Here’s why NASA and the Space Force are interested in pizza-shaped satellites

DiskSat's design offers "a power-to-weight ratio unmatched by traditional aluminum satellites."

See full article...

 

[dmsilev]

The DiskSats are 39 inches (1 meter) wide, about twice the diameter of a New York-style pizza, and measure just 1 inch (2.5 centimeters) thick.

I think technically that makes it an oversized Chicago style pizza.

Regardless, I approve of this new pizza-based units system.

 

[MST2.021K]

I think technically that makes it an oversized Chicago style pizza.

Regardless, I approve of this new pizza-based units system.

Surprisingly, Little Caesar's has already tackled the metric pizza unit: https://littlecaesarsksa.com/product/pizza-by-the-meter/

 

[liquid_actinide]

similar to SpaceX’s pioneering approach to launching stackable Starlink Internet satellites

Oh ffs, Spacex didn't invent everything.

Link to Orbcomm satellites description: an old article

 

[archtop]

Re: the reaction wheel -- I always thought that multiple reaction wheels were needed to keep a satellite stable (non-rotational) in three dimensions. These disk satellites look like they can only accommodate a single reaction wheel, leading to stability (non-rotation) in only one dimension. I'm sure I'm missing simething, but what?

 

[Missing Minute]

Re: the reaction wheel -- I always thought that multiple reaction wheels were needed to keep a satellite stable (non-rotational) in three dimensions. These disk satellites look like they can only accommodate a single reaction wheel, leading to stability (non-rotation) in only one dimension. I'm sure I'm missing simething, but what?

The satellites have at least one electronic thruster each so that could offer an additional degree of control.

 

[Missing Minute]

thicker air below 250 miles

TIL that while the matter at this altitude is technically air, it is very different from what we have at the surface, the composition is very different and is starting to behave less like a gas that has "pressure" and more like a collection of particles on ballistic trajectories.

Spoiler: Original flawed version

At that altitude the matter forming the heterosphere portion of the atmosphere, is not homogeneous, so it isn't air.

 

[freeskier93]

Re: the reaction wheel -- I always thought that multiple reaction wheels were needed to keep a satellite stable (non-rotational) in three dimensions. These disk satellites look like they can only accommodate a single reaction wheel, leading to stability (non-rotation) in only one dimension. I'm sure I'm missing simething, but what?

Where does it say there's only 1 reaction wheel? The article says reaction wheels, plural, so more than one.

 

[SpikeTheHobbitMage]

Where does it say there's only 1 reaction wheel? The article says reaction wheels, plural, so more than one.

One wheel in plane is obvious, but the satellite is only 1" thick. That doesn't leave a lot of room for the other two wheels unless they either have a very small diameter or are deployable, and I don't see anything like that in the picture.

 

[DavidEmami]

"It's not a question of where he grips it! It's a simple question of weight ratios!"

 

[bradley13]

99% of all those materials will burn in the atmosphere.
Burning in the atmosphere doesn't mean they will vanish but rather they will disperse in the air, fall down to earth and/or be breathed by animals and humans.

Hundreds of tons of space dust reach the earth every day. The contribution from satellites is negligible in comparison.

 

[shadowless]

Re: the reaction wheel -- I always thought that multiple reaction wheels were needed to keep a satellite stable (non-rotational) in three dimensions. These disk satellites look like they can only accommodate a single reaction wheel, leading to stability (non-rotation) in only one dimension. I'm sure I'm missing simething, but what?

The disksats are very light, so the reaction wheels also don't need to be very large. A quick googling tells me there are many commercial cubesat reaction wheel packages (with multiple wheels at different orientations) that would technically just fit in at or under 25 mm, and I'm sure nothing prevents thinner designs, especially if you separate the wheels to individual components.

 

[Chuckstar]

Re: the reaction wheel -- I always thought that multiple reaction wheels were needed to keep a satellite stable (non-rotational) in three dimensions. These disk satellites look like they can only accommodate a single reaction wheel, leading to stability (non-rotation) in only one dimension. I'm sure I'm missing simething, but what?

