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No, I mean straight up--for the express purpose of using downward thrust.
Why are you ignoring the option provided by the existence of the caverns to avoid brute force surface drilling into the regolith?
Well, I'll try. Once you've deorbited and reconfigured the orbiter to nose-first reentry attitude ... in order to prevent burning-up as the air density increases more rapidly than aerodynamic drag can slow it down, simply tilt the nose up steeply to increase the drag and then use residual fuel to make downward-thrusting burns in order to control the rate of descent into the atmosphere.
Not retro rockets--but by conserving enough residual fuel to provide downward thrust as needed to reduce the rate of descent enough to prevent burning-up while aerodynamic drag slows down the space vehicle.
Since this topic was introduced, the so-called "Caverns of Mars" have been discovered . Lowering robots into them would bypass any need for heavy duty drilling equipment, since the equivalent of picks and shovels would be sufficient to get at the subsurface strata.
Why not provide an uninsulated reentry vehicle with (1) downward thrust rocket vectoring and (2) sufficient retained fuel aboard, to reduce the rate of descent into the atmosphere until commensurate with the reduction in velocity to avoid burning-up?
Extruding wire in orbit from masses of molten metal has its own problems, but gravity isn't one of them.
Confining solar heated molten masses in the case of aluminum or other nonferrous metal, as well as drawing through dies without an existing structure against which to pull opens up a whole, new field of heavy industry under microgravity conditions, in vacuum. There wouldn't be any size constraints out there. The initial assemblies could emulate spider webs, in concept, with Bigelow-type inflatable habitats positioned here and there as needed during assembly (themselves supported from within by wires in tension). Imagine initial single wire filaments being propelled across miles of space by spider-like tugs, to link up with previously deployed wires....
Why are you such a stickler for all-up, self-contained, definition of single-stage-to-orbit? What's the point? An airborne, airbreathing flyback first stage would be much preferred to a Saturn-like first stage, with reuseability making it commercially viable to start from airports anywhere in the world. If you really want to be picky, using the rotation of the Earth as a form of boost invalidates your ssto rocket claim, unless you launch it in a westerly direction to make your point--which would be just plane silly, right?
I don't think manufacturing metal stock, in the form of plates and beams, in space would be the way to start. How about extruding wires, which could be coiled prior to use, and then bent, twisted, braided, woven, and finally fused in place to form the various structural elements of the space station as needed, during construction?
And I feel compelled to reiterate that the so-called "caverns on Mars" shouldn't be overlooked during the first phase of exploration. Why no serious discussion of this, so far?
I should think that solar photovaic direct current would be by far the generation means of choice for energizing the "high temperature" superconducting coils.
I've read that a tenuous "arurora" would exist, but probably too faint for human eyesight to detect unaided. Suitably low light detection capability would provide a handy way to determin optimal coil positioning to accomodate differing spacecraft architectures while still in low-Earth-orbit, prior to any long duration mission.
Okay, according to Google: "M2P2 means MiniMagnetic Plasma Propulsion which is a system that can deliver energy from the solar wind to augument the onboard propulsion for spacecraft while minimizing the spacecraft power requirements. Potential for radiation shielding is still under investigation." The item wasn't dated.
Now, what is new is: the shielding potential has begun to be investigated by the Rutherford Lab group under Ruth Bamford, and (according to my post) results are promising. So it looks as if this (hopefully) last barrier to long-term job occupations in interplanetary space may be only temperary.
I do so hate acronyms. What the heck does m2p2 stand for?
