[HN Gopher] Ion engines could take us to the solar gravitational...
___________________________________________________________________
Ion engines could take us to the solar gravitational lens in less
than 13 years
Author : rbanffy
Score : 49 points
Date : 2024-10-26 18:34 UTC (4 hours ago)
(HTM) web link (phys.org)
(TXT) w3m dump (phys.org)
| rbanffy wrote:
| Spoiler: with a good-enough powerplant that's yet to be built.
| melling wrote:
| "Before this decade is out... "
|
| When Kennedy committed us to go to the moon, the first American
| hadn't even orbited the Earth.
|
| Previous generations just used to get shit done.
| metalman wrote:
| read "failure is not an option"
|
| SPOILER ALERT
|
| lindburg just shows up unanounced at the cape ,security did
| not call ahead just escorted him up to the main deck
| everything stops,he hangs out for a bit,heads on his way and
| then they get back to work
|
| there might not even be a photo,and so you have to trust that
| it happened,and in that is a large part of how shit got
| done,on trust
| Mistletoe wrote:
| > fastaguy88 10 months ago | next [-]
|
| >2.5% of the US GDP ($26 trillion in 2023) would be 600
| billion. At its peak in 1967, the Apollo program budget was 3
| billion, while the US GDP was about 850 billion. So 0.35
| percent. US government spending in 1967 was about 112
| billion, so closer to 2.5 percent of the federal budget, not
| the GDP. Converting to today's 6,000 billion federal budget,
| about 150 billion today, or not quite 20% of the defense
| budget, the largest federal expenditure after Social Security
| (the defense budget is essentially tied with Medicare).
|
| I'm not sure we want those sort of expenses anymore.
| wongarsu wrote:
| Because America was lagging behind the Soviet Union in space
| achievements, and the Soviet Union was parading their
| superior space program to promote Communism.
|
| It's not a generational thing, it's that the Moon landing was
| a top priority Cold War effort to beat the Soviets and show
| that Capitalism is the best. This mission in the other hand
| would be neat but has limited political value. What money
| were are willing to spend on space will mostly be spent on
| having a permanent moon base before the Chinese.
| rbanffy wrote:
| > and show that Capitalism is the best.
|
| Or so it seemed.
|
| > will mostly be spent on having a permanent moon base
| before the Chinese.
|
| At least it could be launched from the Moon with a magnetic
| rail in addition to whatever extra propulsion it could
| carry onboard.
| hagbard_c wrote:
| > Or so it seemed
|
| The term 'capitalism' is often used as a smear by the
| adherents of 'opposing' ideologies like socialism and
| communism so let's agree on a definition using Britannica
| Money's example [1]: _capitalism, economic system,
| dominant in the Western world since the breakup of
| feudalism, in which most means of production are
| privately owned and production is guided and income
| distributed largely through the operation of markets._.
|
| Given this definition and weighing the positives and
| negatives it still seems to be the best system, something
| which I do not see this changing as long as humans remain
| in control of society.
|
| Do you have any examples which show where another system
| has been proven to be superior at a large scale? That -
| scale - is an important factor here since there is a
| direct relation between the scale of the group and the
| applicability of economic systems.
|
| [1] https://www.britannica.com/money/capitalism
| bandyaboot wrote:
| I could be wrong, but these two things don't seem like
| they're really that comparable. Apollo was certainly a
| monumental engineering achievement, but did it require that
| we 100X the state of the art efficiency of some critical
| tech?
| JumpCrisscross wrote:
| > _Apollo was certainly a monumental engineering
| achievement, but did it require that we 100X the state of
| the art efficiency of some critical tech?_
|
| One order of magnitude in propulsion.
|
| When Kennedy made his "We choose to go to the Moon" speech
| [1], our most powerful rocket was the Saturn I. Its H-1
| engines thrusted at 200k lbf [2]. The Saturn V's F-1s did
| 1.5mm lbf [3]. (The Saturn V, similarly, could lift an
| order of magnitude more mass to LEO than the Saturn I.)
|
| It wouldn't surprise me to find 100x increases in some
| material's performance, _et cetera_.
|
| [1]
| https://en.m.wikipedia.org/wiki/We_choose_to_go_to_the_Moon
|
| [2] https://en.m.wikipedia.org/wiki/Rocketdyne_H-1
|
| [3] https://en.m.wikipedia.org/wiki/Rocketdyne_F-1
| bandyaboot wrote:
| So I specifically called out efficiency because 100X'ing
| your thrust is about scaling up technology. That
| generally involves solving engineering problems--figuring
| how to control vibration resonance would be one example
| in the case of the Saturn. 100X'ing efficiency, it seems
| to me, is another animal entirely--it's often about
| legitimate scientific breakthroughs. Like going in, you
| don't even know for sure of its possible.
