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#101 Re: Interplanetary transportation » Interplanetary Sailing Using Laser Beams Luna Phobos » 2021-03-31 14:15:58
For Quaoar re #12
Your suggestion for the Moon is interesting and it seems to me worthy of further development. By any chance, could you make even a crude, hand drawn sketch of your idea. If you can create an image of the sketch, you can upload it to imgur.com, and Right click on the image to secure a link for BBCODE, which you can paste in the forum. To see examples of such images, you can find them in the writings of RobertDyck and Void. Void in particular has demonstrated mastery of computer drawing tools, but a hand drawn sketch would be fine!
(th)
The ship in this image is the mini-mag orion a miniaturized version of Orion drive, which uses small fission pellets that reach critical mass after being imploded with a Z-pinch.
My ship is quite similar to her, but she has three differences:
1) there is not the heavy Marx generators for the Z-pinch, so she's lighter.
2) the pellets are not made of uranium (or other fissile material) but inert pressed regolith, because energy comes from an external source.
3) the magnetic nozzle coils are not an empty cage like in the posted design, but surround an hemispherical tungsten or molybdenum mirror, which focus the laser beam on the pellets.
#102 Re: Interplanetary transportation » Interplanetary Sailing Using Laser Beams Luna Phobos » 2021-03-31 12:44:13
For Quaoar re #10
Thank you for this interesting addition to the topic!
While your post seemed to be Earth-centric, I immediately connected with the problem of launch from the Moon. A while ago, Calliban led a discussion of the benefits of various kinds of launch from the Moon. One of those sprang from a post of Void, who was thinking about steam as a propellant.
The issue not solved at that time was how to deliver power to a vehicle so that onboard water could be converted to steam for propulsion.
Your post might be a springboard for renewed contemplation of this topic.
At the time of the original series, I was imagining power might be supplied to the vehicle by trackside sources.
Your post (for some reason) suggested a solution that may well be less expensive and more practical ...
A laser AFT of the vehicle could direct energy toward the vehicle, where mirrors (of suitable capability) would direct the energy to a boiler (of suitable design) able to deliver high energy steam to propel the vehicle along a track to Lunar escape velocity.
Working from memory (the original posts are safely stored in the archive) my recollection is that an acceleration of 2 ( or 3 ? ) along a track of 70 ? miles would deliver a vehicle to escape velocity.
I hope that someone (perhaps not yet a member of the forum) will read this sequence, starting with your post, and decide to explore the practicality of this idea.
Such a launch method would have many advantages over all (ALL) the alternatives.
(th)
I'm not Earth-centric but superearth-centric , because in my next novel I need to find a way that an alien civilization would reach the orbit of their planet, which has a mass of 5.1 earth masses, a radius of 1.6 earth radii, a surface gravity of 2 g and an orbital velocity of 14.14 km/s. With a rocket it seems prohibitive, so I shifted to laser propulsion which seems feasible.
An other interesting fact of this planet is that the atmosphere is very dense, almost 6.5 kg/m3, so flying is very easy despite the gravity and even very heavy creature can do it.
For the Moon I suggest a laser ablative propulsion with a parabolic metallic reflective nozzle surrounded by superconductive coils and an ammonia gas drive machine (similar to that of Orion Drive) which expels pellets made of pressed regolith. When the pellets reach the focus of the mirror, they are vaporized and ionized by two laser pulses. Then the plasma is reflected by the magnetic field of the coils generating thrust.
This system uses solar energy from panels to power the laser arrays and regolith as propellant which is very abundant on the moon soil.
#103 Interplanetary transportation » Sodramjet: the Mach 16 chinese scramjet » 2021-03-31 03:39:44
- Quaoar
- Replies: 5
I have found this article
https://www.sciencedirect.com/science/a … 6120305227
about a new chinese scramjet able to reach Mach 16 (almost 5.5 km/s).
If it works it will be very useful to build a SSTO.
