-The shock wave from the supernova (which is rich in heavy elements) will sweep up interstellar gas until the total supernova remnant will be a shell of hundreds -or even thousands- of solar masses of gas, sometimes with a neutron star or a black hole in the center remaining of the star.
If one part of the supernova remnant has swept up enough gas, the compressed gas can begin to contract under its own gravity to create the next generation of stars.
Typically, when a big nebula begins to collapse, the heaviest fragments contract first, creating short-lived giant stars that explode and seed the rest of nearby space with heavy elements. The shock waves then fragment and contract into new proto-stars, with sizes distributed from many very small red dwarf stars to a few bigger stars.
If you could build a big hypersonic Mach-10 craft it could be used as a first stage for a launcher.
An air-breathing first stage with a speed of 3-3.5 km/s could carry a cheap rocket that after separation takes a satellite all the way to orbit.
This is the opposite of the shuttle, who uses a low-tech first stage (the solid-fuel boosters) to carry a high-tech reusable last stage (the shuttle) which is so weighed down with heat shielding and aerodynamic structures that it cannot carry much to orbit.
Unfortunately, a scramjet will be of little use without heat-resistent materials that will allow you to design a streamlined spaceplane . The shuttle is blunt and "tubby" because this way the hot plasma fireball is kept ahead off the nose, but it creates very high drag. The more streamlined you make the spaceplane, the less drag, but also the more heating at the "sharp" nose and wings. Today's ceramic materials are way too brittle, and today's metal alloys would quickly melt.
In theory, Venus ejecta might have been launched during the early "era of heavy bombardment", when the solar system was young and Venus had not yet undergone a "runaway greenhouse" and had a thin atmosphere. Both Earth and Venus were repeatedly hit by very large planetesimals, and would have ejected much material into space.
Any venusian rocks that hit Earth would have been destroyed by erosion or tectonic activity long ago, but in theory there might be rocks from both the young Venus and the young Earth buried under a thick layer of regolith on the *moon*, since apart from impacts, the lunar surface has not been altered much since the solar system was young. However, such rocks would be very small needles in a very large haystack. Even if they look different from most lunar rocks (because their surfaces would show signs of ablation from when they were ejected upards through the atmosphere) I do not recommend anyone to spend much time looking for them. The difficulties of finding such rocks might well be as immense as trying to find preserved dinosaur DNA here on Earth:-)
It would be very interesting to find a pristine rock from either Phobos or the Martian surface before the object gets contaminated by the terrestrial environment -meaning before they fall on Earth ! Phobos -which is believed to have started off as an asteroid- might have the molecular building blocks for life, but the researchers want to be sure they are not just seeing earthly contaminants. And a rock from Mars' surface might have fossil bacteria, but such stuctures might also have been created after arriving on Earth.
One way to retrieve such rocks in space is to look for big chunks that have settled in the L4/L5 regions of Mars' orbit after having been ejected by big impacts, and then send a spacecraft with an ion engine to take samples -much simpler than sending a sample return mission to the martian surface, or even to Phobos, since there is no strong gravity from a twenty-metre rock.
Identifying such rocks would require a combination of spectroscopy (both visual light and IR) and dynamical considerations: An object near Mars' L4 or L5 points is more likely to have come from Mars than from the asteroid belt. Even if the probe on arrival finds the rock is a chunk of Phobos instead of a genuine Mars rock, it will still have great scientific interest.
And compared to near-Earth asteroids, Phobos rocks will have experienced lower temperatures and might retain more volatile compounds.
This news gave me an idea about providing samples of Martian rock without going into the gravity well of Mars, and I would like you to point out any fallacies in my reasoning.
If the Earth-Moon system has pseudo-satellites, so will Mars. The orbital perturbations by Jupiter will eventually remove them, but on the other hand the vicinity to the asteroid belt will cause many more impacts, creating new pseudosatellites to Mars.
These pieces of martian rock will not be contaminated like the meteorites found in the Antarctic, nor do they require a very complex sample return mission. Ion engines, or even ordinary chemical engines would be suitable, and there is no need for heat shields, parachutes, or in-situ propellant production. Maybe even a private organization might have the the resources required ?
