Mysterious X-37B spaceplane flies again, this time carrying a quantum GPS alternative The US military’s Boeing-built X-37B spaceplane is in space again for its eighth mission. The X-37B is an uncrewed craft that, just like the USA’s retired Space Shuttle, launches on a rocket and after re-entry makes an unpowered landing on a terrestrial runway. The vehicle has engines it can use to maneuver in space, but in …
Because there is an agreement between the grown-ups that we're not putting weapons in space. Because otherwise everyone else will and eventually somebody will misinterpret an accidental collision or rocket explosion and decide to take out all your satellites in response, or just put a satellite with 2tons of ball-bearings and a bit of gunpowder and say "well if I can't go up there - nobody can"
Grown ups? Really? We're not talking mine shaft gaps here, we're talking the ultimate high ground.
Sure, Rods from God are not going to happen, at least, not until we start mining asteroids, or at least the moon. But the US, Russia, China, India, France, and the UK have all demonstrated ASAT capabilities, and Israel has demonstrated all of the components. These are not bluffs, but warnings. Which is a far, far cry from assuming that a less GPS-dependent power is going to just let those birds keep singing. Note that you do NOT have to deorbit a GPS satellite to incapacitate it. No one, that I know of, has demonstrated this, but a strong EM would work just fine, almost no Kessler implications.
I'm quite certain that US war planning to defend Taiwan assumes that China will take out our GPS for that part of the world. It's part of why we have backups, after all.
"you do NOT have to deorbit a GPS satellite to incapacitate it. No one, that I know of, has demonstrated this, but a strong EM would work just fine"
You don't need to do anything to the satellites to disable GNSS. A GNSS will be able to deal with losing some satellites from the constellation, so you would have to disable several of them. But that said, it's still far easier to deny GNSS by jamming from within the atmosphere, or the ground.
However, note that GPS-style GNSS satellites (GPG, Glonass, Galilleo, Baidou) - with the exception of a couple of Baidou ones - are not geostationary; so individual satellites do not cover just some specific part of the world; although there are a few regional services.
although "hypersonic" in the context of weapons is generally taken to mean being able to do significant course alterations, as opposed to the rather predictable paths of fast moving but "simple" ballistic trajectories.
So the 1980s Pershing II qualifies? Its warhead deviated from a ballistic arc, making a hypersonic glide and a final, steered path to the target.
atom interferometry can be used to measure position
no, it can be used to measure acceleration. Like in "6-axis inertial measurement unit" where the 6 axes are 3 for linear acceleration and 3 in rotation around the 3 main axes X-Y-Z. It is meant to replace GPS when GPS is spoofed. One cannot measure speed with interferometry as that is what Michelson wanted to measure (the displacement speed of Earth in the Ether). But through acceleration one can measure the displacement of atoms.
As for rotation, it's possible to measure the rotation directly and not only the rotational acceleration (the physics involved is more complex to explain though : today, it's measured by interferometry in a spool of glassfiber, and when the device rotates in the direction of the spooling then the distance to travel in the fiber is slightly longer and can be measured by interferometry, when it rotates in the opposite direction the distance to travel is shorter).
The minuteman 3 can archive 200m strike accuracy anywhere in the world, and it uses inertial guidance from launch to impact. Trident D3 has an accuracy of 90m with inertial guidance but then it is much shorter range. The goal for the Sentinel missile is 50m CEP.
A detonation within 50 m is considered a guaranteed kill of a hardened silo, Trident D3 achieves this because it is 90m CEP but with multiple re-entry vehicles. Minuteman and Sentinel are single warhead.
Drift is the usual problem. If you can't meassure your position or velocity, you have to estimate the velocity based on the acceleration, and estimate position from that. Any inaccuracies grow over time. Inertial guidance is pretty good these days, but usually for short durations. I suspect this thing is in orbit to test the long term drift performance of this inertial navigation.
I was curious about the
"using a six-axis quantum inertial measurement unit"
Seemingly, three-axis measurement would cover x, y, and z. And, if you want to reach, a fourth axis could be covered by using a good (atomic or quantum) clock.
But, what about axes 5 and 6? Reminds me of a certain oscillation overthruster, Buckaroo Banzai, and Electroids from the Eighth Dimension.
Sorry, I digress. In classes I took, way back when, an "axis" was defined as a line, or if you prefer, a pair of vectors, that were 180 degrees apart.
I'm not sure whether a "spiral axis" would be considered canon (axis _of_ the spiral, yes, but, clockwise/counterclockwise or spin/anti-spin seem foreign to the concept of an axis, where up/down, left/right, near/far make more sense). Surely, there's a better name, or scheme, than lumping it in with "axis"? I mean, just by definition, "axis" seems too linear.