#104 Re: Interplanetary transportation » Interplanetary Sailing Using Laser Beams Luna Phobos » 2021-03-31 03:30:31
Another interesting possibility is to use laser arrays to reach the low orbit from the surface: there are two possibilities
1) air-breathing laser pulse detonation engine, like the lightcraft of Leik Myrabo (https://en.wikipedia.org/wiki/Lightcraft)
2) laser ablative propulsion, where the laser comes from an external array while the propellant is stored on the spaceship
I don't know if it is possible to reach orbital velocity on high Earth atmosphere only with the first, but a combination of both might work. Airbreathing up to 3500 m/s then laser ablative propulsion outside the atmosphere
#105 Re: Terraformation » Is terraforming Mars impossible? Maybe not... » 2021-03-30 15:48:25
Terraforming Mars, if it's possible, would require thousand years. But before starting it we need to know if there's life or not. If there is life, I think it's wrong to disrupt an ecosystem. It would be better to leave Mars as it is and build orbital O'Neal's cylinder, which would have the right atmosphere and the right gravity for humans.
#106 Science, Technology, and Astronomy » Hydrogenic photosynthesis for superearths » 2021-03-25 14:42:10
- Quaoar
- Replies: 1
I found this original work about the possibility of life in a superearth so massive to retain its hydrogen envelope:
https://www.mdpi.com/2075-1729/4/4/716/htm
Hydrogen superearths are rocky planets up to 10 Earth masses with liquid water oceans, continents but have an atmosphere mostly composed by hydrogen rather than nitrogen.
It's very interesting to note that synthesizing carbohydrates from methane and light requires less energy than doing the same thing from CO2 and light, like plants do on our Earth. So hydrogen superearths have a habitable more wide than nitrogen-oxygen planets, and hydrogen photosynthesis can work well even in infrared band with wavelength up to 1.5 micron.
#107 Re: Interplanetary transportation » Space Launch System » 2021-03-23 11:58:33
Oldfart1939 wrote:I maybe the only person here to even raise the topic of sexual activity. That needs to be considered as well. I don't think we'll be sending a group of Monks on these long, deep space journeys?
NASA had the attitude there must be no sex in space. But Europe has the attitude that consenting adults can do whatever they want on their off time. Europe was quite insistent on this point, so there is no prohibition re sex on ISS. That same principle will have to hold on Mars.
A Mars mission would last almost three years, so it's better to embark couples from the beginning of the mission.
#108 Re: Human missions » Mini magnetosphere radiation shielding for a manned mission » 2021-03-18 10:34:33
For Quaoar .... here is where your transition to creating drawings as Void has done would be helpful.
You can (if so inspired) create drawings that can be stored at imgur.com. Imgur.com is helpful to provide a link to the image that you just paste into a message here. The option to look for is "bbcode". You will find it listed as an option after you store your image. I can never remember if it is right or left click, to reveal the link menu, but it is one or the other. Simply click on the bbcode choice and it will be saved to your computer's temporary memory (clipboard).
Log into NewMars forum, create a new post, and paste the link into the new post. Voila! Your image of a baton shaped space vessel will appear for all to see.
(th)
That's the Ruth Bamford's design: in the middle there's an extendable truss with a superconductive coil.
#109 Re: Human missions » Six-legged freaks - can the Starship land on those legs? » 2021-03-18 09:55:36
I expect the TAF factor cuts both ways - it allows them to adopt fresh approaches to long standing issues that sometimes work better (and a lot cheaper). That's the sort of approach that allowed Tesla to get a lead in EVs - they didn't just bolt on batteries to an existing vehicle model.
