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Posts posted by Terwin

  1. 1 hour ago, sevenperforce said:


    Average acceleration isn't significantly different than an ordinary vehicle so the fairing is not a big deal.

    The fairing would not be for aerodynamics, but to protect the vessel from the heat and radiation.  This is not an issue in space because the pusher-plate acts as an umbrella and there is nothing else to redirect it.

    In atmosphere, the pressure-wave becomes an issue that the pusher plate cannot stop as it will engulf the entire vessel.  The pressure wave is also bringing lots of vessel melting heat and any radiation that misses the pusher plate can bounce off air molecules and radiate the vessel.

    The 'fairing' needs to resist the shock-wave, heat and radiation of many near-by nuclear blasts and likely needs to be even thicker than the pusher plate to do that.

  2. Nuclear pulse propulsion works in space because the pusher-plate works as a shield.

    In atmosphere, the heat an radiation can bounce off of air in addition to conduction and other methods of heat propagation that are not an issue in space.

    While a ground-launch Orion is more realistic than a star-trek shuttle, you would need a fairing that probably weighs more than the rest of the ship put together to have anything survive to orbit, and even that would be highly questionable.

  3. 7 hours ago, sevenperforce said:

    If you're proposing some sort of solution, then it's not enough to say "X failed, therefore Y." You need to properly characterize the nature of the review process failure and explain what sort of corrections to the review process are necessary to prevent not only this specific failure but any other known or unknown unknowns. 

    Are you suggesting that yelling 'do better' on the internet after an experimental vehicle launch with no crew or payload experienced anomalies that did not injure any of the many many bystanders is an insufficient argument to tear-down and rebuild from scratch every involved agency and organization?!?!??!

    Clearly every technical failure requires that we abandon all faulty technologies and start over with wood and bone tools!


  4. 1 hour ago, Arugela said:

    I'm still not sure on the aerodynamics. Could an ssto plane with 0.5 thrust to weight make it to orbit?

    I expect, that in-theory, with infinite dV and arbitrarily good aerodynamics, you could get just about anything that is able to get off the ground into orbit.  Thus far, in the real world, we have not been able to demonstrate any vessel getting into orbit without at least one stage with TWR > 1.


    Hydrolox is great in space for its specific impulse, but not so good for a first stage due to it's lower thrust.

    While it can work(see delta IV heavy), it is not common to have a pure hydrolox first stage for this reason.

  5. 2 hours ago, JoeSchmuckatelli said:

    Why not guess we are in a bubble of time - only able to resolve stars 13 billion years away in all directions - and that the universe may be wider and older than we can see?  (Why presume 13 billion years of visible redshift = age of everything?) 

    I thought the 13 billion year estimate was based on calculations related to the microwave background temperature, not visible red-shift.

    I am pretty sure there was another, independent age calculation as well, and they overlapped in their uncertainties(at least until recently)

    Also, I think we can also see things that are further away than the calculated age of the universe, mostly because space itself is expanding, so while the light has only been traveling for 13bln years, the observed location would currently be further than that because the distance has increased while the light was traveling.

  6. 6 hours ago, Arugela said:

    It's for an SSTO design. So, it might be a little odd.

    A SSTO will be out of the usefully dense atmosphere before its condensing equipment could even produce it's own mass in liquid oxygen.

    As such, you will have a lower launch mass by just starting with all the lox you will need.

  7. 7 hours ago, monophonic said:

    You forgot about only 140 protocols that are currently defined in the standards. See https://en.wikipedia.org/wiki/List_of_IP_protocol_numbers for the list. Granted many of those are mainly used by trunk connection providers and others have quite esoteric uses, but UDP is very much used for various purposes.

    Clearly my networks class was a long time ago(IPv6 which is related to #41 on that list only became a draft standard half way through  my Senior year), so I'm glad to hear UDP is finally getting some love.

    Other than TCP, UDP, and IP4/IP6 encapsulation, are you aware of any other protocols currently in use for bulk data transfers?

  8. 35 minutes ago, Piscator said:

    As far as I know, the charges worked immediately. It's just that it took the vessel 40 seconds to sufficiently depressurize to finally loose enough rigidity to be torn apart by aero forces.

    Sounds like we just need a second line of charges then, to allow a pac-man style chunk to be cut loose and allow the depressurization to happen much more quickly.  (or just put it on both sides and cut it in half, which is probably what the FAA would prefer...)

  9. 1 hour ago, DDE said:

    If these are pushed into consumer adoption, would the resulting networks be able to work with the old Internet?

    The internet is designed to be a network of networks, so if the networks are connected to the existing internet and they support  IP(Internet Protocol, mostly handles routing), then they will just be invisibly incorporated.