Perhaps "rotational degree of freedom" (or "RDOF", because, like kittens, who doesn't love acronyms?)
But... maybe that's what they call it, these days?
6-axis gives you 3 lateral movements in the x,y,z axes (forward/back, up/down, left/right, but facing the same direction, if you like a real world example), and then 3 rotational movements in the same axes (rotate left/right, look up/down, tilt left/right if you consider your head movements).
2014 NS article on similar tech for subs: “Today, if a submarine goes a day without a GPS fix we’ll have a navigation drift of the order of a kilometre when it surfaces,” The claim was Quantum Interferometry could get that down to a metre.
But it highlights its inability to separate inertial and gravitational acceleration. (Thanks Einstein.)
I'm going with "they're lying". First, NO WAY is any vaguely competent military going to spill such data. Second, I would be shocked if three gyroscopes, in 2014, would have such drift after compensation, and that doesn't take into account what an actual physicist could come up with.
I'm pretty certain that most submarines have for many years had a navigation periscope to allow them to check their position by looking at the stars (and probably pick up GPS information nowadays as well).
Of course, the submarine has to come near to the surface (a few 10s of metres), but not actually to the surface. The periscope will break the surface, but that can be difficult to detect unless you are in the immediate vicinity with the correct radar or mark-one eyeball looking at the right time. They are sill more vulnerable, as they are most safe hundreds of metres below the surface, and below a thermocline or two.
A sextant on a submersible is .. ahh ... impractical?
Just being silly, I had to check. There are sextants and navigation gear for scuba divers.
"and that doesn't take into account what an actual physicist could come up with."
The interferometry they're testing is exactly what actual physicists decided to come up with to fix the problem.
And, as an actual physicist, I've zero experience of using these things on land. And zero experience of using them underwater. So I've no clue as to how accurate inertial measurements can be. But in the ocean there will be currents which isn't a problem for land based uses so I wouldn't extrapolate.
Doing a bit more research. Here's a 2012 summary of atomic Interferometry. It says the best optical gyroscope has a loss of 0.0001°/h level. The g-field problem applies to some atomic gyroscopes. Other designs suffer from issues with the B-field...
SINS = Ship's Inertial Navigation Systems
I believe US submarines have been using it since the USS Skate (SSN-578)'s trip to the North Pole in 1959.
They didn't have GPS back in the 1950s/1960s, and, while SINS may have been +/- a KM or two, back then, it got better.
Current, actual drift would be highly classified, but, who wouldn't want their enemies to think it was +/- 1 KM? (Well, aside from those banking on MAD and the submerged leg of the triad.)
One detail of GPS, Galileo et al which is not mentioned:
The satellites don't simply *know* their positions. They're constantly ranged from a network of ground stations. The resulting ephimerides get frequently re-calculated and uplinked to the satellite. Without this correction, they become useless within days. Which happened to Galileo in 2019:
https://berthub.eu/articles/posts/galileo-accident/
So rather than taking out many satellites, why not going after the 2 (two) ground stations for Galileo. I guess the American military's GPS system can afford a few more. Probably still easier to eliminate their uplink stations than going after the space segment.
So rather than taking out many satellites, why not going after the 2 (two) ground stations for Galileo
Sending a missile or 2 to ground stations lacks any plausible deniability. While some "debris" colliding with a satellite is a tragic accident And it's so much more tragic when the debris from that collision takes out more satellites, the aggressor can even arrange to lose a few of their own redundant satellites to to deflect guilt.
The author wrote that the Space Shuttle was launched "on a rocket", though the shuttle itself was part of the rocket. The X-37B, on the other hand, was the payload of the rocket.
Side note about the shuttle - the shuttle could have carried a bit more payload had it used the SSME's instead of OMS engines for final insertion to orbit but that would have meant that the external tanks would have had uncontrolled re-entry and landing who knows where.
Quantum GPS is a misnomer. Did the author come up with that or was it in Boeing's PR package?
This is an inertial measurement unit. GPS is Global Positioning System. The technology described is neither Global or a Positioning System (by itself). A system based on inertial measurement can only provide position data if you have an accurate fix of your initial position.
Taking out satellites is a big Rubicon to cross, while jamming them is less likely to trigger a cascade of tit-for-tat space vandalism. It does make sense to do the sort of things they're doing with the new block of GPS satellites because the directional capabilities massively increase the power needed for effective jamming. This would necessitate an enemy force to either place their jammers closer to the front line (within range of more weapons systems) or increase the logistical inertia (think more generator trucks), harming their ability to move in response to incoming attacks.