On the subject of legs, I was wondering about a supplementary stability set up. So you keep the stubby legs but at the bottom of the rocket you have three or maybe five extendors that follow the rounded contours of the rocket (so not like the Falcon 9 with its fold down legs going up the rocket body). As the rocket lands, these extendors, connected to the rocket body by hinges move out from the rocket body and stabilise the rocket on landing. With a circumference of over 28 metres to play with 5 of these curved legs could each be 5 metres in length. But that might be too much. I'm thinking (intuitively and probably wrongly!) perhaps 3 metres would place less strain on the hinge. Just another thought as well - if they were on springs and held back mechanically, leg deployment might used far less energy - just a case of moving 5 bolts out of place. There might need to be mechanism to lower the legs slightly so they make good contact with the ground.
You might be able to fire all the bolts with pyrotechnics which I understand have proven to be a very reliable technology in rocketry over the years, to effect mechanical movements.
Probably, now it's too late to change the design, but wouldn't it better to build a belly-lander with main rockets on the tail, landing/take
-off rockets on the belly, plus four landing legs?
A belly-lander is much more stable and would be a more practical surface habitat for the astronauts, who don't need to take a complex elevator every time they return from an exploration, but a simple ramp with steps.
#110 Re: Human missions » Six-legged freaks - can the Starship land on those legs? » 2021-03-18 09:44:01
Quaoar:
The answer to your question is "they themselves have not done it before". Most organizations refuse to learn from prior experiences of other organizations, especially those outside their very restricted experience base and engineering discipline. It is often a fatal mistake.
Spacex got caught by that lack once before, when they first started flying Falcon-1. It nearly bankrupted them before they got it right. What they knew well was liquid rocket engines, that being the Merlin kerolox engine still used in Falcon-9 and Falcon-Heavy. What they did NOT know (that they didn't know) was anything about the flying of staged supersonic vehicles.
That lack caused 3 collisional failures due to the drafting effect, which is quite strong in supersonic flight, despite the thin air at staging altitudes. They got it right on the 4th flight, which averted bankruptcy. And they have gotten that part right ever since. But that is NOT the only thing that they know little-to-nothing about.
What they don't yet know that they don't know is what it takes to be stable against easy tip-over from statics 101, and also what it takes for soft dirt to support a heavy object, which actually comes from civil engineering foundation design, nothing to do with aerospace. The reason they don't yet know about these things is that they have never landed anything, on anything but a flat reinforced concrete pad or a flat steel deck.
It is precisely a "technical arrogance factor" that prevents them from learning the already-known lessons about static stability and soil bearing strength from the experiences of others. They are not alone in that technical arrogance factor, which is fundamentally also a technical ignorance factor. Most big organizations suffer from it. (Including outfits like NASA that ought to know better.)
GW
In the junior-high school we have studied that a body fells down when the center of gravity goes outside the base area. That's elementary static, how it is possible that an engineer doesn't know what even school children know?
#111 Re: Unmanned probes » Mars glacier mission to search bacteria » 2021-03-17 15:42:58
For Louis re #2 ...
For Quaoar ... May I invite your consideration of asking Japan for help?
(th)
Sure.
#112 Re: Human missions » Mini magnetosphere radiation shielding for a manned mission » 2021-03-17 15:36:41
Robert:
Why could not your magnetosphere poles be aligned with one particular diameter of your ring, and just rotate with it? I know very little about EM physics, so I do not understand why the magnetic field cannot be rotating. You would still have to have shielding near those poles.
But I'd hazard the guess there would be less leakage of radiation into the magnetic field, simply because the "openings" are moving targets.
Sorry, just my ignorance showing.
GW
The design of the ship proposed is similar to your rigid baton, with the superconductive coil in the middle and the habitat at one end. So the habitat is far from the magnetic poles, where there is no shielding, and is completely protected even when the ship spins for artificial gravity, with the rotation axis perpendicular to the orbit.