Okay--so if gravity can be simulated aboard ship sufficiently to avoid human muscle/bone deterioration on extended space missions, perhaps it's time to seriously consider the so-far intractable problem of radiation damage to our cells from eg. solar flares? A recent development in the U.K. may hold the answer to this (hopefully) last remaining impediment to our occupation of the entire Solar System. Here it is:
[Quote] British scientists are working to build an invisible magnetic "Ion Shield" to be used during missions in space. A minature solar wind has been created in an Oxfordshire laboratory to simulate the highly charged particles emitted from the Sun and a magnetic "bubble" is being conceived to surround future spaceships. The magnetic field should have sufficient deflecting strength to redirect cancer-causing energetic particles away from future astronauts. Useful, especially during the proposed long-haul flights to Mars should the Sun begin launching flares at the wrong time.
The protection of astronauts in space from being bathed in damaging solar radiation is paramount to mission planners. Preventing exposure to high-energy particles is essential for the short-term success of the mission, and for the long-term health of the astronaut. Generally, humans in Earth orbit are protected from the ravages of the solar wind as they are within the protective blanket surrounding our planet. The protection is supplied by Earth's magnetosphere, a powerful magnetic shield that deflects charged particles and channels them to the north and south poles, allowing life to thrive down here on the surface. The particles injected into the poles react with our atmosphere generating light, the Aurora.
So, the UK team are looking to create a small-scale "magnetosphere" of their own. If a spaceship can generate its own magnetic field, then perhaps the majority of solar particles can be deflected, creating a protective bubble the ship can travel in during solar storms. This may sound like science fiction, but the physics is sound, magnetic fields are used every day to deflect charged particles. Why not try to build a spaceship-sized magnetic particle deflector?
"We now have actual measurements that show a 'hole' in the solar wind could be created in which a spacecraft could sit, affording some protection from 'ion storms', as they would call them on Star Trek." - Dr Ruth Bamford, physicist at the Rutherford Appleton Laboratory (RAL) in Chilton, Oxfordshire. [Unquote]
Aftercolumbia, regarding your quote:
"Another effect is cellular scenescense. If you have continuous rapid bone dissolution and bone growth, this increases the number of cell divisions necessary to maintain bone. Chromosomes have a ends called telomeres, they only permit between 50 and 100 divisions after conception then stop. This is the major aging clock. So rapid cell divisions just to maintain bone mass results in rapid aging. That's why starving yourself slows aging, it slows cell divisions. I could go into a long-winded argument of gene therapy to stop cellular scenescense and consequently stop most of aging, but there are some people who actually don't want aging to stop or slow down."
Where did you get that quote? It leaves out what would happen under greater than one-gee conditions. More to the point--would carrying around additional weight slow down your rate of cell division and thus allow you to have a potentially longer life?
Further re. the space cockroaches:
VORONEZH, January 17 (RIA Novosti) - Cockroaches conceived in space onboard the Russian Foton-M bio satellite have developed faster and become hardier than 'terrestrial' ones, a research supervisor said on Thursday.
The research team has been monitoring the cockroaches since they were born in October. The scientists established that their limbs and bodies grew faster.
"What is more, we have found out that the creatures... run faster than ordinary cockroaches, and are much more energetic and resilient," Dmitry Atyakshin said.
Cockroaches, as well as other types of insects, can give birth several times after one impregnation, and the cockroaches that conceived during the bio-satellite's September 14-26 flight have since given birth to their second and third batches of offspring.
"The second and third batches did not show these peculiarities of growth and physiology," the scientist noted.
'Ordinary' cockroaches are already known for their extraordinary resilience. Some species can last almost an hour without oxygen or a month without food, and are able to withstand high doses of radiation.
The September 14-26 flight was part of an ongoing experiment into the effects of space flight by the Institute of Biomedical Problems (IBMP). The creatures were sealed in special containers, and a video camera filmed them during the flight.
This just in (tail-end item of CBC Daily Planet popular science TV program today): Cockroaches bred and raised in microgravity by the Russians demonstrate on Earth heightened physical activity, mental capacity, and (dare I hope?) longevity. I didn't have time to follow this up, but maybe someone will before I get around to it....
