Traveller Tech: X-37B

X-37B On Orbit (NASA)


The X-37B Orbital Test Vehicle, or OTV, is designed to be a reliable, reusable, unmanned space platform for a TL8 Aerospace Force. The OTV is designed for vertical launch to low earth orbit (LEO) altitudes where it can perform long duration missions. Upon command from the ground, the OTV autonomously re-enters the atmosphere, descends and lands horizontally on a runway. While it does have some capability for orbital inspection, repair, and retrieval, it is limited by its payload bay and altitude range. There are some who claim the OTV is actually an orbital weapons system for attacking targets on the ground. (Design Note: Although one could theoretically build a spaceplane at Tech Level 7, the choice to make this a TL8 platform is driven by the advanced remote control and solar cells.)

The following employment concepts draw heavily on the X-37B Fact Sheet available from the Secure World Foundation (see sources).

Concept – X-37B as an on-orbit sensor platform and test bed

  • X-37B payload bay can carry various sensors used for intelligence collection from space, potentially including radar, optical, infrared, and signals/electronic intelligence (SIGINT/ELINT) suites


  • Ability to flight test and return experimental sensors and satellite hardware would be of significant benefit to military
  • Ability to re-configure the payload bay contents for various sensor packages makes it much more flexible than having to procure multiple satellites
  • X-37B is more maneuverable once in orbit than many satellites, allowing for more flexible ground coverage


  • Prompt response is questionable given that it is tied to a launch vehicle and associated processing timelines and launch pad availability requirements

Concept – X-37B as a deployment platform for satellites

  • X-37B can be launched into orbit and deploy multiple small satellites on a very timely basis to support time sensitive warfighter needs


  • Flexibility in payload configuration, you don’t need to integrate each new satellite to the booster (the satellites get integrated to the X-37B, which then gets integrated to the booster)
  • Deployment could be done in a semi-stealthy manner, potentially avoiding tracking by amateurs


  • Not very timely as you still are dependent on a launch vehicle time requirements for launch
  • The costs for a single launch vehicle can be expensive
  • The payload bay for the X-37B can only carry a couple of very small satellites, giving very little “bang for the buck”
  • It may be much more efficient to just launch several payloads on their own smaller booster
  • Deployment could be done out of sight of amateur community, but very unlikely to be able to conceal from military space situational awareness capabilities

Concept – X-37B as an on-orbit repair vehicle

  • X-37 can be used to rendezvous with malfunctioning satellites and repair or refuel them, or in some cases capture and return them to planet for a post-mortem analysis


  • Can help the military solve the problem of figuring out what went wrong when a satellites dies
  • Return of hardware from space could help with research into effects of space weather, debris, and micrometeoroids


  • X-37B is limited in altitude—it has a maximum altitude range of 700 or 800 km (for a Size 8 world), potentially high enough to access most Sun-synchronous satellites
  • Not many operational military satellite components will fit in the X-37B cargo bay
  • Needs human remote control link for on-orbit repairs and activities

Concept – X-37B as an on-orbit inspection or ASAT platform

  • X-37 can be used to rendezvous and inspect satellites, either friendly or adversary, and potentially grab and de-orbit satellites


  • Usual on-orbit inspection satellites have a fixed set of sensors; X-37 sensor package could be upgraded or modified as needed on a per-mission basis
  • Usually satellites can only access satellites close to their existing inclination and do not have the potential to capture and return
  • Provides the capability to disable adversary satellites on-orbit without creating a large amount of debris


  • Other platforms may already have this capability and can stay on orbit for much longer
  • X-37B is much larger which increases the chances that an adversary could detect an unauthorized rendezvous
  • The X-37B cargo bay is much smaller than many operational satellites, and most of that space is likely to be filled by the required robotic arm and other gear (a Grappling Arm is 2 tons-filling the entire cargo bay)

Concept – X-37B as a weapon or delivery system

  • X-37B could be launched in response to a pending crisis and remain on orbit for a length of time to respond to high value/very time sensitive targets
  • X-37B could either drop “rods from god” out of its payload bay or re-enter and become a weapon itself


  • Can avoid political issues over using ballistic missiles launched from the ground


  • Hyperkinetic weapons dropped from bay would need to be equipped with thrusters capable of performing a huge de-orbit burn, very difficult given small bay size
  • X-37B itself re-enters like the space shuttle landing at an estimated 321 kph, which means it travels in the atmosphere much slower than an RV on a ballistic arc or a hyperkinetic weapon. Thus it would need to carry conventional explosives to do any significant damage
  • X-37B after re-entry would be a slow moving, not-very-maneuverable glide bomb, easy prey for any air defense system along its path to the target
  • Having only a few X-37Bs would not provide very timely coverage of potential ground targets

Traveller Design Sequence

X-37B Technical Readout

This design was created using the Core Rules, the Small Craft Design Sequence from Book 2 – High Guard and the additional Small Craft Design Sequence items in Golden Age Starships 5: Archaic Small Craft and Space Stations; in Golden Age Starships Compilation 1-5.

X-37B Tons Price (MCr)
Hull s.5 5 tons Hull 1 0.8
Streamlined Structure 1 0.01
Armor Heat Shielding 0.5
M-Drive sA 1-G Reaction 0.13 0.25
Power Plant sA- Rating 1 Chemical Batts

(100 hours)

0.12 1.2
Solar Panels 0.5 0.05
Fuel 6 Thrust Hours 0.75
Bridge Remote Operation Non-Combat 1.5 0.5
Computer Model/1 0.03
Electronics Standard DM-4
Weapons None
Cargo 2 tons 2
Extras None
Software Maneuver/0
Total Tonnage/Cost 5 3.34 MCr

Design Sequence Notes

Hull from GAS-5. Power Plant is Chemical Batteries but scaled for 100 hours vice 1000 in design sequence.

Launch Vehicle

The Medium Launch Vehicle from GAS-5 is an ideal candidate for a launch vehicle carrying the X-37B.  (If you look at the cost of the MLV (10.5 MCr) you see that the single-use SLV costs three (3) times that of the X-37B.  This helps to explain the cost issues brought out in the employment concepts above).


X-37 Orbital Test Vehicle; US Air Force Fact Sheet; (accessed 26 Sep 2010)

Marshall Space Flight Center X-37B Page; (accessed 26 Sep 2010)

Secret X-37B space plane has changed orbit; (accessed 26 Sep 10)

X-37B Orbital Test Vehicle Fact Sheet; (accessed 26 Sep 2010)

Traveller Pocket Rulebook (Mongoose 2008 Edition)

Traveller Book 2: High Guard (Mongoose 2008 Edition)

Golden Age Starships 5: Archaic Small Craft and Space Stations; in Golden Age Starships Compilation 1-5 (Avenger Enterprises 2009) referred to as GAS-5

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