#113 Re: Human missions » Six-legged freaks - can the Starship land on those legs? » 2021-03-17 15:28:49
Then we're back to legs. Landing on Mars with soft uneven ground, Starship will need legs like Falcon 9. Landing on Earth on a concrete pad, it can made do with smaller legs, but they will need some sort of shock absorber. At first I thought those legs were simply a solid piece of metal made of sheet metal. If they can telescope somewhat, then I don't think it's enough. Shock of a vehicle that heavy hitting a concrete pad will cause damage to the thin stainless steel tank. Especially when the tank is practically empty. Wouldn't that shock cause metal fatigue? I'm no expert re metal fatigue, but this vehicle is intended for multiple flights. I would expect legs that work like struts of aircraft landing gear.
I'm not an engineer, but the first thing I asked myself after seeing the first designs of Starship is: how can they tail-land such a high obelisk with so little legs on an unknown terrain without capsizing?
How is it possible that SpaceX engineers didn't noticed a so evident design flaw?
#114 Re: Interplanetary transportation » Can we build an interstellar starship with current technology? » 2021-03-17 15:13:25
I have found this interesting article:
https://www.nasa.gov/directorates/space … /PROCSIMA/
https://ntrs.nasa.gov/api/citations/201 … 014041.pdf
In this study the laser beam is coupled with a neutral atom beam: the neutral atom flux is confined by the electromagnetic field of the laser, which creates a potential well (like the "kagome" used to confine the ultracold BEC atoms) and the atoms act like an optic fiber avoiding the diffraction spread of the photons and increasing the maximum acceleration distance and the final speed of the spacecraft.
The study is about a kilogram sized unmanned probe, so the topic of deceleration is not discussed. For a manned spaceship with laser stations at both ends of the trip, I have some doubt about the damage produced by the neutral atom impacts during the deceleration phase.
#115 Re: Interplanetary transportation » Can we build an interstellar starship with current technology? » 2021-03-16 04:55:11
Relying entirely on light pressure necessitates very powerful lasers. One way of reducing the required laser power would be to use the sail as a focusing mirror for a thermal rocket. The sail itself would be aluminium coated polymer. The focus would carry a crucible made from a high temperature ceramic. Hydrogen would be fed into the crucible and would boil to generate thrust.
A variation on this concept could make use of microwaves. The mirror would focus microwaves onto a focus. Hydrogen fired into the focus would be heated into a plasma, which would transfer momentum to the sail by means of a circumferential magnetic field. The problem with this idea is the generally poor beam coherence of microwaves. This concept would only work within a few hundred thousand km of a microwave source, for a sail with diameter 100km. To achieve high final speed requires high thrust and a lot of power.
Conceptually it works, but it might be very hard to do the engineering: a flat sail doesn't need any rigid stiffening rib and can be kept in shape only by centrifugal force. On the contrary a kilometer-sized spherical or parabolic mirror, acting also as a nozzle for hydrogen, needs strong stiffening ribs, resulting a huge weight.
Probably it may work better to use a smaller (30-40 meters) metallic mirror with a polyethylene cylinder in the focus as propellant, surrounded by 2 or 3 superconductive coil. Then use the laser in pulse to ablate the cylinder, resulting a high Isp propulsion for interplanetary travels. It's very simple and you have not to dial to the nasty hydrogen.
#116 Re: Interplanetary transportation » Can we build an interstellar starship with current technology? » 2021-03-16 04:38:07
In a post earlier in this topic, Quaoar showed a link to a paper that reported on study of a particular concept for nuclear fission spacecraft propulsion (the "dusty" method).
The paper contained a table which contained an entry that I did not understand. Quaoar confirmed that (in his judgement) the display of data from the table was correct and not a misprint
In his reply, Quaoar confirmed that the authors were imagining a projectile to be accelerated by their system that would have an atomic weight of 10 to the 8th power. Today I continued searching for a molecule of that mass.
I'd like to comment here upon the continuing and obvious advance of the AI that Google is constantly improving to help with search.
I entered the typical crude search request and it produced no useful results (lots of results but not what I wanted).
