[HN Gopher] NASA's proposed plasma rocket would get us to Mars i...
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NASA's proposed plasma rocket would get us to Mars in 2 months
Author : genman
Score : 69 points
Date : 2024-05-09 19:22 UTC (3 hours ago)
(HTM) web link (gizmodo.com)
(TXT) w3m dump (gizmodo.com)
| devbent wrote:
| > Shorter periods of exposure to space radiation and microgravity
| could help mitigate its effects on the human body.
|
| Of course once astronauts are on mars they will still be exposed
| to radiation, until some sort of shielding can be built.
|
| Which would be an obscene undertaking, and involves moving lots
| of raw and refined materials to mars.
|
| Which means hopefully the price of this rocket to get stuff off
| of earth is dirt cheap, because moving squishy humans to Mars, no
| matter the speed, is not the limiting factor! (Getting humans to
| Mars and keeping them alive there is!)
| sandworm101 wrote:
| >> obscene undertaking, and involves moving lots of raw and
| refined materials to mars.
|
| Or they can dig a hole and/or pile mars dirt on top of their
| living structures. Some materials are better than others at
| absorbing radiation but, as a general rule, mass/depth of the
| protection counts more than composition.
| dyauspitr wrote:
| Building an underground chamber doesn't seem like an impossible
| undertaking. Alternatively, maybe mars already has caves and
| tunnels.
| OnlyMortal wrote:
| There are tunnels that appear to have been created by volcano
| lava. Lava tubes.
| heavyset_go wrote:
| It takes a lot of energy to displace sand/dirt/rocks to build
| anything underground. Human-powered shovels require a lot of
| food and water, and machinery requires combustion and a lot
| of hydrocarbons.
| acchow wrote:
| Submarines run on nuclear. Wouldn't nuclear be the natural
| choice on mars?
| ceejayoz wrote:
| Those are big, and heavy.
| https://www.oregon.gov/energy/safety-
| resiliency/Pages/Naval-...
|
| > The submarine reactor compartments that have been taken
| to Hanford are about 33 feet high and 40 feet in length.
| They weigh between 1,130 and 1,680 tons. Eventually, the
| Navy may deactivate its Ohio class submarines in the same
| manner. Those compartments would be much larger and
| heavier.
|
| Submarines don't have to get them into orbit.
| JumpCrisscross wrote:
| In case you're serious, nobody is suggesting launching a
| water-cooled reactor to Mars. Between the idiot ends of
| the power-source spectrum bounded by, on one end, a U.S.
| Navy PWR and, on the other end, Martian Aramco, we have
| the reasonable options of solar power, batteries, RTGs
| and fission-powered Stirling engines [1][2].
|
| [1] https://www.nasa.gov/directorates/stmd/tech-demo-
| missions-pr...
|
| [2] https://www.nasa.gov/tdm/fission-surface-power/
| ceejayoz wrote:
| I think solar's the far more likely option, yes. Cheap,
| light, low-maintenance. Maybe fuel cells for night.
|
| RTGs aren't gonna power a good-sized base; they're a few
| hundred watts at best.
|
| _edit:_ I very much hope Kilopower pans out.
| jujube3 wrote:
| What is wrong with launching a water-cooled reactor to
| Mars? Or more likely launching the materials needed to
| build it. The active components of a reactor are quite
| tiny -- most of the bulk is in the shielding, which won't
| be necessary on an already radioactive planet like Mars.
| ceejayoz wrote:
| Mars isn't radioactive. A reactor would still need
| shielding.
| JumpCrisscross wrote:
| > _What is wrong with launching a water-cooled reactor to
| Mars?_
|
| Water is heavy and difficult to replace if lost for
| whatever reason.
| Manabu-eo wrote:
| Submarines are encircled by water, that is very good at
| absorbing heat. Nuclear power stations are also
| invariably close to a large source of water.
|
| There is no such thing on Mars, and that significantly
| increases the mass and size of your radiators, making it
| uncompetitive with solar for example, unless the waste
| heat is needed for something else.
| _visgean wrote:
| > machinery requires combustion
|
| solar power / RTGs could power such effort. Digging
| shelters could be done by unmanned missions before the
| manned missions would arrive.
