When I started my original series of posts on space battles, I speculated about what a combat-spacecraft designer might want to do in order to make a vehicle that could avoid enemy detection:
It would make sense to build their outer hulls in a faceted manner, to reduce their radar cross-section. Basically, picture a bigger, armored version of the lunar module.
Almost immediately, I got some feedback pointing me to the “Project Rho” website, which declares quite bluntly that “there ain’t no stealth in space.” The argument goes basically like this: any device you put on a spacecraft has to obey the second law of thermodynamics, which means that it generates waste heat. This heat will raise the temperature of your spacecraft well above the background temperature of ambient space (about 2.7 Kelvin). Therefore, the spacecraft will radiate and will be visible to infrared sensors, no matter what. Therefore, stealth combat spacecraft are impossible.
This argument is fundamentally sound. The principles are correct: you can build a detector that could locate any spacecraft. What I don’t like about this argument is its implied definition of the word “stealth” as “total invisibility.” Yes, it is possible that the detector you build will locate a stealthy space-fighter eventually. That clock is always ticking. But your adversary’s stealthiness can still pay off – if they get to launch their missiles before you spot them!
Later on, when I revisited space-battle physics, I went into a little more detail about possible stealthing technologies for spacecraft. In another post, I thought about some of the thermal concerns our hypothetical space-fighter designer would run into in trying to make the fighter hard to detect.
But the proof, as they say, is in the pudding.
There’s a military aphorism (Wikipedia tells me that Helmuth von Moltke is responsible) that battle plans never survive contact with the enemy. I suspect that, for all anyone’s speculations about what can, cannot, will, will not, or might happen in space combat, if we ever did find ourselves in a space war we would very quickly learn an entirely different set of guiding principles. Whether or not stealth spacecraft are possible will be apparent then, after the fact, no matter what arguments we make today.
However, we can get some insight by asking the question: do any stealth spacecraft exist today?
The answer, as it turns out, is “yes.”
Weather permitting, we are coming up on the launch of a Delta IV Heavy – a gargantuan behemoth leviathan giant of a rocket – carrying a National Reconnaissance Office “spy” satellite with the cryptic designation of NROL-15. Quoting a civilian military space analyst, AmericaSpace reports that the vehicle
is likely the No. 3 Misty stealth version of the Advanced KH-11 digital imaging reconnaissance satellite. It is designed to operate totally undetected in about a 435 mi. high orbit.
The article includes some description (or speculation?) about the physical appearance of the stealth spacecraft, too:
Looking somewhat like a stubby Hubble space telescope stuffed in an giant F-117 stealth fighter with diverse angles to reflect radar signals in directions other than back to receivers on the ground, Misty 3 is also covered in deep black materials designed to absorb so much light that it can not be tracked optically from the ground.
These design aspects are a huge challenge for a satellite that must also deploy solar arrays to generate electrical power and have reflective surfaces to reject heat. … The satellite may actually change shape to reflect heat when not over hostile countries trying to break its cover.
Apparently, there may also be some tricky maneuvering by the launch vehicle – to disguise the final orbit trajectory of the satellite. There is some speculation at the end of the article about the various options the vehicle might take to pull off that feat of obfuscation.
The bottom line for science fiction: cloaking devices are probably not going to work. But are stealth spacecraft possible or not? Well…we’re already doing it.