However, I rewrote the request in normal English: Please find a molecule with an atomic weight of 10^8
This time the top citation is an offering by a PhD chemist for calculation of the atomic weight (mass) of molecules.
I'm going to paste the link and a snippet, and am asking Chemistry majors (eg, PhD in the membership) to please follow the guidelines and post examples of molecules that would have the mass defined by the authors of the paper Quaoar cited for optimum performance of the "dusty" propulsion system.
https://www.thoughtco.com/how-to-find-m … ass-608487
By Anne Marie Helmenstine, Ph.D.
Updated November 06, 2019
The molecular mass or molecular weight is the total mass of a compound. It is equal to the sum of the individual atomic masses of each atom in the molecule. It's easy to find the molecular mass of a compound with these steps:Determine the molecular formula of the molecule.
Use the periodic table to determine the atomic mass of each element in the molecule.
Multiply each element's atomic mass by the number of atoms of that element in the molecule. This number is represented by the subscript next to the element symbol in the molecular formula.
Add these values together for each different atom in the molecule.The total will be the molecular mass of the compound.
(th)
10^8 is not the weight in atomic unit of a molecule, but of a dust grain of uranium 238, containing 10^8/238 atoms (about 420,000). It's uncommon to express the mass of metallic dust in atomic unit, but the authors treated the grains of the dusty plasma as they were a big molecule.
#117 Unmanned probes » Mars glacier mission to search bacteria » 2021-03-14 04:07:05
- Quaoar
- Replies: 16
Hi to all,
After the futuristic laser sail-starship, I would like to talk with you about something of more easy to do in the next years: an unmanned probe able to land on a glacier in an unnamed crater of the Vastitas Borealis (70.5° North and 103° East).
The lander will have a probe with an electric resistance able to melt the ice, penetrate for a meter or two, then aspirate some water samples, examine them with a microscope and send the images to Earth. Bacteria-like microbial life forms can be detected easily with a simple microscope (if we see no bacteria the probe can also make a culture incubating the water with organic material for some days). If the final result is positive, we can plan a sample return mission in the same place.
Just one bacteria-like alien organism can answer many of questions that torment the astrobiologists from years: is DNA the only possible genetic information-barer material for all the life forms, or in other planets the natural selection might have chosen other informational molecules (TNA, GNA, PNA are only example)?
https://en.wikipedia.org/wiki/Threose_nucleic_acid
https://en.wikipedia.org/wiki/Glycol_nucleic_acid
https://en.wikipedia.org/wiki/Peptide_nucleic_acid
There are hundreds of amino-acids, but the DNA of all the Earth's life forms uses only 20 of them as the building block of the living being. Is that choice ubiquitous, or there are alien organisms using completely different amino-acid sets?
I would like to know an expert opinion on the feasibility.
#118 Re: Interplanetary transportation » Can we build an interstellar starship with current technology? » 2021-03-13 15:13:24
Only 2.5kWe per person? Seems kind of low for something that has to feed its passengers for 20 years... that's at least 4 tonnes of food per passenger you're going to need to store, if they can stomach the sort of food that stores that long.
That's from a NASA study for a 18 months mission with a 6 crew transhab. I guess you are right and a 17 yrs interstellar mission needs much more kW/person: probably because it may be more convenient to have a near closed-cycle life support system, able produce food on board via hydroponics (in this case the reserve food supplies can be stowed near the habitat walls, to add passive shielding material).
#119 Re: Interplanetary transportation » Can we build an interstellar starship with current technology? » 2021-03-13 14:16:18
Nice origami very small package...
So the nuclear size still needs to be determined to match the size of the laser which is needed to push the ship to the near by sun....
My laser-stations are solar powered. Nuclear reactors are on the ship to produce energy during interstellar coasting (the ship has also some laser but only as a point-defense from space debris). Reactors size depends on the size of crew: almost 2.5 kWe/person plus the avionics and the instruments. If reactors are also used as FF-rocket for mid course corrections they need more power.