| Alupis wrote:
| I don't think this comment fully appreciates the density
| of hydrocarbon-based energy sources.
|
| No, a RTG-powered bulldozer isn't going to be clearing
| caves and trenches on Mars, ever.
| _visgean wrote:
| rtgs can be used to aid solar in charging batteries, the
| digging process can take a long time, if you space it
| correctly you would be able to get that energy from solar
| etc
| Alupis wrote:
| No, you cannot. You are still dramatically
| underestimating the density of hydrocarbon energy. Solar,
| electric, batteries, etc do not even remotely come close.
|
| This line of thinking also dramatically underestimates
| the energy requirement to excavate dirt and rock...
|
| Then, figure it's on another planet with dust storms that
| have already killed solar-powered rovers, etc.
| _visgean wrote:
| > You are still dramatically underestimating the density
| of hydrocarbon energy. Solar, electric, batteries, etc do
| not even remotely come close.
|
| I never mentioned hydrocarbon energy. You keep bringing
| it up for some reason.
|
| > Solar, electric, batteries, etc do not even remotely
| come close.
|
| I don't need them to come close. I need them to do the
| job, and they do it
|
| > This line of thinking also dramatically underestimates
| the energy requirement to excavate dirt and rock...
|
| here are some electric, battery powered excavators:
|
| - https://www.volvoce.com/europe/en/products/electric-
| machines...
|
| - https://www.wackerneuson.cz/en/zero-emission/electric-
| excava...
|
| - https://www.komatsu.jp/en/newsroom/2023/20230721
|
| - https://www.jcb.com/en-us/products/compact-
| excavators/19c-1e
|
| - https://www.bobcat.com/na/en/equipment/excavators/compa
| ct-ex...
|
| - https://www.volvoce.com/europe/en/products/electric-
| machines...
|
| - https://www.hitachicm.com/eu/en/onsite/article/Introduc
| tion_...
|
| - https://www.casece.com/en/europe/products/excavators/d-
| serie...
|
| - https://www.kubota.com/news/2023/20231218.html
|
| There are excavators both small and big so yes you can
| definetely excavate using electricity alone.
|
| > dust storms that have already killed solar-powered
| rovers
|
| Looking at list here
| https://en.wikipedia.org/wiki/Mars_rover I guess you talk
| about Zhurong and Opportunity? Both of these seems like
| success story given that they survived way longer than
| they were expected to..
| toxic72 wrote:
| Just wanted to add to your list, electric dozers have
| been on the market for some time. Even more impressive
| given the weight.
|
| https://www.cat.com/en_US/products/new/equipment/dozers/m
| edi...
| Alupis wrote:
| And how do we get a 51,333 lb bulldozer to Mars?
|
| Not to mention this bulldozer _still burns hydrocarbons_.
| It uses electric drive for it 's tracks - and the
| electricity is generated by hydrocarbons!
| bryanlarsen wrote:
| a gallon of gas produces about 33 kWh. A meter of solar
| panels (which has a similar weight without glass)
| produces about 1000 kWh / year. (It's about the same on
| Earth and Mars since a Mars year is almost twice as long)
| Alupis wrote:
| This isn't a helpful metric though - even if we had a
| vast grid of solar on Mars - how is the power going to be
| stored? Batteries? How do you get them there? Who plugs
| it all in? Who maintains if when it fails?
|
| Excavating earth and rock in the volume being proposed
| (to build underground dwelling spaces) is not trivial...
| bryanlarsen wrote:
| Why store it? Dig when the sun is shining and idle when
| it isn't.
|
| Your other concerns are power source agnostic.
| Alupis wrote:
| All of the other issues still exist. How do you setup a
| solar farm on a remote planet without any humans being
| involved (the OP was discussing tunneling before any
| humans arrived). Who plugs it all in? Who dusts it off
| after a storm? How long are the cables that power this
| excavator? What happens if they get tangled or damaged?
|
| It's just a non-starter of an idea...
| arrosenberg wrote:
| Seems like a use-case for a "controlled" thermonuclear
| demolition project.
| ortusdux wrote:
| I still think that this would explain Musk's dalliance with
| tunnel boring machines.
