Comment by elihu
13 hours ago
The main reason is that generating energy in space is very cheap and easy due to how ridiculously effective solar panels are.
Someone mentioned in the comments on a similar article that sun synchronous orbits are a thing. This was a new one to me. Apparently there's a trick that takes advantage of the Earth not being a perfect sphere to cause an orbit to precess at the right rate that it matches the Earth's orbit around the sun. So, you can put a satellite into a low-Earth orbit that has continuous sunlight.
https://en.wikipedia.org/wiki/Sun-synchronous_orbit
Is this worth all the cost and complexity of lobbing a bunch of data centers into orbit? I have no idea. If electricity costs are what's dominating the datacenter costs that AI companies are currently paying, then I'm willing to at least concede that it might be plausible.
If I were being asked to invest in this scheme, I would want to hear a convincing argument why just deploying more solar panels and batteries on Earth to get cheap power isn't a better solution. But since it's not my money, then if Elon is convinced that this is a great idea then he's welcome to prove that he (or more importantly, the people who work for him) have actually got this figured out.
Let's assume your space solar panel is always in sun - so 8760 kWh per year from 1kWp.
In Spain, 1kWp of solar can expect to generate about 1800 kWh per year. There's a complication because seasonal difference is quite large - if we assume worst case generation (ie what happens in December), we get more like 65% of that, or 1170 kWh per year.
That means we need to overbuild our solar generation by about 7.5x to get the same amount of generation per year. Or 7.5kWp.
We then need some storage, because that generation shuts off at night. In December in Madrid the shortest day is about 9 hours, so we need 15 hours of storage. Assuming a 1kW load, that means 15kWh.
European wholesale solar panels are about €0.1/W - €100/kW. So our 7.5kWp is €750. A conservative estimate for batteries is €100/kWh. So our 15kWh is €1500. There's obviously other costs - inverters etc. But perhaps the total hardware cost is €3k for 1kW of off-grid solar.
A communications satellite like the Eurostar Neo satellite has a payload power of 22 kW and a launch mass of 4,500 kg. Assuming that's a reasonable assumption, that means about 204kg per kW. Current SpaceX launch costs are circa $1500 per kg - but they're targeting $100/kg or lower. That would give a launch cost of between $300k and $20k per kW of satellite power. That doesn't include the actual cost of the satellite itself - just the launch.
I just don't see how it will make sense for a long time. Even if SpaceX manage to drastically lower launch costs. Battery and solar costs have also been plummeting.
https://www.spaceconnectonline.com.au/manufacturing/4751-air...
https://www.nextbigfuture.com/2025/01/spacex-starship-roadma...
Thanks for the interesting calculations.
Is it reasonable to use Neo as a baseline? Modern Starlink satellites can weigh 800kg, or less than 20% of Neo. I see discussions suggesting they generate ~73kw for that mass. I guess because they aren't trying to blanket an entire continent in signal? Or, why are they so much more efficient than Neo?
Interestingly the idea of doing compute in space isn't a new one, it came up a few years ago pre-ChatGPT amongst people discussing the v2 satellite:
https://forum.nasaspaceflight.com/index.php?topic=58374.msg2...
Still, you make good points. Even if you assume much lighter satellites, the GPUs alone are very heavy. 700kg or so for a rack. Just the payload would be as heavy as the entire Starlink satellite.
Kind of a scary thought - a DC in space can't be stopped by protests or regulation
That could be one reason they want to do it. Maybe by using data from Palantir or harvested from Elon's work with DOGE, along with twitter user data and whatever else they can get, they want their AI to be the all-seeing eye of Sauron. (Which isn't too far from what the whole ad-tech industry is about in the first place.) Or they want to make sexually explicit deepfakes of everyone Elon doesn't like. Or they want to flood the internet with AI generated right-wing propaganda.