Small cubesat reaction wheels exist that are less than 1” in all dimensions.

 

[Chuckstar]

The disksats are very light, so the reaction wheels also don't need to be very large. A quick googling tells me there are many commercial cubesat reaction wheel packages (with multiple wheels at different orientations) that would technically just fit in at or under 25 mm, and I'm sure nothing prevents thinner designs, especially if you separate the wheels to individual components.

These things are wide, though, so the moment of inertia will be relatively large for their mass. But most uses would probably be using the wheels only for stabilization, rather than re-pointing, so won’t need large amounts of angular momentum storage.

 

[jenesuispasbavard]

Flying saucers, finally. Took us long enough.

 

[torp]

Flying saucers, finally. Took us long enough.

What if there's a glitch in their stabilization wheels and instead of moving through space they move through time, end up in the 50s and generate all those UFO reports we find in archives?

 

[wagnerrp]

Re: the reaction wheel -- I always thought that multiple reaction wheels were needed to keep a satellite stable (non-rotational) in three dimensions. These disk satellites look like they can only accommodate a single reaction wheel, leading to stability (non-rotation) in only one dimension. I'm sure I'm missing simething, but what?

They only need to be flat for launch. Reaction wheels could pivot into an appropriate axis after deployment.

 

[xeroks]

These disk satellites look like they can only accommodate a single reaction wheel, leading to stability (non-rotation) in only one dimension.

they're an inch thick, A reaction wheel with a diameter slightly less than that should be possible. Just need to spin it a faster. If the decreased diameter was causing efficiency issues, you could maybe angle them at 45 degrees.

Worst case, you could extend spokes at deployment or pivot to extend the wheels beyond the packaged thickness of the unit.

 

[xeroks]

Flying saucers, finally. Took us long enough.

we thought it was for aerodynamics or something when in fact it's because they're efficiently stacked on the mothership.

 

[ubercurmudgeon]

Hundreds of tons of space dust reach the earth every day. The contribution from satellites is negligible in comparison.

Currently negligible. Never underestimate the human race's ability to tip the balance of natural concentrations in a way that, in the long term, proves harmful to itself.

 

[worldeight]

This is one of those designs that seems obvious in retrospect.

I’m a space layman, but what are the consequences of discs being less agile? To me it would seem that there isn’t much significant adjustment for most satellites once they establish orbit.

 

[kurly_b]

I can't be the only one who keeps misreading it as DickSat.

Technically it’s a choad satellite

 

[KurtRoedeger]

The DiskSats are 39 inches (1 meter) wide, about twice the diameter of a New York-style pizza,

I see you included the metric measurement, but thank you for including the 'murican measurement with the pizza size.

 

[Speaking from Europe...]

These are the flying discs the government wants you to know about

I'm more interested in the flying discs the govt. does not want me to know about

 

[DCStone]

Doesn't a larger surface area facing the earth mean a brighter satellite in the sky? Not sure astronomers are going to be too happy if this takes off..

 

[Arcadia_Ego_24]

Ha. Pie in the sky.

 

[CrystalCowboy]

Continual pulsing from the satellites’ electric thrusters will allow the DiskSats to maintain altitude as they glide through the uppermost layers of the atmosphere.

Technically, if they are applying thrust, they are not 'gliding.'

I found some photos of the launch vehicle.
Foam disk launcher

 

[Cryxx]

that pic is an engineer, but they cannot be working on a disksat. What they are working on in the pic is waaay bigger than was described

 

[wagnerrp]

Doesn't a larger surface area facing the earth mean a brighter satellite in the sky? Not sure astronomers are going to be too happy if this takes off..

To a first order approximation, but that misses efforts to avoid effects. Starlink Gen2 is both significantly larger and significantly dimmer than Gen1. Somewhat counterintuitively, they’ve made the bottom highly reflective, and then actively steer the satellite to not reflect to Earth.

 

[Lexomatic]

Oh ffs, Spacex didn't invent everything.