Concerning longevity, though: besides musclularity, long life to have any meaning would have to include the brain and the continued development of the mind. I guess my question regarding optimum gravity really means something between one gee and zero gee. Excercise in lower than one gee conditions could still be accomplished. In fact, strapping on wings and flapping about in the air would be much more fun than pushups. The fact that blood supply to the brain need not be at risk as opposed to pooling in the legs for instance, might contribute to healthier brains. But, really, since we admittedly haven't yet performe the requisit experiments (mice raised at graduated centrifuge radii) I declare the argument for optimum longevity vs. gravity to be still open to discussion.
Okay, okay, I give in. But only because much of the engineering for the sample-and-return mission would be in place for the on-site remotely controlled sample analysis missions which undoubtedly will occur in-between the former and the first human missions. Since I won't be alive to witness the latter, dammit, I guess I'll have to settle for either or both of the two former.
What kind of shallow core sample would be worth all the time and expense to return it to Earth for analysis? We know it could be done, but a sample taken pretty much at random where the lander puts down hardly qualifies for all the effort expended to acquire it.
On the other hand, any lander designed for on-site analyses of multiple samples from differing spots within its range of excursion would necessarily be robust and powerful--as well as sophisticated enough to operated as (timelapsed)remote presence manipulators round-the-clock from Earth. Why not make this the breakthrough mission which utilizes a nuclear/electric power supply for the first time on Mars?
By alluding to the the complications involved in returning a sample of Mars's surface to Earth, I meant to show it up as a futile excercise in time and expense for little or no useful result. On site landers suitably equipped and remotely operated via orbiting links to and from Earth, not requiring realtime, would accomplish whatever was indicated by manipulators under offline control by scientists on Earth as the results of ongoing excavations, sample taking and analyses proceed for the operational life of the landers ... which may go on for years of Earth time, as opposed to the time restraints of sample and return missions.
As an aside, what about the so-called Caverns of Mars as potential sample sites? Compare mere surface scrapings, with the possibilities offered by these sites if the time expended in the engineering of sample and return schemes were applied to engineering access to the interior of Mars provided by these surprisingly little mentioned circular openings to the beneath the surface.
Regardless of what the samples might turn out to be, "return" should mean "return to low Earth orbit" (to prevent anything from the surface of Mars from ever entering our atmosphere) until having been investigated under quarntine conditions for any potential off world threat(s) to Earth's ecosphere. The time interval and trouble these precautions would entail, prompt me to recommend against robotic sample and return expeditions. Instead, we should develop robotically assisted sample and testing landers on Mars, where mobility time delay isn't the insurmountable problem that driving from Earth imposes. Tests and experiments at fixed location, using up to date remote operation techniques begining to be practiced by surgeons today, should be adaptable to answer any questions. Besides, the kinds of samples which can be scraped from the surface capable of being conveyed back to Earth aof analysis must be of minimal value compared with selected samples based upon repetitive analyses made at different locations within the operational radius of a fleet of mobile landers and their orbiting Earth/Mars links.
I've often wondered, since I'm getting on in age, if Earth gravity is necessarily optimum for human longevity. If, say, one lived on the Moon or Mars from birth, what might the average life span turn out to be--shorter, the same, or longer than here on Earth? How might this be investigated today? Perhaps populations of mice (say) born and living out their relatively shorter life spans than ours at various radii of a constant-speed centrifuge aboard the ISS could be used to form a first approximation answer to this question.
Well, I should've thought of the Earth-Sun Lagrange points myself. But having approached the delimma intuitively as an objection to treating LEO and (solar orbiting) asteroid access to construction materials similarly, I got carried away. Still, if one is willing to actively control the hypothetical asteroid colony in order to maintain a distance roughly a week or two away from Earth, and by inclining and elongating the orbit around the Sun to match our period of one year, wouldn't this be handy expedient during the construction phase?
"It's possible that they never worked properly but it wasn't detected."
Cripes! Another unforseen "Russian roulette" type design detail to contend with--after all this time?