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  1. Y

    Coronavirus

    Masks may be a net negative, all else being equal. Norwegian government does not recommend using masks, as they irritate and cause you to touch your face more often. (I haven't seen anyone wearing a mask yet - we'll see how it goes.)
  2. Y

    Coronavirus

    I believe the less aggressive strain never left China. What seems to be the case is that it takes a while before light symptoms become life-threatening. That's why it's so infectious. You can be mostly okay for a week or two, infecting many others, and then, bam, it hits you like a ton of...
  3. Y

    100 kWh Battery Coming Soon to Model 3?

    It was quite implausible to arrive in the middle of 2018, and my statement has since been proven correct. I think the most recent indications are significantly more plausible. Battery tech is always moving forward. :)
  4. Y

    NASA Announcement for the Moon

    What exactly can we learn on the moon that is both: 1. Applicable to mars? 2. Not doable in LEO (or on earth), which is even cheaper and faster? I can't think of much. ISRU on the moon and mars is quite different. Environmental systems are currently done on the ISS. If we want to assess the...
  5. Y

    NASA Announcement for the Moon

    NASA has plenty of funding to go to Mars and/or the Moon. But they are forced to focus on silly things, like the LOP-G, and they are forced to pay for pork in SLS states and all sorts of other institutional issues. What would it take to land and return people from the moon? In Zubrins moon...
  6. Y

    Hydrogen vs. Battery

    In 2018, global car production was around 1.4% BEV. At a sustained 50% growth, the progression is something like this: 2019: 2.1% 2020: 3.15% 2021: 4.73% 2022: 7.09% 2023: 10.63% 2024: 15.95% 2025: 23.92% 2026: 35.88% 2027: 53.82% 2028: 80.73% 2029: 100% This may seem unlikely. But the roughly...
  7. Y

    Hydrogen vs. Battery

    True, I would guess the insurance cost for a hydrogen filling station is significant. Not only is the station itself quite expensive and not entirely unlikely to get destroyed in an explosion over it's lifetime, but you have to factor in the potential costs of blowing out windows in a radius of...
  8. Y

    Hydrogen vs. Battery

    Yes. Hydrogen cars use 3-5 times more energy than BEVs when running on hydrogen produced by electrolysis. So, if the cost of solar is say 10 cents/kWh, and a car does 4 miles per kWh, that's 2.5 cents/mile for BEV and 7.5-12.5 cents/mile for FCV. And then you can add the capital costs for...
  9. Y

    Hydrogen vs. Battery

    NEL (the supplier of the hydrogen filling station that blew up) has closed down the other two stations in Norway and another 8 across Denmark and other countries. (Not sure if US is affected, though it might be.) There's currently no place in Norway to fill hydrogen on a private vehicle. Though...
  10. Y

    Help requested on simple thruster calculation

    Ah, I don't think there are any official numbers on those.
  11. Y

    Help requested on simple thruster calculation

    81,000-212,000 lb, depending on throttle setting.
  12. Y

    NASA Announcement for the Moon

    It's an interesting thought. I'm sure it would be possible to get more performance out of Falcon 9 and Falcon Heavy, but it would be an engineering challenge. Basically it would mean a completely new second stage. Plus you would want to make a vacuum version of the Raptor, which is planned for...
  13. Y

    NASA Announcement for the Moon

    Maybe a little more than that. 48 tons CH4/LOX, 9 tons payload and 3 tons dry mass. Anything is possible. Though the changes would be so massive there wouldn't be much left of the original Falcon 9/Falcon Heavy... The question is how much effort SpaceX realistically would put into this lander...
  14. Y

    NASA Announcement for the Moon

    I can't quite figure out how they would be able to do 12 tons of payload to the surface of the moon using Falcon Heavy and NTO/MMH or kerolox (using a specific impulse of 310). It seems plausible if using hydrolox with a specific impulse of 450, though. Rough calculations: A 60 ton lander in...
  15. Y

    SpaceX Internet Satellite Network: Starlink

    If SpaceX allows unfiltered access to the internet in China, Musk will basically be blacklisted and can forget about doing business in China. Not just SpaceX, but also Tesla. So I'm fairly sure SpaceX will implement filtering, simply refuse links originating in China, or only allow links...
  16. Y

    SpaceX Internet Satellite Network: Starlink

    Look at the table on page 5/6 here: https://sma.nasa.gov/LaunchVehicle/assets/spacex-falcon-9-v1.2-data-sheet.pdf The 22.8 tons is specified at 185 km and 28.5 degrees inclination.
  17. Y

    SpaceX Internet Satellite Network: Starlink

    I'm not sure exactly what altitude the 22.8 tons to LEO are specified for, but I think it's something like a 185 km altitude at 28.5 degrees inclination. Going up to 550 km should then be a ~9% performance hit from my calculated 15 tons capability. But it's entirely possible the satellites are...
  18. Y