Ordinary asteroids in the inner solar system sometimes pass in front of weak background stars (occultations), which provides the opportunity to measure their diameters by timing the disappearence and reappearence of the star. Sometimes such occultations even have revealed the asteroid to be binary. However, such events are rare, even for close-by asteroids. The angular diameter of far-away Kuiper-Edgeworth objects is so small that they almost never pass in front of a catalogued star. -The basic idea is sound, it is just very unlikely that a K-E object will pass in front of a star that is under observation.
For descriptions of what swarmbots might be like in real life, I recommend three novels by Stanislaw Lem ; "The Invincible" (about self-evolving swarmbots), "Peace On Earth" and finally "Fiasco" where swarmbots ("synsects") are used as information collectors. In "Peace On Earth" there is also mentioned the possibility that swarmbots may assemble to create larger military machines in an era when automated battlefield surveillance will make it suicidal for a conventional large vehicle to try to cross a battlefield. Yours Birger Johansson.
I assume you mean *multicellular* life, or possibly *intelligent* life. The Vega system should be just old enough for the first primitive life forms to have emerged -This could mean an opportunity to observe the very transition from a "pre-DNA world" (based om RNA or even more primitive genetic substrates) to a "DNA world" -this is itself probably even more interesting than watching the planet-forming process around Vega.
Addendum: I misunderstood the age, the system is 350 million years, not 30. However, at that age, giant impacts will still hit any planets with "dinosaur-killer" asteroids at a rate hundreds of times more often than our Earth. Some of those rocks will even be big enough to vaporize the oceans, after it will take thousands of years for a planet to recover from the thermal shock.
Also, planets need time to create a differentiated crust, and if water is present in large amounts on a planet (on a scale compareable with Earth) tectonic processes need hundreds of milions of years to start differentiating "continental" crust that rises above the ocean. There will be plenty of volcanic islands in such an Ur-ocean, but initially there will be no large land masses at all. Everything will be pelted by giant impacts over and over again, some of them big enough to cause tsunami that completely drench smaller islands, a few big enough to boil the seas and the biosphere. Nevertheless, there could well be life at the bottom of the oceans, protected from the violence of impacts by living in rock fissures very deep under the ocean floor.
-Since the Vega system is very young, any terrestrial planets will probably not yet be in a "finished" state, but will still be busy accreting smaller planetesimals- for the Earth, this initial process might have taken 30 million years. Also, any such planets will not have finished differentiating into a core, a mantle and a crust. If you send a probe there, it will not be able to find a cool surface on any of the larger planetesimals (growing proto-planets). The Vega system is interesting because it provides a snapshot of the early phase of planet formation. If you want to make a "Star Trek" style tour of a system, landing on the planets and checking for the presence of life, you need to find a more "mature" system, where the planetary crusts have had time to cool off, and where most of the orbiting debris has alredy been swept up by planets.
One other interesting point about the Vega system though: It is bound to have an amazing number of large, highly visible comets ! In mature systems, most comets have either been kicked out to the Oort cloud or crashed into a planet.
A couple of years ago, a journal (Nature or Science) had an article about how hibernatig bears have the ability to remain still for months without losing muscle mass. To cope with microgravity during long periods, it would be very useful to use GM technology to "upgrade" people to have this ability. -In regard to suspended animation (I am here referring to the less difficult option of reducing metabolism *without* freezing the organism), unlike the hearts of hibernating mammals, human hearts begin to fibrillate when the core body temperature drops below a certain treshold. This problem must be solved before any suspended animation can be considered.
Space elevators are one of three basic "space tether" concepts, and it would be logical to start with more humble objectives.
The simplest form of a space tether is essentially a high-tech version of that bronze-age weapon, the sling. A tether for sending satellites to higher orbits, or spacecraft on lunar or planetary trajectories can be achieved with *existing* materials, like kevlar or spectra. This form of tether concept is being investigated by NASA.
A second form of space tether -the hypersonic skyhook- is described in Zubrin's and Schmidt's book "Islands In the Sky". In the example with a hypersonic skyhook whose lower end is travelling at 5 km/s relative to the surface of Earth, the total mass of the system need only be 20 times that of the load. The launcher need only travel at the same speed as the end of the tether, and -here is the tricky part- the cargo module then has to manouver for some hair-raising seconds to hover at ca. 0.5 g in order to dock with the end of the skyhook. After that, it can travel up the tether like a elevator car, and the tether can interact with the Earth's magnetic field to regain the kinetic/potential energy lost simply by running a current through a cable. The difference between a minimum velocity of 5 km/s and 8 km/s (low-earth orbit) is enormous in terms of the launcher/payload mass ratio, and could make single-stage to orbit (SSTO) rockets viable with *current* technology.