| malfist wrote:
| The easiest solution is to set up shop in a cooled volcano tube
| dmurray wrote:
| Most of the materials could surely be found on Mars. A shelter
| built out of sandbags would be a low tech solution that would
| get you a large part of the way there.
|
| Further, Mars itself shields you from half the radiation (at
| night), the Martian atmosphere shields you from a little more,
| and Mars is further away from the Sun on average than an Earth-
| Mars spaceship.
|
| Radiation during transit really does seem like a bigger issue.
| pmontra wrote:
| There are also cosmic rays. They come from every direction,
| so even at night.
|
| An experiment measured that kind of radiation about 20 years
| ago https://en.wikipedia.org/wiki/Mars_Radiation_Environment_
| Exp...
| dmurray wrote:
| The planet still shields you from half of those.
| lupusreal wrote:
| It's not an intractable problem, just send a robot bulldozer
| and excavator a few years beforehand. The real problem with a
| Mars colony is the economics for making it anything more than a
| small scientific outpost / political stunt. Forget the upfront
| cost of the habitat/etc, how do you actually create a self
| sustaining Martian economy? I've never heard a realistic answer
| for this.
| mongol wrote:
| It is an interesting problem of energy. How would a robot
| bulldozer or excavator be powered? They require more power
| than a rower.
| lupusreal wrote:
| They don't require more than a rover if you accept them
| doing their work far slower than their normal earth
| equivalents. Hence sending them years in advance to dig out
| a some holes that would only take a few days for excavators
| on Earth.
| tsimionescu wrote:
| While speed is a factor as well, you still need a lot
| more energy consumption to move a mass of rock&dust some
| distance away than to move a small rover. This
| immediately follows from the formula for work and the
| gravitational force.
| lupusreal wrote:
| Given enough time, you can dig out a house foundation
| with a spoon, power is not an issue here. The less power
| you have available the slower you work. If your robots
| wear out, you send more.
|
| The real problem is finding enough time and money to
| waste on such a fruitless endeavor. If that can't be
| managed it nullifies the entire problem of digging a hole
| on Mars since a Mars base is nothing but a waste of time
| and money. Wasting time and money is table stakes.
| myblake wrote:
| Solar still works on Mars as does fission. Plenty of stuff
| about this online if you look.
| tsimionescu wrote:
| Sure, but solar is not great for digging underground. So
| now you need a solar station and wires connected to it,
| and that already complicates things significantly and
| massively increases the chance of failure.
| pie420 wrote:
| small nuclear power plant would be the first thing sent to
| mars, or many arrays of solar cells. then pods of
| batteries, then construction materials, then equipment,
| then humans.
|
| realistically, the assembly could be done remotely, and you
| would want at least two habitable shielded pods with a very
| large excess of food/oxygen/supplies stored by the time
| humans arrived.
|
| This might seem impossible, but i don't think it's
| particularly difficult, the only major hurdle would be the
| budget. The rocket vessel will make a good living pod, the
| small nuclear reactor was studied by the US Gov in the 50s,
| so that shouldn't be a problem, except maybe cooling, but
| again that should be a solvable problem.
| rendall wrote:
| > _how do you actually create a self sustaining Martian
| economy? I 've never heard a realistic answer for this._
|
| What would a realistic answer even look like? I imagine that
| since nothing like jump-starting an economy _ex nihilo_ on a
| cold, desert planet has been done before, any proposal at all
| would sound wildly unrealistic.
| verve_rat wrote:
| Tourism? That's the only thing that even approaches
| realistic that I can think of.
| skissane wrote:
| The problem with the Martian tourism is the huge amount
| of time it takes - around 3 year round trip with current
| conventional rockets; this proposed nuclear rocket would
| cut travel time to 2 months one way, but you are still
| looking at a 4 month minimum just in travel time. A
| billionaire who could afford a Martian vacation would
| likely struggle to take the time out of their schedule
| for one. This is why I think lunar tourism is much more
| viable: a vacation on the Moon need only take 2 weeks (a
| week of travel time and a week there; and nuclear
| propulsion could cut the travel time substantially)
| lupusreal wrote:
| _" The Mars colony would produce [service/good] to generate
| income sufficient to pay for the colony's upkeep /
| expansion."_
|
| Let's assume the colony itself is built by some idealist
| willing a trillion dollars to the project or something. Now
| that you have a base on Mars, how do the inhabitants pay to
| keep it going? Self sufficiency is too far fetched at this
| stage so they need regular supply shipments from Earth, so
| they need income of Earth currency.