    SpaceX Internet Satellite Network: Starlink

    Interesting photo. One thing I noticed, is the new PAF (payload adapter fitting). I believe the standard one has a maximum of 10,886 kg, and I suppose this wider lower one would allow SpaceX to increase that substantially. (Maybe also usable for Falcon Heavy?) Being lower, I guess it also helps...
  19. Y

    Blue Origin: Future Plans

    Yeah, it isn't entirely straight forward to do the comparison. Recovering the center core of a Falcon Heavy is a bit like recovering the second stage of a different rocket. By the time it's out of fuel, it's gotten so much speed that landing it is a real challenge. You will land far out at sea...
  20. Y

    Blue Origin: Future Plans

    Might make sense to include the Falcon Heavy pricing with expended center core. If you expend the center core, you're talking more like $110m for 16T to GTO. That's cheaper per ton, which is a quite important metric. And full expendable mode you're talking $150m for 26.7T. Cheaper still, per...
  21. Y

    Commercial Crew Transportation Capability (CCtCap) SpaceX and Boeing developments

    Might not be a result of the salt. Could be related to: - Zero G for several days - Vacuum for several days - Reentry heating - Splashdown G-forces Fingers crossed it's something simple that's been overlooked, like a seal that wouldn't be expected to survive vaccum, or insufficient clearence...
  22. Y

    Blue Origin - Booster Reuse - New Shepard

    I'm sure it's possible to design for deep throttling ability, if they really want to be able to hover. Maybe have some sort of bypass from the combustion chamber, where instead of going through the nozzle, you just dump the gas.
  23. Y

    This must be the silliest reason to sell a Tesla

    The only experiment I've seen the results of concluded EMF radiation was basically the same in an EV as in an ICE vehicle. Most of the radiation comes from the metal fibers in the tires, where the rotation of the tires generates a magnetic field.
  24. Y

    Blue Origin - Booster Reuse - New Shepard

    Also the reason provided by Cosmacelf holds true. For maximum fuel efficiency, you want to wait as long as possible before initiating the landing burn, meaning you want to pull as many Gs as possible in the landing burn, and then perfectly have speed and height be zero at the same time. This...
  25. Y

    Blue Origin - Booster Reuse - New Shepard

    Was about to say the same thing, and it's still true, as far as I can determine. A single Merlin at 40% output still has around 38.4 metric tons of thrust, while an empty Falcon 9 first stage weighs something like 22 metric tons.
  26. Y

    Commercial Crew Transportation Capability (CCtCap) SpaceX and Boeing developments

    It will count against SpaceX if it was something that's likely unrelated to the capsule having visited space. SpaceX needs to find the cause before putting people in it. Though one can hope the fault *is* related to having visited space, as that would likely have have minimal impact on SpaceX...
  27. Y

    Model X catches fire for no reason

    Fire or crash damage to a battery pack can cause it to catch fire, even days after the event. As can improper handling of the vehicle, like jacking it up in the wrong place. These things can not be described as spontaneously catching fire. There is simply a delay between the event and the...
  28. Y

    Fuel Cells

    The thing is that if you use grid average electricity, a BEV will pollute maybe 50% as much as a comparable ICE vehicle. (Varies from place to place, but 50% isn't very wrong.) When you produce hydrogen from that same electricity, you need something like 3.5 times more electricity per mile, so...
  29. Y

    Falcon Heavy Flight #2 - Arabsat 6A - LC-39A

    Maybe SpaceX should just stop trying to recover the center core. There are some downsides to recovering it: 1. Center core needs more fuel for making a successful reentry than side boosters, as it's coming in a lot faster. 2. Center core still takes a beating with all that heating. Means more...
  30. Y

    Fuel Cells

    One can't know exactly what Tesla is and is not working on, but I think it's quite unlikely Tesla would be working on fuel cells. Fuel cells introduce all sorts of needless complexity, and are much less efficient than batteries.
  31. Y

    FSD refund attempt: Tesla rep is lying

    Yes, FSD can't be consider a preorder and refundable on that basis, for those who argued that, but Tesla has consistently said that FSD features are right around the corner. Those expectations go into the purchasing decision, and if people don't receive what they could reasonably have expected...
  32. Y

    Commercial Crew Transportation Capability (CCtCap) SpaceX and Boeing developments

    I tend to agree they will fly. But it's certainly not set in stone. Given sufficient delays, NASA would cancel their contract. Though it seems unlikely there will be sufficient delays, given the progress thus far.
  33. Y

    Wiki Falcon Super Heavy/Starship - General Development Discussion

    I hope they can get away with something like 10 different shaped tiles, rather than every tile being different (like the space shuttle). For the sylindrical parts of the Starship, they can probably get away with just one shape. The nose cone and the control surfaces will be a bigger challenge.
  34. Y

