Terwin
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Posts posted by Terwin
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Hydrogen leaks. Through anything. While doing so, Hydrogen also make the things it leaks through more brittle.
Leaking that hydrogen into a LOX tank seems like a good way to get a big explosion.
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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.
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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.
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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)
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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)
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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.
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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)
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19 hours ago, Calvin Kerman said:
Is there any way to specify the placement of WOLF's abstract resources by body, or is it completely random?
The placement is random, but once you have surveyed a biome, you can edit the resources remaining in a specific biome in your save file.
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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.
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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...)
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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).
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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.
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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)
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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.
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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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17 minutes ago, JoeSchmuckatelli said:
The question is how many other people are going to be willing to open their wallets given 'the word on the street?' (and if they are... when?)
Isn't that sort of the reason they set out the major features and the order in which they plan to implement them?
'These features are not yet present, but we plan to add them, if you deem one or more of them to be required before you want to buy the game, then just wait and buy it when those features have been added, and continue to enjoy KSP1 until then.'
It just turns out that there are some less major mile-stones that are also needed for some players, but no one was aware of them in a time-frame to do anything about it.
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8 hours ago, Faile said:
Keybindings seem to bleed through sometimes, not always.. next I'll test if it happens when launching KSP via steam or just when launching from bypass shortcut
Yea, looks like if you launch via steam and the launcher, you place a command pod, select the name of the ship ( fly safe ) and press M to start typing Moonraker for example -> boom, you're in the tracking station
Note: this doesn't happen if you've launched KSP2 from the direct application shortcut many of us have on our desktops or start menus so I'm assuming this is an issue with user privilege inheritance and keybinds.
Same thing happens when trying to 'del' a part you have selected, you get told flight controls have been switched to and from docking controls ( del keybind while in flight )
Ah, that explains why I have not seen this issue, I was not able to launch using the launcher, I had to go to the KSP2 directory and run KSP2_x64.exe directly to get it to start.
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I'm excited for stock interstellar colonies that can launch their own ships.
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37 minutes ago, darthgently said:
There is a non-zero chance that if one falls asleep without being properly stowed one could wake up stranded.
Every human in space comes equipped with a pair of bellows attached to an adjustable nozzle and a pair of paddles.
So if needs be you could 'swim' or 'blow' your way towards a hand-hold. Not that it would be fast, but it would work.
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23 hours ago, sevenperforce said:
A fuel-switching tripropellant engine is attractive because it can start with high thrust and lower specific impulse in a sea-level nozzle, then switch to lower thrust and higher specific impulse, using the same nozzle as a vacuum nozzle. Basically an altitude-compensating engine (as opposed to an altitude-compensating nozzle). If you wanted to build a reusable spaceplane, you could use this kind of engine and have it launch vertically with a couple of fairly modest strap-on boosters, and it would be able to have both high TWR at liftoff and high specific impulse at orbital insertion.
The down-side of needing a combustion chamber that can handle properly mixing and expelling both combinations seems highly problematic.
Even with a normal engine, you have space issues putting all the injectors you want where you want them, so having two sets would be very difficult(not to mention the space for piping), then you need the throat to be properly tuned to both sets of combustion, which seems unlikely to be an easy thing to manage, as well as putting substantial constraints on the relative fuel flow between the two reaction types(volume, temperature and pressure capabilities of the combustion chamber and throat will not change between fuels after all, and this may reduce isp to the point of making it worthless for many/most combinations)
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1 hour ago, Gargamel said:
But what if we are the last?
Counting from the formation of the earth to when the sun expands to engulf the current earth orbit, we are less than half way along.
To ensure that no life will evolve after a sterilizing event before the end of this epoch, would likely require the earth no longer be a planet in the goldilocks zone.(or any other 'zone' that turns out it can support the development of life)
As such, hopefully we will have enough time to become multi-planetary before whatever comes and either turns the earth into an asteroid field or changes the orbit enough that it an never again sustain life.
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8 hours ago, Shpaget said:
The only reason it is loose and all wobbly is to increase accuracy.
If you hook the loose bit over the end, it should pull taught and thus extend the hook-part past the end of the tape, if you butt it up against an edge, it should push in so that the measured end is still accurate on the tape measure.
Personally, I usually start measuring at the 6 or 12 inch point on the tape and subtract that from the end point when feasible, because the loose bit also bothers me...
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As far as I can tell, the StarWars universe has anti-gravity tech that is pretty ubiquitous and used in everything from wheel-barrows to starships, with no real energy requirements.
I do not believe that any StarWars vessels actually get up to orbital velocities, and just sit there on anti-grav instead. (this is why they can 'fall out of orbit' if they get too damaged, and also why a bomber can drop bombs on them from above)
Hyperspace probably involves some sort of Albercurrie drive using the same tech. The 'engines' at the back are more akin to fairy-dust vents than actual engines, and may only be relevant for hyperspace.( perhaps venting something that helps prepare the area for hyperspace?)
If you give me that magical anti-grav tech, I could get you a family-car sized vehicle that can SSTO to the moon and back, possibly using a compressed-gas thruster to ease the transition between the earth-dominated and moon-dominated gravitational domains.
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If you have arbitrary amounts of power available, then this should be indistinguishable from an ion thruster(assuming that your magnetic thruster works at all).
I do not think that an ion thruster requires a particularly large exhaust area per unit of thrust, just large amounts of power(a sizeable chunk of which is used for stripping electrons off of the reaction mass to turn it into ions which you can push with electromagnetism)
As current ion engines have ISPs in the 2000-5000s range, that should be adequate for SSTO if you have arbitrary amounts of energy available without needing arbitrary amounts of weight to generate it.
With 5K isp and >1g thrust, you should be able to get to earth orbit with only a ~20% fuel fraction(I think)
So even if ~30% of your vessel is dry-weight(power/structure/engines), you could get 100t of cargo to orbit with a ~200t launch weight using a 5000s isp engine with sufficient thrust.
The current problem with high-isp engines are the thrust-to-power ratio where you need at minimum of ~50kw per newton of thrust for a 100% efficient 10,000s isp engine, or ~25kw per newton of thrust for a 5000s isp engine.
This means ~50w per gram at 10,000s or ~25w per gram at 5,000s to accelerate at 1m/s/s, so you would need at least 10 times that for launch.
This means 500kw/s or 250 kw/s for each kg of launch weight.
The SSTO above would require >50gw/s from a mass of less than 600kg(which also includes the engines and structure) for long enough to get to orbit(for more than 8 minutes), requiring an energy density of more than 40 giga-joules/kg.
This is roughly 300 times the fuel density of hydrogen(not counting the weight of oxygen, I think) or only about 1/2000th the energy density of uranium. Clearly this would need a nuclear reaction to produce the power, but would require a 50gw nuclear plant at a mass of perhaps half a ton.(not something we can manage today, and would need massive heat-ejection capability)
SpaceX Discussion Thread
in Science & Spaceflight
Posted
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.