The space elevator is the third and most technically difficult form of space tether, and it should be attempted last. It can only be built by bulk production of carbon nanotube materials and this is still far into the future.
Actually, the original article states that the concept "first gained *widespread* attention when the science fiction writer Arthur C Clarke described it in his 1979 novel Fountains of Paradise".
The concept had been invented independently both in USA and the Soviet Union long before the book was written -Arthur C. Clarke's great contribution is bringing the concept to a wider audience. (The cosmonaut Leonov had actually made a painting depicting a space elevator, but westerners -ignorant of the concept studies being done- thought he was nuts)
BTW, I was in contact with ACC two yeras ago and asked him about this novel. He mentioned that the scientist who helped him with the facts was non other than Buckminster Fuller, the discoverer of "buckminsterfullerene".
It so happens that the carbon nanotubes which have the tensile strength to make the cable possible are simply tubular versions of buckminsterfullerene. Fuller himself was not aware of this ironic fact, the nanotubes were only produced in the lab and had their strength measured in the nineties, after Buckminster Fuller's death.
It has been done by the Russians. The oldest launcher in use in the world -the R-7 Soyuz- is basically the same that was used or Sputnik 1 1957. The current design version has been the same since 1967. By sticking to the same design, the russians have produced a very reliable and cheap launcher that -despite the technologica abyss between R-7 and the much later Shuttle- cost no more per pound to orbit than the Shuttle !
The french are actually license-building the R-7 as a complement to their own line of more modern rocket launchers like Ariadne.
Since asteroids contain all kinds of useful elements, and since the moon is sadly deficient in many important elements -to the grief of those who make plans for permanent space colonization- it would make sense to give the asteroid a gente nudge with a nuclear engine to send it crashing into the moon.
The Earth itself has received much valuable elements from asteroid impacts during the past 4 billion years (check the Sudbury impact site), and while no one wants an asteroid to hit the Earth today, there are no lunar inhabitants that might get hurt.
If it crashed at a very shallow angle, the scattered lunar regolith will dissipate the kinetic energy without vaporizing the asteroid fragments. This will give future lunar colonists a rich supply of substances containing nitrogen, carbon, and possibly even hydrated minerals.
The book "islands in the Sky" by Schmidt and Zubrin presents a viable alternative to using full-scale SSTOs and other launchers by applying existing high-strength materials such as spectra or kevlar. The concept is called a "hypersonic skyhook". *Unlike* a full-sized space elevator, it only needs to be twenty times heavier than the load it lifts into a permanent orbit.
Very briefly, if a cable (with a center of gravity at an altitude where the orbital velocity is ca 5,5 km/second) extends down to ca 200 km (where the orbital velocity is ca. 7.5 km/s) it means you can let a humble* suborbital vehicle latch on to the cable end. In an equatorial orbit, you get an extra 0.5 km/s free of charge. You only need a vehicle able to reach a velocity of 5 km/s and hover for half a minute while locking on to the business end to the cable, after which it can let the cargo module go along with the hypersonic skyhook.
This is doable with current technology, and could be done with a fraction of the money that is spent on "white elephants" like the ISS.
(*=By "humble suborbital vehicle" I mean the difference between 5km/s and 7.5 km/s means a reduction of size, cost and complexity by several orders of magnitude, compared to a SSTO like Venture Star)
-As a matter of fact, the chinese have already done what you suggest, and built a modified version of Soyuz for their own manned space program. This is a very obvious, cost-effective and safe way to go, but national pride will rule out this option. Let us however assume logic prevails. In that case, a slightly upgraded russian R-7 (Soyuz) launcher could carry an upgraded Souyz derivative with capacity for four persons. The current version of R-7 is from 1967 and uses kerosene/LOX in all stages. A bigger derivative of the old US Centaur stage (with hydrogen and LOX) as the last R-7 stage should be able to carry four astronauts to ISS and to Hubble servicing missions at a fraction of the cost of launching the shuttle. Nearly all the stuff would be off-the-shelf.