    Building the Full Metal Starship testbed: Starhopper

    That would be a crazy amount of gimbal range. Seriously doubt it. (And how would you realistically land with the rocket at something like a 20 degree angle?) That's my guess. Unless we see a second Raptor show up very soon.
  35. Y

    Building the Full Metal Starship testbed: Starhopper

    Doesn't look like that Raptor is centered. So will they install another one before the test, or will they do a small test where they aren't anywhere near lifting off? I guess we'll see soon.
  36. Y

    CRS 16 Booster Question

    I think the rocket gimbaling can in fact slow down the rotation, as the rocket is not rotating entirely vertically. As long as the axis of rotation is perfectly though the center of the booster, the gimbaling can't do anything, but if you suppose the axis of rotation had been shifted 90 degrees...
  37. Y

    SLS - On the Scent of Inevitable Capitulation

    Definitely. For one thing, the consequence of a failure would be approximately halved. If the first launch fails, you simply hold off on the second launch. If the second launch fails, you may still have time to prep a repeat before the payload of the first launch degrades in any way. Another...
  38. Y

    SLS - On the Scent of Inevitable Capitulation

    Ah, right, forgot that. But if EM-1 is done commercially, I think chances are good SLS is SOL for the remainder of the launches.
  39. Y

    SLS - On the Scent of Inevitable Capitulation

    Anyone really know what the Orion capsule does differently from Dragon 2? Seems like it's roughly the same size. Is there any reason (besides political) why you couldn't simply adapt the Orion service module to be compatible with the Dragon 2? Then you could launch a service module on a Falcon...
  40. Y

    SLS - On the Scent of Inevitable Capitulation

    If Orion were to be sent up with crew, that would mean crew-rating the Falcon Heavy. Not sure if this is where SpaceX would like to direct their energy. Though they could just launch Orion without crew on Falcon Heavy, then launch a Dragon 2 with crew and supplies. Seems a bit silly to launch...
  41. Y

    SpaceX F9 - Comm Crew DM-1 - LC-39A

    I haven't seen SpaceX specify anthing like that. But I would think you would want to wait as long as possible. Let the atmosphere do as much work as possible before spending precious fuel on slowing down. (The faster you're going, the more drag you have, and the more effective the braking.) So...
  42. Y

    SpaceX F9 - Comm Crew DM-1 - LC-39A

    Funny, I had the exact opposite reaction. Timed it to around 10 seconds between each callout, so about 10 m/s. That's still pretty fast - like 20-ish mph. If you have a car accident at 20 mph, you will feel sore. But the water and the seats probably help dampen the blow by quite a bit. I do...
  43. Y

    SpaceX F9 - Comm Crew DM-1 - LC-39A

    Requires much less energy and space to simply carry heads. And then they just plug them into cyborg bodies on the space station.
  44. Y

    SpaceX F9 - PSN 6 & SpaceIL Lunar Lander - SLC-4E

    Yes. Though one has to hope it doesn't happen again at a very inconvenient time. Like right before the landing burn!
  45. Y

    True mileage of a 100kw MX in winter switzerland

    I just use percent. And you'll get 3-5 km per percent with the X100D. So, if you have say 43% remaining, you can go between 43% x 3 km/% = 129 km (bad conditions, winter) and 43% x 5 km/% = 215 km (good conditions, summer).
  46. Y

    NASA Announcement for the Moon

    Basically no carbon on the moon. But it is possible to produce hydrogen and oxygen from water on the moon, at least.
  47. Y

    NASA Announcement for the Moon

    I thought the delta-V hit was less than that. But there can still be arguments for doing it this way. Assuming commercial launchers can *juust* reach LOP-G with worthwhile modules for a mars transit vehicle, and you need a human presence for assembly, it can be more practical to build it at...
  48. Y

    NASA Announcement for the Moon

    The delta-V requirements to go from the LOP-G to Mars transfer is something like half that of going from LEO to Mars transfer. This means that you could build a vessel at LOP-G, suitable for months in transit and which could be reusable for travel to/from Mars, and never go to deep into the...
  49. Y

    NASA Announcement for the Moon

    I don't think very much, if anything, is transferrable to a Mars mission. The architecture seems quite tailored to getting to moon surface. But you could of course use the LOP-G as a base for assembling a vehicle for going to Mars. I assume they would have a larger transit vehicle with a smaller...
  50. Y

    NASA Announcement for the Moon

    SpaceX shouldn't focus on anything that would be a distraction from Starlink, Starship and regular launch services. But maybe SpaceX could do something like adapt a Falcon 9 second stage to act as the decent vehicle. They might have some applicable data from their thoughts om landing their...

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