    If they are not IP compatible(or are preventing from interoperating but are still connected), then some sort of interface node may be required for translating between the incompatible networks.   This may require minor changes(like connecting to IPv6),  it may block all communications that are not white-listed, or the seems might be completely invisible.  It all depends on how they are allowed to interact(if at all).

    If the networks are not connected, then obviously there will be no interactions, but maintaining an air-gap would be very difficult.



    The China article is just about adding an additional protocol in top of IP

    Currently we have UDP(intended for time sensitive broadcasts where missing data is less important than timely data and is never used), and TCP(best-effort protocol that will check for missing bits and re-request them before delivering the intact package to the application, even if the messages are not delivered in the order they were sent, this is the protocol that *everything* is using because losing random parts of your message is generally not considered acceptable).

    At worse, China will configure internal networks to drop all TCP packets and require only using their internal(and presumably easier to control) 'New IP' packets for in-country usage, and we will need to use(presumably state-controlled) translation nodes for swapping between TCP/IP and 'New IP'.

    To outside users it will probably just look like an upgrade to the 'Great Firewall of China'.

  10. Falcon 9 hits Max Q after roughly 70 seconds, this is also shortly after it passes Mock 1

    Wikipedia says the fastest air-breathing  aircraft is the SR-71 blackbird that hit 2,193.2mph/mock 2.81  in 1976

    The falcon 9 first stage only burns for 162 seconds.

    For a first stage air-breathing engine to work, it would, at best, replace less than half of the first stage.  This would cost the use of an extra set of engines, an extra recovery, and lots of extra development.

    I just cannot see a sufficient increase in efficiency during the first minute of flight to warrant splitting up a less than 3 minute burn across 2 stages.

  11. I figured that a chunk of the reason to do the 'hammer toss' would be to transfer additional energy from the booster to starship.

    After release, Super-heavy wants to turn around and slow down, while Starship wants to speed up more, so any sort of momentum transfer should save dV for both.

    Center of mass is probably still inside SH, due to all of the engines at the base, but Starship should have a majority of the remaining weight, so this little maneuver may transfer a significant amount of inertia from one to the other.  Even a few dozen m/s transferred might save tons of fuel, and those would be tons of fuel at stage separation that did not need additional dry-mass.

  12. 1 hour ago, mikegarrison said:

    There can be as many laws against nuclear weapons as  grains of sand on the beach, and it still wouldn't change that if someone used a nuclear weapon to successfully intercede between the Earth and a space rock that was going to hit it, they would not get into any trouble.

    I think you overestimate the rationality of the average activist or dictator.

    They may not actually be able to do anything(depending on the organization that uses the nuke), but they will still raise a ruckus.

  13. 1 hour ago, steve9728 said:

    As the saying, people usually don't have the same feeling of sorrows and joys on one thing. It's like some of the weird episodes of certain romance dramas my gf sometimes shares with me: she thinks it's interesting, but I can't get the logic no matter how I think about it.

    Relationship dramas are very much a Pathos(emotional reasoning) thing.  


    1 hour ago, steve9728 said:

    However, we agreed on the point that the sky-high fireworks couple hours ago were interesting and very Kerbal after she watching I launch one and explode it similarly in KSP.

    A lot of the most impressive parts of Rockets are dependent on Logos(logical reasoning), in part because the sizes and scales do not make a lot of emotional sense.

    (a teaspoon and a 5 gallon bucket are easily recognizable sizes, a 5-kiloton rocket is much more abstract, and for the observers, the explosion took up less of the visual field than your average professional firework mortar, so you need a logical understanding of the scales for it to be appropriately impressive) 

  14. 2 hours ago, Pthigrivi said:

    Just like a stupid question: Why is starship's architecture the way it is? Why not have a superheavy first stage, a reusable second stage, and then a big capsule with a LES and an ablative heatsheild? Like in hindsight the shuttle was an incredibly janky and risky system top to bottom and those heat tiles injected zillions of failure points that risked total loss of vehicle. And now we're doing that again? But now with heat tiles on moving joints and this really risky belly-flop maneuver? And no landing legs that spread out the landing base? We're literally going to drop this thing over a populated area and have it sit down exactly on stage zero and just assume well we tested it 15 or 20 times nothing bad could happen on the 21st. And from top to bottom the plan seems to be that this architecture is gonna work for the moon and even mars, and we're just hauling the airframe around everywhere? It seems like the decision was made to organize it this way basically because Elon liked how Buck Rogers it looked. It had that wow-cool-innovation kinda attitude that gets investors excited. 

    And dont get me wrong. It is cool. Its maybe the coolest thing Ive ever seen. And they're not putting people in it right away, but all indications are eventually thats the plan. Im just wondering if this really high risk tollerance and move-fast break-stuff culture is actually a good idea when it comes to people's lives. 

