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ddahlenon Mass Driver: Solar system routing mini-game

Its a fun mini-game, but your ceres is flying. I suspect there is a speed issue there. Here is it moving at accurate speeds: https://dahlend.github.io/ketev/#t=2026-10-10.2621&sel=1&v=4...

ddahlenon Show HN: Real-time Solar System with 526k asteroids and all tracked satellites

How are you sourcing the spacecraft positions from JPL? Are you just grabbing a huge list of state vectors?

My old day job was to compute asteroid positions for NASA telescopes, if you are interested in orbit prop you may be interested in: https://github.com/dahlend/kete

I made an asteroid only version of yours earlier this year, where it does full orbit propagation in workers: https://dahlend.github.io/ketev/

ddahlenon Comet SWAN26Q – The unconfirmed Scout object warrants monitoring, not concern

Thanks but I have no interest, I already have my own viewer:

dahlend.github.io/ketev/

ddahlenon Comet SWAN26Q – The unconfirmed Scout object warrants monitoring, not concern

Hi, I wrote orbit propagation code that is used to compute asteroids and comet positions for several of the NASA space telescopes.

I refit the orbit and yeah this is not a dangerous object. Given its (currently poorly constrained) orbit it is likely a comet, it came the closest it will ever come to Earth last month at about half an AU from us. (IE: half the distance from the earth to the sun).

It is at about a 110 degree inclination, meaning it is basically perpendicular to the solar system plane and already passed perihelion.

MOID, or Minimum Orbital Intersection Distance, is a basic geometric measurement that says how close the geometric ellipses of two orbits get together. It doesnt mean that the objects will actually be that close ever. For example the MOID of the jupiter trojan asteroids is basically 0 since the orbits are the same, but they dont get close to jupiter. It's really handy to use it to rule out dangerous stuff though, non-zero MOID usually means there is no way it could ever be dangerous.

Here is some of the orbit code I used: https://github.com/dahlend/kete

ddahlenon Ask HN: What are you working on? (September 2026)

This is very niche, only for people who do astrophotography or astronomers, mostly because of the required specialized file format.

I have slowly built out a set of tools for asteroid orbits and photometry (measuring how bright stars/asteroids are).

It is very rough still (Desktop only), and it only supports the FITs file standard.

https://www.astrometry.space/

Basically it is a full professional grade telescope processing pipeline in your browser. It does 2 queries to some custom databases to identify known asteroids and stars, but all image processing and calculations are done in the browser. This means the backend is pretty tiny. That said it is running on an old box in my closet, so queries may take a while if it gets hammered.

I built it since I have worked with quite a few astronomers over the past 4 years and I keep watching them do the same steps, purely built to make my friends lives easier. I wrote it all in rust and managed to compile it into wasm. With some help from fable as I am not a frontend guy at all, I built it into a small website.

Some of the code is public, the orbital mechanics code I wrote while I worked at Caltech. Which is being used on SphereX, NEO Surveyor, and the Roman telescopes to identify known asteroids. https://github.com/dahlend/kete

ddahlenon Claude Fable 5.1 and Claude Mythos 5.1

The writing style has significantly improved, however the token burn rate for tasks I have been working on seems to have skyrocketed. It definitely appears more capable (though I am unclear how much of that is just me liking the English it writes now vs actually more performant). I was using Fable 5 for some mathematical analysis assistance and redoing a part of it with 5.1 burned 60% of my session at a much faster rate.

ddahlenon FCC approves test of space mirror to light night sky

Strictly from an energy conservation argument this doesnt make a whole lot of sense to me. Just some back of the envelope math if they take their current mirror size, make 50k of them and overlap all of the output on the same 3 mile spot (the spot size they claim they will get on a single mirror). With an ideal reflector it is still less than mid-day daylight. Thats 50k satellites to give you direct sun over one 3 mile spot.

I suppose to make this feasible they would have to up the size of the mirrors. Unless this is somehow dirt cheap I can't imagine farmers or solar operators buying this.

ddahlenon Let's Destroy American Science

You can put in a public comment on these changes here:

https://www.federalregister.gov/documents/2026/05/29/2026-10...

ddahlenon Ask HN: What are tools you have made for yourself since the advent of AI?

I am a researcher studying orbital dynamics of asteroids/comets/dust. I made a very precise visualization tool for the solar system, it shows the motion of all of the known asteroids. When you click on a specific asteroid it will then show the hyper precise orbit for it which matches JPL's orbit calculations (full physics, n-body, relativity, non-spherical planets).

Not mobile friendly

https://dahlend.github.io/ketev/

ddahlenon Ask HN: What are you working on? (May 2026)

Research grade orbital mechanics, specifically of asteroids/comets. I've been working on it for 4 years now, finally tried using some AI tooling the last few months and ended up vibe coding a fun little visualization.