BTW, the french are building a launch pad at Kourou for the R-7 since they like its low cost and reliability. If you launch from an equatorial site (instead from Russia) an ordinary R-7/ordinary Soyuz combination could be used for servicing Hubble -without modifications !
It is even better: there is so much water in "iceteroids" like the Centaurs, Trans-Neptune objects or Trojans that it would suffice to provide Mars with oceans even if Mars currently is bone dry, and even if only a fraction of those objects were diverted to Mars. These objects are not stuck inside any gravity well, and with appropriate gravity assists an enormous amount of water could be sent on its way by using very little "delta-vee". Five years ago, when 1996TL66 -a hundred-kilometer object- was discovered, I worked out that a velocity change of less than 0.2 km/s at aphelion could bring it to the vicinity of Neptune for a gravity assist, and when better telescopes are built we will no doubt find many other "iceteroids" that are even better suited.
For such a robot [or any other independent robot] to find many practical applications, it would need good visual pattern-recognition software to navigate independently, which is a very difficult objective due to the processing power needed, but quantum physics may help.
A year ago, New Scientist wrote about an algorithm that might allow future quantum computers to make a "Fourier transform" for pattern recognition. -If such quantum computers can ever become reality [with their massively parallel processing capacity], and fit into a robot that is resilient enough to adapt to damage, the we have literally a "killer application": tiny battlefield robots that can operate without supervision.
Twenty years ago, in the novel "Peace On Earth", Stanislaw Lem predicted that when small robots became smart and robust enough to operate on their own in the battlefield, it would have an effect similar to the stagnant battlefields of the first world war; conventional warfare would no longer be possible.
Assume the battlefield is full of small, self- repairing robots that can spot anything bigger than a bird or rodent moving about -it would no longer be possible to send tanks or even larger infantry units across without suffering devastating losses.
The reason sevicing missions to Hubble are so expensive is that NASA only has one manned spacecraft design: the expensive and not quite safe space shuttle.
The much cheaper Soyuz craft are usually launched from Kazakhstan, thus giving them the wrong *orbital inclination* for a rendezvous with Hubble, but the French launch site at Kourou has a R7/Soyuz-compatible launch pad under construction.
The reason the French are planning to use the Russian R 7 launcher is that the R 7 is extremely reliable, and as cheap per pound to orbit as the space shuttle. If NASA could put pragmatism before prestige, Souyz missions to Hubble could be launched from Kourou at a fraction of the cost of launching the 2000-ton shuttle/solid fuel booster combination.
If it was necessary to add rockets to send Hubble into a higher "mothballing" orbit, a Progress capsule could be launched with the heavy load that could not be sent along with a Soyuz. This would take two R7 launches (one crewed Soyuz, one unmanned Progress) -still a trivial cost compared to a single shuttle launch. Also, the Souyz is a thoroughly proven, simple and safe design, so the crew would not be in any danger. The problem is not technology, but politics: The NASA administrators would rather let Hubble burn in the atmosphere than admit a 35-year old foreign design is better than the shuttle for the job.
Alas, there is still a long way to go before space elevators can be built.
The strength of this material will be suffice for space "tethers" that can work as slings to catapult loads into higher orbits, or even give them escape velocity.
Genuine space elevators require a strength several orders of magnitude greater, but the maximum strength of individual nanotubes makes it theoretically possible to get there. For details, see an article in American Scientist (NOT Scientific American) 5-7 years ago. It discussed the minimum strength required, and the reasons carbon nanotubes just might work.
Ironically, Buckminster Fuller, the discoverer of Buckminsterfullerene (carbon nanotubes can be seen as tubular extensions of these molecules), was a friend of Arthur C. Clarke, the author of the first space elevator novel "The Fountains of Paradise". Neither Fuller nor Clarke suspected that Fuller's discovery one day might serve as the foundation to high-strenght materials that could make space elevators possible ! Yours Birger J.
I would love a genuine discovery of venusian life.... Unfortunately, Venus has a different, more violent form of tectonic resurfacing than the slow plate tectonics on Earth. Judging by the number of craters on the surface, the entire surface of Venus melted ca. 600 million years ago, as the build-up of internal heat made the crust crack up and hot magma totally covered the surface.
