period of hours is not. This is much more easily done by a spacecraft holding them (especially if the craft will eventually not need a separate booster rocket) than by putting them on top of a rocket. Also, the plane could carry enough delta-v to reliably insert all members of a constellation into different orbital slots for constant point surveillance over a period of time.

    Your idea of the Canada Arm is a good one, but I feel is still much too complex for any near future platform. I just think the entire key to the X37B is timeliness of response – if say, a northern country attacks a southern one, can we put a surveillance asset overhead within 12-24 hours without killing the delta-v budget of an on-orbit asset?

  7. Izuki Nomura (History)

    What was the purpose of the original X20 (Dynasoar) also build by Boeing?

  8. John Schilling (History)

    If, say, a northern country attacks a southern country, every surveillance asset we already have on orbit will pass overhead within 12 hours, and again every 12 hours after that, without any fuss. If that isn’t enough, we can put more surveillance assets on orbit, but:

    A: that will take weeks or months, not days,

    B: each new asset will merely add one more regularly-scheudled pass every twelve hours,

    C: neither X-37 nor any plausible X-37 follow-on will change any of this.

    The X-37 simply does not work as a new and improved spacegoing SR-71, no matter how many people might want it to or believe it to.

  9. Azr@el (History)

    Let’s clarify a few points:

    A) The goal of the Air Force, for at least my lifespan, has been to gain responsive access to space. This will not change, and they will develop and deploy technologies to take advantage of rapid access to space, even before that goal is realized.

    B) Hyperspectral imagery involves continually calibrating a wide response sensor. It doesn’t take pictures, it takes tracks and creates 3D models of terrain while an onboard library built into it’s firmware highlights objects by their spectral signature. This happens in real time, whether it is a module on a UAV or a recce sat.

    C) The dynasoar was originally conceived as a manned bomber but the icbm made it obsolete before it could gain institutional momentum. Then like all strike platforms that can no longer achieve their original mission it was delegated to recce, but before that could happen recce satellites became sufficiently automated to kill it all together. The X-37b follows pretty much the same arc, originally conceived of as a global strike vehicle; it was meant to advantage of increased plane changes theoretically available to a hypersonic glider at low delta-vee penalty. Unfortunately like all the vast majority of things that look good on paper; hypersonic skipping in the upper atmosphere to shift planes didn’t pan out for a variety of reasons, thus the x-37b was relegated to a recce role to preserve the careers of the men pushing the program.

  10. Mike Goldstein (History)

    Maybe the darn thing has a chemical laser on board. Death from above etc. Reusable because it needs recharge. Just putting it out there.

  11. anonymous

    Under the assumption that an expendable bus would be a cheaper alternative, the combination of arm and payload bay on a recoverable vehicle suggests the possibility of returning objects from orbit.

  12. 3.1415 (History)

    Being totally ignorant on these toys, I noticed that this gadget is not designed to survey high latitude parts of earth, i.e. not for the Russians nor even the Chinese, but for people or things in the warmer part of earth, where the poor economics in general tends to drive hostile feelings toward the Empire.

  13. Anony-mouse

    “…where the poor economics in general tends to drive hostile feelings toward the Empire.”

    or where the empire’s heavy-handed intervention causes bad feelings

  14. Robin Stowell (History)

    Perhaps it could retrieve dead satellites, American or otherwise, and collect some of the space junk that will jeopadise the safety of future space travel.

  15. Stewart (History)

    Looks just like an expensive version of Virgins Spaceship One to me… Even the carrier looks like it was made by Rutan himself. A more sensible way to get up the than strapping yourself to a bomb…

    Just a thought.

  16. Psngray

    Satellites have a finite amount of fuel and are not designed to land. The x37 is designed to land. There are so many uses for this vehicle it’s hard to list them all. Every thing from refuel and repair missions to ultimate satellite killer. At the very least it’s a economical tools for maintaining the air force presence in space.

  17. Brent

    Just a thought but what is the possibility that the X37B could move around out there and establish geosyncrinous (sp) orbit over a hot spot and provide real-time information of what is happening on a battlefield and then, when the battle is over, move on to another hot spot? I mean, if I was going to design a ‘space-based SR71’ I would want it to have that capability.