| skissane wrote:
| > Now that you have a base on Mars, how do the
| inhabitants pay to keep it going? Self sufficiency is too
| far fetched at this stage so they need regular supply
| shipments from Earth, so they need income of Earth
| currency.
|
| Emotional blackmail: "If Congress doesn't pass the
| Martian colony funding bill, Americans on Mars will die"
|
| National competition: "China's Mars colony is bigger than
| ours"
| kallistisoft wrote:
| As far as I know the plan has always been to use the martian
| regolith and water as primary radiation shielding -- same as
| the moon.
|
| Here is a recent (2022) paper[1] on the concept, but you can
| easily find scholarly work on this going back many decades...
|
| [1]
| https://www.sciencedirect.com/science/article/abs/pii/S00320...
| ceejayoz wrote:
| https://en.wikipedia.org/wiki/Martian_lava_tube have also
| been proposed as pre-existing possible shelters.
|
| https://en.wikipedia.org/wiki/Caves_of_Mars_Project#/media/F.
| .. "HiRISE image of Mars hole 'Jeanne', about 150 meters (492
| feet) across and at least 178 meters (584 feet) deep."
| phkahler wrote:
| >> Of course once astronauts are on mars they will still be
| exposed to radiation, until some sort of shielding can be
| built.
|
| Send tunnel boring machines. There a company making electric
| ones.
| TheDudeMan wrote:
| "hopefully the price of this rocket to get stuff off of earth
| is dirt cheap"
|
| This is not a launch technology.
| JumpCrisscross wrote:
| Not with that attitude!
| JumpCrisscross wrote:
| Zubrin gave a great talk in 2011 on VASIMR, another drawing-board
| nuclear magneto-plasma propulsion technology [1]. It's not only
| untested and unnecessary, but gets used by opponents of space
| exploration as a convenient reason to delay funding until the
| magic kit is ready.
|
| [1] https://www.youtube.com/watch?v=myYs4DCCZts
| perihelions wrote:
| I love the idea of nuclear fission space propulsion. But, this
| concept doesn't look even mildly realistic. The first fission-
| electric rocket in space isn't going be f'ing 10 gigawatts [0]:
| it's going to be 5-6 orders of magnitude smaller, it's going to
| be conservatively designed and cautiously iterated, in a way that
| gets useful engineering data even if it doesn't work the first
| time (it won't). This craziness is an Nth-of-a-kind iteration you
| might consider attempting, >20 years* after your 1st success,
| after >20 years of sustained development effort. It's not a near-
| future plausibility.
|
| *(Coincidentally, the first serious project was cancelled about
| 20 years before the present day [1]. That would have been an
| interesting alternate history...)
|
| [0] https://www.howeindustries.net/ppr
|
| [1] https://en.wikipedia.org/wiki/Jupiter_Icy_Moons_Orbiter
|
| edit: To explain my reasoning a little: 10 gigawatts is gigantic
| amount of violently destructive energy--thermal energy, radiation
| energy, mechanical and vibrational [2] energy--you're trying to
| squeeze into a _lightweight, complex, mass-optimized aerospace
| device_ that needs to run unattended and without maintenance for
| many years, without failing. That 's probably very hard to get
| right. There have been many nuclear electric reactors in space
| already, but remarkably none of them, in operation, had any
| moving parts! They were all solid-state thermoelectric
| converters. I believe the bulk of that design choice boils down
| to "it's simple and conservative". Thermoelectrics aren't
| impressive by any other metric--just simplicity.
|
| Even the first, smallest nuclear electric turbine in space will
| be a majorly impressive achievement, for whoever succeeds at it.
|
| [2] Let's not forget:
| https://en.wikipedia.org/wiki/Galileo_project#High_gain_ante...
| akira2501 wrote:
| The distance between Mars and Earth is not fixed and is on a
| multi year repeating cycle.
|
| So, do they mean 2 months at the minimum distance, or the
| maximum?