#120 Re: Interplanetary transportation » Can we build an interstellar starship with current technology? » 2021-03-13 13:03:06
Thank you Quaoar for the update of service to your country men as its showing what we will see in the future here as vaccines continue to roll out.
Its also a surprise to see that you doing coding as well as write SF novels....
The travel starts today for interstellar travel if we design the means to provide the power to the ship which would make it there.
A 20 year period of time for nuclear to survive does not seem all that hard if we do not activate it until we are mostly there as the energy for the ship can come from the system that pushes it towards the new suns to which it would orbit around.
Yes, it's not very hard: I imagine four sails (one main sail and three backup sails), four nuclear reactor for coasting (I'm exploring the possibility to use four FF-direct conversion-bimodal reactors, which can also be used as FF-rockets for mid-course corrections) https://en.wikipedia.org/wiki/Fission_fragment_reactor (during the acceleration and deceleration phases we can extract electric energy from the laser beam integrating into the sail some kind of thermionic converter). Attitude control can be done integrating into the sail some kind of variable reflectivity panel, like Ikaros did.
The habitat needs a 20 T superconductive coil to deflect GCR and must be surrounded by 25 cm of water or polyethylene to stop incoming neutral hydrogen atoms (i'ts interesting to note that the sail is almost transparent to neutral hydrogen at relativistic velocities) and four or five furling debris shield in 0.5 micron thick graphite-fiber-reinforced-graphite, which can also be used as laser-shadow shield. The sails have to be furled like an origami into a carbon-carbon ring of 100 m of diameter, with two habitat nacelles attached near the rim for artificial gravity and a central nacelle with all the navigation stuff in the middle.
https://d3i71xaburhd42.cloudfront.net/a … ure6-1.png
https://owdt-17dd0.kxcdn.com/wp-content … 649825.jpg
https://earth.esa.int/documents/163813/ … ros_Auto22
https://earth.esa.int/documents/163813/ … ros_Auto21
https://earth.esa.int/documents/163813/ … ros_Auto1F
https://earth.esa.int/documents/163813/ … ros_Auto1E
https://owdt.com/origamis-revolutionary … lications/
After the acceleration phase, the sail can be furled again inside the ring like, an origami, using carbon nanotube artificial muscle integrated into the stiffening ribs, in the same way the insects fold their wings inside their elytra.
https://pdfs.semanticscholar.org/ead5/6 … ef8a99.pdf
The life support radiator has to be put inside the ring, between the nacelles. That's the 10,000 ton Star Clipper of my next novel.
It's interesting to point out that at relativistic velocity a EVA will be fatal for a human, due to the impact of neutral hydrogen atoms, so all the extravehicular repairs have to be performed by drones.
#121 Re: Interplanetary transportation » Can we build an interstellar starship with current technology? » 2021-03-13 04:23:57
For Quaoar re new inter-solar-system code ...
It is encouraging to see you are willing to consider this imposition on your time ... I hope it will seem worth while ...
The chances of securing funding for a project seem greater (at least to me) if you can offer a way to reach Mars more rapidly than the current chemical rocket paradigm will allow.
There are some in the population of Earth who are enthusiastic about developing the Moon, in contrast to those who want to skip the Moon and go directly to Mars. The idea you've introduced into this forum might appeal to ** both ** camps!
There is competition shaping up between China and the rest of the world, to see who can establish dominance over Mars.
Your vision of a faster way to deliver goods and supplies, and collections of people to Mars may appeal to a small set of well connected folks.
Or, at a minimum, your work can lead to Science Fiction works that are focused upon the near term Solar System exploration.
***
I just received encouragement from Analog Science Fact and Fiction to offer them Fact articles based upon several initiatives in progress within the forum .... If you have not considered them as a market opportunity, please take a look ... they have a history of over 70 years of concentrating on the subset of Science Fiction you appear to be actively pursuing.(th)
I'm waiting for the call to be deployed in Sicily with the Italian Civil Protection Agency Vaccination Team. By the moment I have a lot of free time, but soon I'll be very busy.