    As far as I am aware, no one has taken a Launch abort pod version of starship off of the table.

    My understanding is that Elon would prefer to have a starship so reliable that transferring passengers to and from a Dragon capsule for ferrying people to and from the earth would actually increase the total risk of the end-to-end voyage.  Like so much else, this is aspirational until it has been demonstrated as possible.

    My expectation is that the first several 'manned' starships will launch without crew and get a transfer from a Dragon(or possibly SLS) capsule.  (probably for a trip to the moon)

    I also expect Starship to have 100+ flights and probably 50+ consecutive 'norminal' flights before it ever launches with crew on-board, even a version with a LES pod.

    I consider both launching and landing a Starship design similar to the current one with crew(on earth) to be aspirational as opposed to expected.

    And just like other Musk aspirations, they will be great if they can be managed, but that is by no means certain.

    I will be pleasantly surprised if there is never a need for a starship 'shuttle' configuration with a smaller second stage and built-in LES(similar to Dragon) that is only used for transporting several dozen(or perhaps 1-2 hundred) people to and from orbit where it docks with longer-range starships that will actually transport them to the moon/mars/stations outside of LEO.  (replacing the more expensive ticket of using a Dragon capsule for this purpose)

  15. 14 hours ago, Spacescifi said:

    Vacuum translation drive only works in vacuum though.

    Compared to what?

    Interstellar space(1/10 particles per cc) is a vacuum compared to the solar wind, the solar wind(5 particles/cc) is a vacuum compared to the surface of the moon, the surface of the moon(10^4-10^5 particles/cc) is a vacuum compared to Mars, and Mars(0.02 kg/m^3) is a vacuum compared to earth, and earth(1.3kg/m^3) is a vacuum compared to Venus, and Venus(65kg/m^3) is a vacuum compared to Jupiter(25,000 mile deep ocean of liquid metallic hydrogen).

    Can it enter the solar system?  Can it land on the moon? Can it land on Mars?  Can it land on Earth? etc.

    If you are trying to write a story, spending all your time coming up with rules about the universe is a backwards way to do it.

    First you come up with the story, then you identify interesting complications that can be added to the story.  

    Only then are you in a position to do general world-building, and it must be constrained by your story.  (and every question you ask would need to include the relevant story-beat details so helpers know the constraints)

    And frankly, anything that involves startrek-style shuttles is science-fantasy at best.

  16. On 4/13/2023 at 8:35 AM, Shpaget said:

    That's all your reader needs to know about fuel usage in fiction, unless you want to go hard SF, but then forget doing 10 orbital launches without refuelling.

    Only if you want to SSTO from a large body.

    Demios has an escape velocity of only 20kph, letting you both land and launch with only about 12m/s/s of thrust.  This would let a MMU land and liftoff twice before running out of fuel, and any 'real' rocket could probably do a lot more.


    But for earth?  Any realistic rocket using less than 50%  of it's wet-mass as propellant to get to orbit is pure fantasy.  (the real number is probably above 80%, but I am willing to allow for new technologies like rotating detonation engines getting that number lower, just not *that* much lower)  

  17. 1 hour ago, king of nowhere said:

    I made some calculations there. on a probe with 50% of its mass as fuel (a common case, by what I see for some notable missions), replacing hydrazine (Isp 230 s) with LH2/LOx (Isp 440 s) while keeping the same wet mass would increase deltaV as long as the extra mass for refrigeration and insulation is below 35% of the dry mass (or 17% of the mass of the whole probe).

    So, for a probe with 1 ton to orbit and 500 kg of propellant, using cryogenics would be convenient as long as the extra mass for insulation and refrigeration would be no greater than 170 kg. I doubt a small refrigerator and a stirrofoam suitcase could be that massive. so I'd think the issue not the extra mass, but something else.

    possible advantage of hydrazine would be reduced complexity and single point of failures, reliability of cryogenics engines over long missions, and total probe volume. none of them look insurmontable as far as I know, but I'm not enough of an expert to judge.

    To keep things cryogenic you would need larger radiators and a lot more power.  Radiators are more efficient the hotter they are, and it takes more power to move heat from lower temps to higher temps.

    It is not just Styrofoam and a mini-fridge.  

    It also means that any temporary power loss could let your fuel boil off.

    Also, long-term storage of hydrogen is not really a thing as far as I know, between embrittlement and and just seeping through solid materials, hydrogen just does not like to stay in place.

    It might be easier to take up water and just use electrolysis(adding a delay before any burns as the fuel is produced). 

    Hypergolics are also much easier to ignite as they are hypergolic, greatly simplifying the engine, and reducing points of failure.