| JumpCrisscross wrote:
| > _do they mean 2 months at the minimum distance, or the
| maximum_
|
| This is a high delta-v vehicle, so anything on the outside of
| the porkchop [1].
|
| [1] https://en.wikipedia.org/wiki/Porkchop_plot
| akira2501 wrote:
| I'm not understanding how that plot applies here or how it
| answers the question.
| perihelions wrote:
| The orbital timing makes little difference, because the
| velocities involved are significantly faster than planetary
| orbital speeds. Longer distances will take longer times,
| but not _proportionally_ longer: the limiting factor is the
| acceleration and deceleration.
|
| The diagram the parent linked is the conventional
| presentation for how to relate orbital transfer times with
| orbital phases--conventions that _do not apply_ to high-Isp
| transfers, such as this concept. Orbital phases are _not_
| important here.
| akira2501 wrote:
| > orbital transfer times with orbital phases--conventions
| that do not apply to high-Isp transfers
|
| The minimum distance to Mars is 33.9 million miles. The
| maximum distance to Mars is 225 million miles. You're
| telling me this engine is so powerful it doesn't matter
| when you launch you'll always get there in 2 months?
|
| Isn't Mars occasionally on the other side of the Sun from
| us? I'm still failing to grasp this.
| JumpCrisscross wrote:
| > _minimum distance to Mars is 33.9 million miles. The
| maximum distance to Mars is 225 million miles_
|
| Two identical spacecraft could travel the same distance
| between Earth and Mars and arrive at wildly different
| times. You're never taking a linear path; it's like
| talking about the diameter of the Earth when comparing
| two steamboats.
| akira2501 wrote:
| > Two identical spacecraft could travel the same distance
| between Earth and Mars and arrive at wildly different
| times.
|
| Okay, but this is one spacecraft with a single stated
| time.
|
| So, does that mean it takes the same time regardless of
| when it was launched in the cycle? Or, does the two month
| figure only apply to launches at or near the minimum
| distance?
| JumpCrisscross wrote:
| The distance you're referencing doesn't matter. You're
| never travelling the straight-line path the distance
| measures.
| perihelions wrote:
| - _" The minimum distance to Mars is 33.9 million miles"_
|
| The path we're talking about is not this straight-line
| distance; it's a much longer trajectory that looks closer
| to this [0] (probably longer than the one in this
| particular diagram). Part of the reason is vector
| velocity addition with Earth's orbital velocity; part of
| it is that the electric acceleration phase is not
| instantaneous--rather it's very, very slow.
|
| [0] https://www.researchgate.net/figure/Mars-transfer-
| trajectory...
| shagie wrote:
| The _current_ orbital limitations can be found with a
| neat tool - the NASA Trajectory Browser.
|
| https://trajbrowser.arc.nasa.gov/traj_browser.php?maxMag=
| 25&...
|
| The "View" and play on any of those is neat. Well, Earth
| - Mars isn't as neat as some other routes. I can't recall
| the exact settings, but I've dabbled with it in the past
| and had some EVEJ routes (Earth to Venus to Earth to
| Jupiter)
| Keyframe wrote:
| It literally does. GP used (high) delta-v as a measure
| which correlates energy and change in velocity (which
| proposed propulsion is about) and porkchop shows it's not
| how as simple as how far/near source and destinations are,
| hence its existence and use.
| pmayrgundter wrote:
| Good.
|
| But it's only a few days with a million ISP from fusion.. let's
| raise the bar ;)
| trhway wrote:
| my napkin gets almost the same with existing and relatively
| simple tech - solar or nuclear source of energy powering ionic
| drive (as the one already made and tested/flown by NASA with 3500
| Isp (vs. yet to be made 5000 mentioned in the article)). Solar
| can actually beat nuclear if it is made as very thin, ie. light,
| film. I think and hope that SpaceX would end up using solar+ionic
| combo instead of chemical for Mars (and nuclear + ionic for
| beyond Mars).
| ChrisMarshallNY wrote:
| The AppleTV+ alternate history show, _For All Mankind_ , works on
| the theory that we got the NERVA engine working.
|
| According to that show, we should have been on Mars for the last
| twenty years.
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