Link to Orbcomm satellites description: an old article

To expand on that reference for TL;DR readers: Orbcomm (sometimes styled ORBCOMM) birds were launched like a stack of coins (or maybe pies, given their proportions). Using the Orbital Microstar satellite bus, the form factor was a fat disc (41" wide, 16" thick), with two circular solar panels that folded out to 90°, and a four-segment VHF/UHF antenna spar. The constellation (62 total including replacements) was launched from 1993 to 2015 via Taurus (two birds each), Pegasus (eight), Falcon 9 (up to 11), Russia's Kosmos (six), China's Long March 4B and India's PSLV.

See Wikipedia and ORBCOMM LLC's 2008 system overview (pdf).

 

[just another rmohns]

The disksats are very light, so the reaction wheels also don't need to be very large. A quick googling tells me there are many commercial cubesat reaction wheel packages (with multiple wheels at different orientations) that would technically just fit in at or under 25 mm, and I'm sure nothing prevents thinner designs, especially if you separate the wheels to individual components.

The fine article says disksats are about an inch thick, but is there any reason they can't be thicker when needed? For a tech demonstration, keeping everything to an inch thick is a good idea; it proves the system can work at minimum size. But if you needed thicker components, having an option for varying height units could be useful. As just one idea, you could deploy even larger antennae or solar panels to double or triple its width.

Also, if the disks' diameter is two PWU's (Pizza Width Unit) wide, thickness would then be about 1.5 PTUs (Pizza Thickness Unit).

I’m a space layman, but what are the consequences of discs being less agile? To me it would seem that there isn’t much significant adjustment for most satellites once they establish orbit.

Depends on your mission. The examples cited in the article include weather sensors and ground photography, which merely require it be pointed down.

that pic is an engineer, but they cannot be working on a disksat. What they are working on in the pic is waaay bigger than was described

Perspective. The stack is sitting on a table-height platform. The engineer is on their knees on the floor next to it. Their head is below the top of the stack.

The photo's distortion shows the camera had a wide angle lens. This will further exaggerate the apparent size difference of objects closer to the camera (top of the stack) vs further (engineer).

 

[stefan_lec]

Technically, if they are applying thrust, they are not 'gliding.'

I found some photos of the launch vehicle.
Foam disk launcher

Reminded me of this gem from my childhood:


View: https://youtu.be/ai_3z3TT3E4

 

[Yep It's Me]

I hope, one day, we see DiscSat rocket exteriors painted like PEZ dispensers. Let's have a little fun with our space activities!

Edit to say, yes I know PEZ aren't round. Just riffing on the dispensing method.

 

[fkaOld_one]

Two question that I’m sure engineers have considered and dealt with but not mentioned in the story: middle axis instability and radiative heat transfer. Rotation will tend to be stable around the short axis, but stabilization will be needed to prevent tumbling around either or both of the long axes. The large surface area is an asset for radiative cooling— which is good, since other kinds of heat transfer aren’t available for satellites.

 

[fryhole]

I hope, one day, we see DiscSat rocket exteriors painted like PEZ dispensers. Let's have a little fun with our space activities!

Edit to say, yes I know PEZ aren't round. Just riffing on the dispensing method.

Nothing wrong with your comment; seeing the "artist rendering" gave me the same thought > PEZ IN SPACE.

 

[fryhole]

The DiskSats are 39 inches (1 meter) wide, about twice the diameter of a New York-style pizza, and measure just 1 inch (2.5 centimeters) thick. Made of composite carbon fiber, each satellite carries solar cells, control avionics, reaction wheels, and an electric thruster to change and maintain altitude.

Not if you count the local pizza place near me - they serve up 36 inch pizzas as their "small".

 

[Dtiffster]

These things are wide, though, so the moment of inertia will be relatively large for their mass. But most uses would probably be using the wheels only for stabilization, rather than re-pointing, so won’t need large amounts of angular momentum storage.

The article does go out of its way to say that it is slow, and can't be used for agile pointing. I took that to mean for example it isn't slewing as it passes overhead of an observation target to avoid motion blur from fixed optics. For this the optics themselves would have to do the precision pointing. But it could be used to say keep it's underside always pointed at the Earth, thus doing a single rotation every orbit.