The Mars Helicopter Is Online and Getting Ready to Fly

In more modern weapons, imaging IR sensors are well-established for terminal guidance on missiles like LRASM, JASSM, or NSM to distinguish targets from clutter and identify specific target features (specific parts of a ship, for example). Of course "traditional" "IR-homing" SAMs and AAMs now use imaging sensors (often with multiple modes like IR+UV) to distinguish between the target and decoys/jammers. Even your basic shoulder-fired anti-tank missile like Javelin requires some amount of CV to identify and track a moving target.

I believe this is incorrect. From an earlier HN discussion:

"The 1202s were also a lot less benign than is often reported. They occurred because of the fixed two-second guidance cycle in the landing software. That is, once every two seconds, a job called the SERVICER would start. SERVICER had many tasks during the landing. In order: navigation, guidance, commanding throttle, commanding attitude, and updating displays. With an excessive load as caused by the CDU, new SERVICERs were starting before old ones could finish. Eventually there would be two many old SERVICERs hanging around, and when the time came to start a new one, there would be no slots for new jobs available. When this happened, the EXECUTIVE (job scheduler) would issue a 1201 or 1202 alarm and cause a soft restart of the computer. Every job and task was flushed, and the computer started up fresh, resuming from its last checkpoint. It was essentially a full-on crash and restart, rather than a graceful cancellation of a few jobs. And unlike is often said, the computer wasn't dropping low-priority things; it was failing to complete the most critical job of the landing, the SERVICER.

Luckily, the load was light enough that of the SERVICER's duties, the old SERVICER was usually in the final display updating code when it got preempted by a new SERVICER. This caused times in the descent when the display stopped updating entirely, but the flight proceeded mostly as usual. However, with slightly more load, it was fully possible that the SERVICER could have been preempted in the attitude control portion of the code, or worse yet, the throttle control portion. Since each SERVICER shared the same memory location as the last one (since there was only ever supposed to be one running at a time), this could lead to violent attitude or throttle excursions, which would have certainly called for an abort. Luckily, this didn't happen -- and the flight controllers didn't abort the mission not because 1202s were always safe, but because they didn't understand just how bad it could be, were the load just a tiny bit higher."

[1] https://news.ycombinator.com/item?id=20791307

Most of my knowledge of the subject is from a friend who did his PhD dissertation on it; specifically, triply-redundant adder circuits for single-bit operations, allowing for some rad-hard chip designs using regular foundry processes.

I wonder how one could use micro kernels to further improve startup time and have a mini distributed OS/kernel for each component.

You still have 10% the surface area, power usage and weight and 10 times the speed of the radiation hardened ones.

In microelectronics, costs are directly proportional to the die area. Actually, they might rise faster due to yield issues.

Making masks [1] is expensive. The bigger the mask, the more expensive. A mask set for a modern CPU can easily be in the millions, I think. And it gets more expensive with size.

Then you have yield. The bigger the chip, the more likely it has some defects (due to dust or other issues during fabrication). Often, processes work more or less well across a wafer: temperature higher in the center, etc. That can affect performance.

Due to yields, bigger chips have to be scrapped more often, and are generally less performant. Binning (selecting the fastest, slowest, more efficient, or chips with specific intact features across a wafer) is less effective. You might have to add redundancy or mechanisms to cut power to damaged areas to avoid short circuits.

Now, that's why we don't generally make bigger integrated circuits. Now, we could make bigger integrated circuits with today's latest clean rooms and equipment to try to raise yields. I don't know if that's being done already, but it would likely raise costs. On the other hand, progress is being made on bigger chips as well [2].

Another more promising direction (IMO) is to use chiplets like AMD does it. You could use more of these for a bigger virtual size.

Now, like I wrote, a lot of the performance improvements actually come down from physically scaling down the transistors: if the gate is smaller, the transistor needs less electrons to charge up. That means faster transistors, and less energy. Also, transistors are closer, so signals reach the next one faster [3].

If you want bigger chips at a previous technological node, you are going to need a huge heatsink, or disable part of the chip ("dark silicon") [4].

The real answer might come from completely different architectures, based on light or spin, or more power-efficient circuit/computer architectures like with adiabatic computing [5] (or non von neumann based, closer to what I do).

Power efficiency is key, since that's the limiting factor for performance nowadays (ask any overclocker: you don't want to melt your CPU. Also, rovers have a small energy budget). With better efficiency, you have room to grow performance again.

Paradoxally, software seems headed in the other direction, generally speaking.

[1] https://en.wikipedia.org/wiki/Photomask

[2] https://news.ycombinator.com/item?id=20739408

[3] https://en.wikipedia.org/wiki/Dennard_scaling

[4] https://en.wikipedia.org/wiki/Dark_silicon

[5] https://en.wikipedia.org/wiki/Adiabatic_circuit

1% is an arbitrary threshold and solar orbit is dependent on external circumstances rather than the Earth-Moon system itself.

On the subject of Sci-Fi, there's also a vacuum airship featured in one of Edgar Rice Burroughs' Tarzan novels - 'Tarzan at the Earth's Core'. It is of course much less scientific than Stephenson's version though.

Square-cube law. Mass scales with surface area, lift scales with volume. Large balloons (conventional, not vacuum) are simpler and more efficient than small ones.

As to materials, a tremendous problem with areogels are that they're exceedingly friable. Any friction, flexing, or stress will crumble the gell to a powder. I suspect this is why the gel hasn't taken off as it had been projected to. I did some very-early 1990s work in the space and aerogels were a noted emerging technology thought to have applications in, e.g., mobile home, pre-fab housing, and RV designs. For the most part, fibre-based insulation or expanded-foam (polystyrene) insulation remains the standard, largely because road and other vibration don't reduce your insulation to a few inches of fine dust at the bottom of wall cavities.

Material properties are complex, and represent interesting trade-offs between afforded capabilities and imposed constraints.

High quality 30fps video was never really an option but it's entirely possible/likely to get navcam video after a flight. The Snapdragon is also fast enough to do intraframe compression codec (even h.264) for the navcam video to be able to stream it live back to the rover for relaying back to Earth later like was done with the landing imagery.

The nature of Perseverance relaying through orbiters for high speed uplink to Earth was always going to preclude "live" video from any instrument. The only data important enough for "live" transmission is vehicle telemetry and even then that's only available for the portion of a sol (Martian sidereal day) that Earth is visible from the rover.