> fully reusable rockets are going to be one of the most important engineering achievements in human history
The number of implicit biases, assumptions, and unsubstantiatable assertions packed into that extremely confident sentence is frankly kind of impressive.
We have no idea how important reusable rockets will end up being, because we have no idea of what the future potential (economical or otherwise) space travel will have. Even Musk’s oft repeated (supposed) personal motivation for space travel (“protection of the species”) will ultimately hinge far more on other, far more important (and as of yet unrealized) technologies than reusable rockets.
Not to mention your implicit comparison of reusable rockets to literally every other extant technology. I mean really - transistors? The written word? RF comms? Indoor plumbing??
Fyi the unscented Kalman filter is both easier to implement than the EKF, and also avoids several of the requirements that come along with the need to linearize (such as the differentiability requirement mentioned in the article). Also (to me, at least) the UKF is conceptually much cleaner, as the whole point is to place the approximation in the parameterization of the distribution, rather than on the function operating on that distribution.
> A Starlink satellite uses about 5K Watts of solar power. It needs to dissipate around that amount (+ the sun power on it) just to operate.
The “+ solar power” part is the majority of the energy. Solar panel efficiency is only about 25-30% at beginning-of-life whereas typical albedos are effectively 100%. So your estimate is off by at least a factor of three.
Also, I’m not sure where you got 5 kw from. The area of the satellite is ~100 m2, which means they are intercepting over 100 kw of bolometric solar power.
Useful, extractable energy comes from a temperature differential, not just temperature itself. Once your system is at temperature equilibrium, you cant extract energy anymore and must shed that temperature as heat
This argument assumes that you only need to radiate away the energy that the solar actively turns into electricity, but you also need to dissipate all the excess heat that wasn’t converted. The solar bolometric flux at the earth is 1300 w/m2, or 2600 for 2 sq m. That works out to an efficiency of ~20% for your home solar, and your assumed value of 750 w yields an efficiency of ~30%, which is reasonable for space-rated solar. But assuming an overall albedo of ~5% that means that you were only accounting for a third of the total energy that needs to be radiated.
Put another way, 2 sq m intercepts 2600 w of solar power but only radiates ~1700 w at 350 k, which means it needs to be run at a higher temperature of nearly 125 celsius to achieve equilibrium.
Thats not how big-O notation works. You don’t know what proportionality constants are being hidden by the notation so you cant make any assertions about absolute runtimes
In most places in the US (california being a notable exception) taxes are reassessed regularly based on market conditions. In some areas this can result in the property taxes rising to an appreciable fraction of the mortgage rate - or in the GPs case, what the mortgage would have been, if they hadnt paid it off already.
> Happiness simply comes from other things in life than 'my castle my kingdom'.
I know its a typical US mindset (and far from US only) to have a house on your own, but its still an emotion
This is a frustratingly uninformed take. You are comparing apples to oranges by equating your decision-making process with that of someone in the US. The drive to own a house in the US is not just mediated by “emotion” - the calculus is fundamentally different than in many nordic countries. For instance, very few places in the US have rent control, which means that renting represents substantial risk of either experiencing a large increase in cost, or being forced to move at irregular intervals. On the other end of the spectrum, the US is one of the only places that offers 30 year mortgages, which means that (taxes and repairs aside) buying a home on credit still offers a high level of predictable cost over the long term.
Also, at least historically, there are very many places in the US for which housing is very affordable, given that the USs overall population density is so much lower than the average European country.
This is of course not to suggest that buying is always a good call - but it is often a logical and financially sound one.
Thats like saying the grocery store is ok with me eating some of the grapes while I shop so they must be ok with me walking out without paying for my groceries.
I’m not trying to be obtuse here. I really want to understand some sort of reasonable moral justification for actively avoiding paying for a service that you are using / circumventing the mechanism by which the business makes money.
Except in this case the only way the store makes money is either by you paying an entrance fee or by you looking at the products. You are being delivered a service (whose delivery costs money) while actively circumventing the mechanism the store employs to be compensated for that service.
I would genuinely like to understand this perspective. Ads or paying for premium is how the underlying business makes money. The UX might suck but you have a choice - you can just not watch YouTube. The approach you describe (which i understand is a popular one) is equivalent to justifying robbing a store because their prices are too high.
A slightly stronger (and more relevant) statement is that the number of mutually nearly orthogonal vectors you can simultaneously pack into an N dimensional space is exponential in N. Here “mutually nearly orthogonal” can be formally defined as: choose some threshold epsilon>0 - the set S of unit vectors is nearly mutually orthogonal if the maximum of the pairwise dot products of between all members if S is less than epsilon. The statement of the exponential growth of the size of this set with N is (amazingly) independent of the value of epsilon (although the rate of growth does obviously depend on that value).
> How much of a chance do you think we have of meaningfully changing a government, if they can guess with 80% degree accuracy how everyone voted, based on their chats and social networks
This doesnt really detract from your overall point, but you may be underestimating how easy it already is for the government to tell how you will vote, without use of networking information. Just knowing someone’s educational level and zip code is enough to guess their voting preferences to a high degree of accuracy (the latter component being the reason why gerrymandering is so effective).
I would still say its completely wrong, given that this explanation makes explicit predictions that are falsifiable, eg, that airplanes could not fly upside down (they can!).
While I agree with your general assessment, I think your conclusion is a bit off. You’re assuming 1kw/m^2, which is only true with the sun directly overhead. A real-world solar setup gets hit with several factors of cosine (related to roof pitch, time of day, day of year, and latitude) that conspire to reduce the total output.
For example, my 50 sq m set up, at -29 deg latitude, generated your estimated 30 kwh/day output. I have panels with ~20% efficiency, suggesting that at 60% efficiency, the average household would only get to around half their energy needs with 10 sq m.
Yes, solar has the potential to drastically reduce energy costs, but even with free energy storage, individual households aren’t likely to achieve self sustainability.
The number of implicit biases, assumptions, and unsubstantiatable assertions packed into that extremely confident sentence is frankly kind of impressive.
We have no idea how important reusable rockets will end up being, because we have no idea of what the future potential (economical or otherwise) space travel will have. Even Musk’s oft repeated (supposed) personal motivation for space travel (“protection of the species”) will ultimately hinge far more on other, far more important (and as of yet unrealized) technologies than reusable rockets.
Not to mention your implicit comparison of reusable rockets to literally every other extant technology. I mean really - transistors? The written word? RF comms? Indoor plumbing??