  18. On 3/29/2023 at 7:27 AM, JoeSchmuckatelli said:

    Even if they are mostly going off of telemetry - data needs inputs.  Engagement (willingness to test) is dropping like a stone 


    On 3/30/2023 at 7:00 PM, uglyduckling81 said:

    Just because 90% of people have stopped playing the game doesn't mean they don't care or their opinion matters less. It just shows how terrible the game actually is.

    Going by Steam telemetry sure, but if you ever used mods in KSP1 you know that you do not play with mods in the steam directory, so anyone playing with mods or otherwise not using the steam launcher will not be in those statistics as an active user.  (and at this point of the dev path, there is a lot of need for mods)

    On 4/3/2023 at 2:45 PM, Alexoff said:

    It is impossible to calculate, I usually launch KSP1 from a shortcut, and not through Steam, so as not to waste time. But many also launch KSP2 like this, not through the launcher. Steam shows at least some specific numbers, but they are not in favor of KSP2.

    I got errors launching through steam, so my 'play-time' is all of 2 minutes back on release day.

    I 'landed' on the Eve seas before the patch and did a mun-minmus tour after the patch.

    (my 'landing' was about as stable as the game-ball at a NBA game, but the vessel was still intact...)

  19. 18 hours ago, Spacescifi said:

    I see. So to save power a more sensible scifi floor gravity plate would be smart. After all people need gravity... nothing else does.

    So gravity plates would only provide gravity within the immediate radius where a person is standing or lying. Meaning if you throw something beyond it would float off till it hit a wall.

    If you only need 'gravity' for people, then just use steel plates on the floor and magnets in your boots.

    Simple, practical, and the energy requirements are low enough that it can be provided by the muscles of the person(mostly for lifting your foot away from the floor)

    You should even be able to tune the strength of the magnets to minimize or eliminate muscle atrophy in the legs(even if the muscles are likely to re-allocate a fair bit over time).  

    This may even act as 'training wheels' for people not accustomed to microgravity for long duration flights on large vessels(like a starship to mars).

  20. Looking at the roadmap, he might be putting a lot of it into the core KSP2 game. 

    It might be more enlightening to ask if he intends to migrate his LS mod, as it sounds like that is less likely to be integrated into the core.

    That said, it may be a while before he has the free time to work on mods, as he is probably putting a lot of extra hours towards his day-job.  I hear they just released a large product in early access and are working hard on supporting it.

  21. 4 hours ago, magnemoe said:

    More of an rant but why are divide by zero that much of an bug in computers. for 8086 cpu's its even an dedicated interrupt. while in 99% of cases there you get x/0 its because its no data getting an average of none attempts and here 0 is a good answer. 
    Yes its nice to capture this but still. 

    "How many groups do you get if you take away zero at a time from your starting set?"  

    Divide by zero is also something of a bug in math, as anything other than 0/0 is nonsensical.  Computers operate on math, so when they try to perform an operation that should produce a nonsensical result, they have a problem because they cannot handle said nonsense.

    Computers are also not able to calculate infinity, and any attempt to do so will also result in problems due to limited computation/storage space. 

    Division of floating point numbers is also the most difficult and time-consuming operation that computers perform, so optimizing those operations, especially pathological cases, can shorten the cycle time of the processor, allowing for an increase in clock speed. (that MHZ or GHZ number that they list for the CPU or GPU)


  22. Steam says I have 2 minutes of play-time and I last played on Feb 24th.

    Why?  Launching through steam does not work for me, so I run it with a short-cut to KSP2_x64.exe in my games folder.


    Remember all the advice about not playing from your steam directory because it will mess-up your mod installs?  I expect that is also having quite a large impact on the steam statistics, even if there is not much in the way of mods just yet.  Old habits die hard


    I can tell you that I have played KSP 2 a lot more than steam thinks I have, even if I am not playing as much as I will once there is some form of progression.


    I suspect that the launcher is having problems because of my multiple monitor set-up(3 monitors with two different sizes), but as the KSP 1 launcher did not work for me either, I just shrugged and created my own short-cut a few minutes after downloading the game.  While I will likely leave a review once KSP 2 is more feature rich, I am not expecting any of my future play-time to be reflected on steam, especially considering how frequently I used mods in KSP 1.


    Edit: I got KSP1 from the squad store, so my only 'KSP' activity on steam shows me downloading KSP 2 and abandoning it in less than 5 minutes.  Not sure how many hours I played KSP1, but my hours played would be at least 4 digits.

  23. On 3/11/2023 at 2:57 AM, Matt_In_Oz said:

    Of course there'll always be the few who will say "aww but you PROMISED..." if the date slips, but they'll complain no matter what happens so ignore them. The vast majority of us understand that the E in ETA means "estimated".

    Perhaps the inevitable slips would go over better if they used a NET Date instead?

    Presumably everyone here would be familiar with the implications of that term as it is used for every future launch date, and those are frequently delayed with few or no recriminations...

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