(Desktop Strongly recommended) https://dahlend.github.io/ketev/

ddahlenon Ask HN: What are you working on? (September 2025)

I suggest the appendix of the arxiv paper if you want to see some of the math required for solar system objects beyond simple Newtonian gravity (like Relativity corrections). I wrote that section specifically because I found it a pain in the ass to source those equations in literature.

ddahlenon Ask HN: What are you working on? (September 2025)

Its an implementation of a pretty standard integrator used by astronomers informally called "RADAU", but it is not exactly the same RADAU you would find elsewhere. Basically it is about as good as you can typically get for multi-step integrators, tuned for speed not precision though.

Note that how the code is laid out you cant really simulate non-solar system masses. Its really aimed at massless objects in the solar system, your 3-body simulations are actually quite difficult to do given the design.

ddahlenon Ask HN: What are you working on? (September 2025)

Working on orbital dynamics code for my PhD in astronomy, written in rust, it can accurately calculate the positions of all asteroids/comets to within a few meters. Today I am adding a new numerical integration method which should enable me to predict orbits from observations.

https://github.com/dahlend/kete

I'm working on modeling the motion of observed dust particles coming off of comet 67P, here is are some example 3d plots:

Example of rocks ejected from one position and their possible motions: https://dahlend.github.io/67p_beta_dust.html

Trying to determine possible orbits from a set of observations (the straight lines): https://dahlend.github.io/67p_dust_orbit.html

Shout out to pyvista for making these great 3d plots possible, a little less ergonomic than matplotlib, but it can export directly to html.

ddahlenon New Quasi-Moon Discovered Orbiting Earth, but It's Been Around for Decades

Here you go, here is its orbit from 1900 to 2100 in the earth's rotating frame, sun is at -1 on the x axis.

https://dahlend.github.io/2025_PN7_Orbit_1900-2100.png

Its hanging out for a while near us.

Shameless plug for my software I used compute it:

https://github.com/dahlend/kete

ddahlenon Kirkwood Gap Facts for Kids

I made a 3D visualization of this a few weeks ago:

https://dahlend.github.io/the_belt.html

This includes about 1.3 million known asteroids (most of the known ones), so the page is like 45mb. Consider yourself warned.

This is a plot of semi major axis, orbital eccentricity, and inclination of the orbit. The blobs are collisional groups, where a bigger rock(s) got smashed into 'families' of asteroids. Color is by the absolute magnitude H, which is a normalized, log scaled, brightness measurement. Typically smaller H means larger object.

You can see the Kirkwood gaps clearly along one axis, but as you move around you can see more complex orbital resonances. These resonances pump energy into or out of the orbit of the asteroid, causing them to leave the resonance after some time, depleting the region of phase space.

Source: I do solar system simulations for my PhD work.

ddahlenon Resizing images in Rust, now with EXIF orientation support

One good reason to keep the raw data and orientation separate is hardware calibrations. I see some discussion here along the lines of "why not just flip the data before saving it", and one counter-argument is that you should store the flip metadata anyways, as it important to trace which hardware pixel corresponds to which stored pixel. I realize this information is not vital for everyone, but it is super useful in fields where you need to characterize the hardware performance at the pixel level (for example astronomy).

ddahlenon Astrophysics Source Code Library

There are quite a few open source projects in astronomy, but in my experience there is a tremendous amount of code that is squirrelled away as it is difficult to reproduce and entrenches peoples positions. I have mixed feelings about this in general, as I understand the incentive structures, but I do wish in general some of the sub fields were a bit more open. I do think things are getting better in general.

Also I fully agree with the "codes" rant.

Source: working professionally in the field for 4 years.

ddahlenon Custom telescope mount using harmonic drives and ESP32

I am a professional astronomer, and I am running a survey for asteroids. This needs to be controlled from python, as it decides every night which objects to observe.

I also heavily use Jupyter for analysis, and with this code I can take over the telescope and command it in a jupyter session, allowing me to do live data analysis.

ddahlenon A general Fortran code for solutions of problems in space mechanics [pdf]

https://www.cambridge.org/core/journals/international-astron...

Here is a heavily used method in astronomy, this involves a higher order polynomial expansion than RK4.

This method has been extended a few times, my code uses a variation of it, and I know of several other projects which are also descended from it.

ddahlenon Custom telescope mount using harmonic drives and ESP32

This is really impressive! I considered buying a big harmonic drive mount for my scope, but the cost is really prohibitive.