| JumpCrisscross wrote:
| > _100X'ing efficiency, it seems to me, is another animal
| entirely_
|
| Saturn V had a specific impulse of 263 s [1]. NSTAR did
| 3,000 s [2]. That's an order of magnitude improvement in
| efficiency in 30 years of low-effort improvements.
|
| Starship should demonstrate in-orbit refuelling next
| year. That's another 10x technology. Add on a solar sail
| and you're in the realm of two orders of magnitude of
| efficiency gains with known technologies. (Three from
| Apollo.)
|
| [1] https://en.m.wikipedia.org/wiki/Saturn_V
|
| [2] https://en.m.wikipedia.org/wiki/NASA_Solar_Technology
| _Applic...
| satvikpendem wrote:
| Common philosophical fallacy: just because we are able to do
| things in one stage does not mean we can do things in the
| next.
|
| Of course, I am an optimist, but one cannot relate historical
| circumstances in the same way. I will be glad if it does
| happen of course, but I do not expect it to be so based on
| past performance.
| Gooblebrai wrote:
| I'm genuinely curious. What's the formal name of this
| fallacy? Never heard of it.
| aeonik wrote:
| I think it's just the basic limitations of induction.
| (Inductive fallacy)
|
| Here's a list of them, I'm too tired at the moment to
| figure out which one it is specifically.
|
| https://www.wikipedia.org/wiki/Category:Inductive_fallaci
| es
| satvikpendem wrote:
| The fallacy of faulty generalization:
| https://en.wikipedia.org/wiki/Faulty_generalization
| trueismywork wrote:
| And Mongols conquered almost whole of Asia in less than 100
| years, what's your point?
| throwaway19972 wrote:
| Previous generations also had it easy. Generally speaking
| technological advancement isn't blocked by motivation but by
| other concerns, namely funding.
|
| Personally, I'd rather fix healthcare if we're going to spend
| political capital. https://youtu.be/goh2x_G0ct4 remains as
| relevant as ever
| 77pt77 wrote:
| We'll have the technology in 10 years.
|
| Just like 20 years ago.
| AtlasBarfed wrote:
| So fine, use 1960s general atomics tech and do a pulse nuclear
| drive.
| greesil wrote:
| Simply slap together some antimatter and matter my friend, and
| all your problems are solved.
| marcosdumay wrote:
| Just had to do the calculation.
|
| With 3.5% enriched uranium, about 1/8 of that mass on the power
| supply is fuel.
|
| Yeah, it's not impossible. But nuclear reactors aren't usually
| anywhere near 7 times heavier than their fuel.
| Tuna-Fish wrote:
| I would assume such a high-performance system uses bomb-grade
| material.
| marcosdumay wrote:
| Hum... You can make things about 20 times better by enriching
| the uranium more.
|
| But then you'll get into severe storage and control problems.
| And that thing has to work for 13 years, untouched. There's a
| maximum somewhere on the middle.
|
| Anyway, I don't think reactors on earth are anywhere close to
| 140 times the mass of the fuel either. And they don't have to
| use radiative cooling.
| jandrese wrote:
| Nuclear plants on Earth are way more than 140 times the
| mass of the fuel, but that's mostly concrete for the
| radiation shielding. If you're only worrying about the core
| and cooling infrastructure it's not nearly as bad. But of
| course as everyone has mentioned cooling things in space is
| hard and you'll want to minimize the number of moving parts
| because maintenance is impossible and you can't use
| convection to move heat around which makes it even more
| difficult.
|
| Remember that on Earth nuclear reactors create electricity
| by boiling water to turn turbines. Such a system will be
| far more difficult to design for space.
| perihelions wrote:
| All space nuclear fission reactors use weapons-grade uranium
| --they'd be impractical otherwise.
| nielsbot wrote:
| FTA:
|
| "The paper defined an ideal power plan that can output 1 kW per
| kg of weight.
|
| This is currently well outside the realm of possibility, with the
| best ion thruster power sources coming at something like 10 W per
| kg and even nuclear electric propulsion systems outputting 100 W
| per kg."
| JumpCrisscross wrote:
| 1 kW/kg is an ideal power plant. Does the paper define a
| minimally-viable one?