#122 Re: Interplanetary transportation » Can we build an interstellar starship with current technology? » 2021-03-12 17:07:26
For Quaoar re topic ... I'd like to try to renew my inquiry about the possibility of using the technology you've imagined for an interstellar probe, for a much less exotic but perhaps quite useful application in the Earth-Mars transportation circuit.
It seems to me that a laser station can be installed and operated from the surface of the Moon (of Earth) while a comparable one can be installed for service from Phobos. The one on the Moon would be strong enough to propel a manned vessel (such as one of RobertDyck's Large Ships) toward Mars at a faster clip than is possible with simple chemical rocket propulsion. The one on Phobos would need to be strong enough to slow the vessel as it approaches Mars.
I would be ** most ** interested to see calculations your software might be able to provide, for such a system.
(th)
My software is optimized for interstellar travels, relativistic velocities, light years and direct radial acceleration, coast and deceleration from a star to another one. In a planetary system we have to compute fast orbital transfers so the math is different. I would have to write another code, but it's not a one-day-job.
#123 Re: Interplanetary transportation » Can we build an interstellar starship with current technology? » 2021-03-12 05:55:08
Beamed energy propulsion would require multiple terrawatts of power and an array of lasers capable generating beams with terrawatts of power. They will need to focus on a target perhaps a few tens of metres in diameter, at a distance of tens to hundreds of billions of kilometres.
With a 10,000 ton manned sail-ship, traveling with an initial acceleration of 9.8 m/s2, you need a 284.8 ton sail of 14.5 km of diameter, and a laser-station of 15.79 PWo@12 micron of wavelength with an array diameter of 1040 km, to focus at 2580 UA (the distance at which the acceleration phase ends). 15.78 TW of optical power, with lasers 0.9 efficient, needs 16.7 PW of electric power, with a photovoltaic array of 1104 km of diameter at 0.25 UA from the Sun (panels efficiency is 0.8%, very close to the theoric limit of 0.85%).
I am happy to be proven wrong, but this sounds like a project that would require huge amounts of infrastructure constructed in space. How feasible is it at a time when no human being has even ventured beyond low earth orbit in fifty years?
I agree that under some future scenario in which humanity has industrial scale space manufacturing, it may make sense to launch small interstellar probes using lasers mounted on solar power satellites. But we are nowhere near having those sorts of space manufacturing capabilities. It certainly would make sense establishing those sorts of capabilities, as they would have clear benefits in terms of supplying energy and valuable resources to people living on Earth. But interstellar probes will be a long-term side benefit of a space manufacturing programme. We need the horse before we can think about building elaborate buggies.
You are perfectly right: in this post I would only show how we can go interstellar without any new physic or technological breakthrough, like metallic hydrogen, room temperature superconductivity, antimatter production and storage system, fusion reactors or rockets, energy shields and warp drive, but only with the technologies we just have.
Take for example the 1942 B-29 Superfortress: all the technologies to build it (aluminium and piston-engines) were already present 39 years before, at the time of the first flight of the Wright Brothers' Flyer One. It was only a question of investing money in R&D to perfect them and pass from a little and rudimentary flight machine to a huge long range bomber. On the contrary the jet engine was a technological breakthrough, which lead to supersonic flight, infeasible at the times of Orville and Wilbur.
#124 Re: Interplanetary transportation » Can we build an interstellar starship with current technology? » 2021-03-12 04:20:46
For Quaoar ... May I (hopefully) entice you to open a new (less ambitious) line of inquiry?
To paraphrase an ancient saying ... it is good to walk before you run.
You could open a parallel topic: Can we build an interplanetary laser sailing craft with current technlogy?
I see no reason at all why the concept you've described for an interstellar journey could not be put to work here in the Solar System, with a laser station at the Moon at the Earth end, and one on Phobos at the Mars end.