I have experienced the pain of getting ekos/kstars/indi tools to work well on my personal scope. If you want to try driving indi devices via python I have some python code (it's not super polished, but it does enough for my needs): https://github.com/dahlend/contindi

ddahlenon A general Fortran code for solutions of problems in space mechanics [pdf]

It is neat to see some of the old work done in the field, this looks like a pretty classic treatment of the topic. It looks like they were using a fourth-order Runge-Kutta integrator, which would likely limit long term integrations accuracy (though looks sufficient for their use case). Many algorithms I have seen typically use much higher order integration methods to beat down the accumulation of numerical error.

Source: Working on my PhD in orbital mechanics of asteroids/comets, here are my open source (python/rust) orbital integration tools: https://github.com/dahlend/kete

ddahlenon Astronomers race to study interstellar interloper

Final edits of a paper at the moment, aim to submit next week. Perturbers are easy to add, though a little poorly documented at the moment. Additional physics right now are J2 of jupiter/sun/earth, and GR corrections for the sun and jupiter.

Biggest speed gain is that I have a custom SPICE reader that is multi-core friendly (I re-implemented a lot of the SPICE standard in rust), and it is used as the source for planet positions. Being able to skip planet integration leads to massive speedups.

ddahlenon Astronomers race to study interstellar interloper

I wrote a custom implementation of the Radau integrator, its been heavily modified. I have a lot of additional physics, it supports the non-gravitational models that JPL Horizons defaults to, so diurnal yarkovsky at least. I've been using it to study dust and small object dynamics, as they get pushed around by the sun a lot.

It does an OK job for impactors, but the integrator is tuned heavily for performance, and the tolerance defaults are not great for impactors.

I match jpl horizons for apophis to a few km, they have a lot more intense earth gravitational model then I care to implement, and by default I only include the 5 heaviest main belt asteroids, they have many more. That was the sweet spot for accuracy vs speed for me, overall accuracy goal is less than a few km over a decade.

The goal is to be able to handle the huge influx of new asteroids that the catalog will have due to LSST and eventually NEO Surveyor (which I worked on for 3 years). Most systems I know have been throwing hardware at the problem, I tried to make fast and efficient enough software that we can use it on a laptop for 5-10 million asteroids.

ddahlenon Astronomers race to study interstellar interloper

Different goals, kete is meant to be aimed more toward observers and telescope data processing, all asteroids and comets at once on a laptop. Short term analysis (<100 years) and speed are the priority.

ddahlenon Astronomers race to study interstellar interloper

Oort cloud comets are so distant that they are only weakly gravitationally bound to the solar system. When they come in and we see them, they have enough energy to go back out to the extreme distances. Minor nudges from the big planets are enough to cause them to become ejected from the solar system (ecc>1). This can lead to the whole "one and done" thing.

ddahlenon Astronomers race to study interstellar interloper

Eccentricity!

You can approximate the orbits of basically everything in the solar system using 2-body mechanics (IE, ignore the planets). If you do this you get orbits which are elliptical (eccentricity <1), parabolic (eccentricity = 1), or hyperbolic (eccentricity>1).

If the object has an eccentricity above 1, its not bound to the solar system.

Many long period comets have eccentricity hovering near 1, often these long period comets will be on their first pass (sometimes only pass) through the solar system. These comets though usually dont get much above eccentricity of 1. The 3 interstellars we have spotted have had like 1.2 or bigger. This one is above eccentricity 6! Its moving fast.

Edit: I have heard that when the first interstellar was found it actually broke a lot of peoples code, as it was common to hard code limits to allowed eccentricities (or simply not support ecc>1 at all).

ddahlenon Astronomers race to study interstellar interloper

I'm one of those astronomers! I'm working on my PhD in orbital dynamics.

A lot of people are requesting discretionary time on telescopes trying to get observations in. The orbit will put us on the other side of the sun when 3I is nearest the sun in october, we can see it now and after it comes back out from behind the sun.

Unfortunately, right now the it is in a very crowded star field (IE, its close to the galactic plane, lots of stars in the background).

If you are interested in orbital dynamics, I have an open source rust/python package for accurate orbital calculations of asteroids/comets:

https://github.com/dahlend/kete

ddahlenon Astronomers discover 3I/ATLAS – Third interstellar object to visit Solar System

This orbit visualization uses a simple 2 body approximation, so only the sun. This is because unless an object has a VERY close approach to a planet the two body approximation is more then enough for this style of visualization.

I did a full proper n-body integration and it is not visually different than this.

ddahlenon Astronomers discover 3I/ATLAS – Third interstellar object to visit Solar System

The closest it will come is Mars, but when I say close these are quite literally astronomical distances, about 0.2 au from Mars. This is about 75x further than the moon is from the Earth.

If it is an inactive rock, then we will not see it as any more than a point of light during its visit.