|
| If we beef up the chemical stage, _e.g._ by launching on
| Starship and re-fuelling in LEO, can we make do with 100 or
| even 10 kW /kg?
|
| (Also, to put 550 AU in perspective, Voyager 1 is 165 AU out
| [1]. At 38,000 mph Voyager 1 [2] travels about 3.6 AU/year [a].
| Going straight out, it would reach the Solar gravitational lens
| in 2131 [b].
|
| [1] https://science.nasa.gov/mission/voyager/where-are-
| voyager-1...
|
| [2] https://en.m.wikipedia.org/wiki/Astronomical_unit
|
| [a] _(38026.77 x 24 x 365) / (9.2956 x 10^7)_
|
| [b] _2024 + (550 - 165) / a_
| perihelions wrote:
| 550 au in 13 years is a mean of 200 km/s--chemical rockets
| are nothing compared to that.
| JumpCrisscross wrote:
| And that is for a flyby.
|
| We're not getting to 550 AU with chemical rockets alone.
| Nuclear, ion and/or solar sails will be needed.
| perihelions wrote:
| - _" ideal power plant that can output 1 kW per kg of weight"_
|
| I wished I remember where I read about this engineering
| problem, because it's an entertaining one. The main constraint
| on your [kW/kg] past a certain point is heat dissipation--the
| mass of the radiators rejecting waste heat into the vacuum of
| space. Thermal radiation scales like [temperature^4] (a very
| fast-growing function), so that parameter's obvious--you have
| to scale your exhaust temperature as high as you can engineer.
| That's how you shrink the radiator size. And you still need to
| run a heat engine--you need a significant temperature gradient,
| _on top of_ the already-high exhaust temperature, to get useful
| work out of it. That 's the temperature output of your primary
| heat source. So, the high-level design solution is: you have an
| array of infrared radiators glowing red, and a nuclear fission
| reactor glowing orange. That's the way to get a high power/mass
| ratio in space.
|
| Also, everything's built around pipes of molten metals of
| different species (optimized heat transport), and the heat
| engine is like a steam turbine that spins on boiling molten
| potassium metal. (I think?) They're really exciting-looking
| machines. I wish someone would build one!
| sxp wrote:
| For those who don't want to watch a video to understand what a
| "solar gravitational lens" is:
| https://en.wikipedia.org/wiki/Solar_gravitational_lens
| m3kw9 wrote:
| Then you have to develop new comms that can travel that far with
| enough bandwith for photos. The lag could be a week or so. Or you
| do relays which is equally difficult in a different way
| credit_guy wrote:
| By far the most realistic engine for deep space travel is the
| Orion project [1]. You load a large rocket with lots of nukes,
| and detonate one at a time behind a pusher plate.
|
| Of course, humanity being what it is, we'll never trust each
| other with the idea of building thousands of nuclear bombs with
| the "firm promise" that they'll only be used for space travel.
|
| [1]
| https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls...
| bibanez wrote:
| This famously appears in the plot of the Three Body Problem
| scifi series by Liu Cixin!
| swasheck wrote:
| didn't work there, either
| jandrese wrote:
| Nuclear explosions release mostly heat and radiation. Are you
| turning your pusher plate into high energy plasma with the
| explosion and using that to propel your spacecraft? My gut
| feeling is that your total ISP for this is disappointing
| compared to the amount of mass you add for the huge store of
| nuclear bombs.
| gorgoiler wrote:
| Idea: achieve massive power provision by transmitting energy from
| a base station to the spacecraft _using space lightning_.
|
| Transmitting power is not a new idea: lasers are the go-to
| example for this. Powering the craft with solar energy is another
| theoretical way of doing it.
|
| My idea on the other hand is different. Imagine spooling a long
| wire behind the space ship and just transmit electricity to it
| the same way you transmit power to your hoover. Except instead of
| sending power up a wire, send it up as bolts of lighting through
| the ionised gas trail your ship is trailing behind it.
| idontwantthis wrote:
| I don't think it leaves behind a trail of ionized gas. The
| positive and negative ions get recombined.
| golol wrote:
| I have my fingers crossed for Starship. If it works as intended
| all these things will happen.
| altharaz wrote:
| There is a very high quality video about how Solar Gravitational
| Lens could be used to map exoplanets, and full explanations about
| the images reconstruction and engineering challenges:
| https://youtu.be/NQFqDKRAROI
___________________________________________________________________
(page generated 2024-10-26 23:02 UTC)