Phobos needs impulse to keep it from descending further toward the Mars Roche limit, so pushing interplanetary vessels would (potentially) be helpful.
If you do decide to open a parallel line of inquiry, I hope you will consider a variety of scenarios offering a variety of velocities for consideration, and a variety of slow-down scenarios at Mars.
I do not approve of or support the use of the atmosphere of Mars to slow down vessels carrying humans, so hope you will consider avoiding that technique.
On the other hand, as the Ballistic Delivery topic shows, slowing non-living payloads in the atmosphere is practical and proven and potentially economical.
If your method can be adapted for the Ballistic Delivery case, I'd be quite interested to see your estimates.
(th)
By the moment the easiest way to Mars is a NTR spaceship, or a LOX-LCH4 Raptor powered spaceship with ISRU. We can build a laser-station on the Moon to propel a planetary sail-ship, but in this case the first Mars manned mission would be postponed of almost a century and nobody of us will ever see a human bean on the red planet. But in a future, once the laser-stations for interstellar travel have been built, they surely be also used for interplanetary travel, sparing a lot of propellant: we can image a digital currency: the sail-ship sends it to the station company and receives in exchange the beam.
With an interplanetary sail-ship the navigation technique is different: the sail has to be angled at 45° in the direction of the orbital motion (or in opposite direction) to change the orbit, and the laser has not to be so powerful, because 0.01 m/s2 accelerations are enough for deep-space navigation. Another valuable option might be to use the laser station to power the electric propulsion of an interplanetary spaceship: in this case we may have a variable thrust electric-drive (Cheng-Diaz's Vasimr might be an example), able to accelerate from 0.01 to 1 m/s2, that can be used either for impulsive, maneuver to leave planetary orbits, or to slowly accelerate in deep space, to reach Mars in three months.
lanetary sail-ship powered by laser-stations
#125 Re: Interplanetary transportation » Can we build an interstellar starship with current technology? » 2021-03-11 14:24:06
For Quaoar re Where is Proxima Centauri with respect to the Solar Plane ...
It would be helpful to have that information in the flow of this topic ... Your calculation puts acceleration duration at 111 days, which is more than one orbit of the Sun by Mercury. I expect that Proxima Centuri is ** NOT ** in the Solar Plane, so aiming should not be blocked by the Sun. There may well be other objects that are (or will be at the time) moving so they would intercept the beam.
Here is a Google snippet:
People also ask
Where is Proxima Centauri in the night sky?
Proxima Centauri can only be seen south of latitude 27°N. With an apparent magnitude of 11.05, it is is much too faint to be seen with the naked eye. It is in fact so faint that it would appear as a fifth magnitude star when observed from Alpha Centauri A or B.Jul 6, 2014Proxima Centauri | Constellation Guide
I'm not sure what it means, with respect to the question of it's location as we view it.
Here is a site that seems (as I understand it) to show that the Centauri system is well below the Solar Equatorial plane.
From Proxima to Toliman and Rigil Kentaurus are only 0.2 LY: think about what would have been easy for us to go interstellar if we were from Proxima: my sail-ship would have made the trip in 297.7 days of local reference time and 249.4 of ship-time, traveling at 0.25 C, with an initial acceleration of 9.8 m/s2 at constant power.
My interpretation is that there would be no obstruction of the beam from Mercury to propel a probe. I agree with Calliban that it would likely be easier to secure funding for a probe instead of trying for a full sized ship with crew.
Even a probe would be quite large (massive) it if includes the ability to slow down as it approaches the destination.
(th)
Sure. Even having laser-stations at both ends, before sending a manned sail-ship, we have to test our systems with unmanned probes, to prefect the laser-tracking system and the navigation system. Then we have to improve a lot our life support system technology to maintain alive the crew for all the 16.33 years of ship-time needed to reach Proxima at 0.25 C.