Even if life was present high up in the atmosphere, the heat of the ground was much higher than today, and would have been carried upwards, frying any airborne microbes. Adiabatic cooling makes air cool with altitude, but to escape the heat of a molten-lava surface, any airborne life would have had to migrate up to altitudes with very thin air, much higher than the layer where the interesting molecules are found today. While thick air might carry microbes, I do not see how life could survive and thrive in a stratospheric near-vacuum. Yours Birger J.
Although Sir Fred Hoyle proposed *complete* organisms might have developed in space, this is a partial vindication of his ideas.
He was sometimes ridiculed for some of his wilder ideas, which caused his more resonable ideas to be ignored; It is a pity he did not live a few additional months, to read this news.
One aspect other postings have neglected is the low probability a lone impactor should hit near a center of bronze-age civilization.
It is unlikely that the impactor was the only object, or even one of a few objects, involved in the impact; it was likely one of several fragments from a disrupted "rubble-pile" asteroid hitting the Earth.
Statistically, a meteorite is far more likely to hit the Pacific, or the Sahara than, say, New York or some other center of civilization.
Mesopotamia was one of the few centers of civilization of the period. If Mesopotamia was hit, it makes sense to assume that it was part of a "shotgun blast" of many impacts.
Some objects (like the precursor to comet SL-9 that hit Jupiter) are loosely bound "rubble piles" only held together by gravity.
If the impactor was a fragment of a loosely bound object, broken up by tidal forces during a previous near miss (like SL-9), it would have been a member of a swarm of objects hitting the Earth.
The probability that Mesopotamia would be hit was high, since the probability was high *everywhere*.
There might be many other impact sites buried under sediments around the world, or maybe most fragments were too small to survive atmospheric entry.
Most would have hit the ocean; if tsunami-generated deposits can be dated, it would be interesting to see if there is a cluster near 2300 B.C.
Slashdot Mirror
-The shock wave from the supernova (which is rich
in heavy elements) will sweep up interstellar gas
until the total supernova remnant will be a shell
of hundreds -or even thousands- of solar masses
of gas, sometimes with a neutron star or a black
hole in the center remaining of the star.
If one part of the supernova remnant has swept up
enough gas, the compressed gas can begin to contract
under its own gravity
to create the next generation of stars.
Typically, when a big nebula begins to collapse,
the heaviest fragments contract first, creating
short-lived giant stars that explode and seed the
rest of nearby space with heavy elements.
The shock waves then fragment and contract into new
proto-stars, with sizes distributed from many very
small red dwarf stars to a few bigger stars.
Yours Birger Johansson, Sweden
If you could build a big hypersonic Mach-10 craft it could be used as a first stage for a launcher.
An air-breathing first stage with a speed of 3-3.5 km/s could carry a cheap rocket that after separation takes a satellite all the way to orbit.
This is the opposite of the shuttle, who uses a low-tech first stage (the solid-fuel boosters) to carry a high-tech reusable last stage (the shuttle) which is so weighed down with heat shielding and aerodynamic structures that it cannot carry much to orbit.
Unfortunately, a scramjet will be of little use without heat-resistent materials that will allow you to design a streamlined spaceplane . The shuttle is blunt and "tubby" because this way the hot plasma fireball is kept ahead off the nose, but it creates very high drag.
The more streamlined you make the spaceplane, the less drag, but also the more heating at the "sharp" nose and wings. Today's ceramic materials are way too brittle, and today's metal alloys would quickly melt.
In theory, Venus ejecta might have been launched during the early "era of heavy bombardment", when the solar system was young and Venus had not yet undergone a "runaway greenhouse" and had a thin atmosphere.
:-)
Both Earth and Venus were repeatedly hit by very large planetesimals, and would have ejected much material into space.
Any venusian rocks that hit Earth would have been destroyed by erosion or tectonic activity long ago, but in theory there might be rocks from both the young Venus and the young Earth buried under a thick layer of regolith on the *moon*, since apart from impacts, the lunar surface has not been altered much since the solar system was young.
However, such rocks would be very small needles in a very large haystack. Even if they look different from most lunar rocks (because their surfaces would show signs of ablation from when they were ejected upards through the atmosphere) I do not recommend anyone to spend much time looking for them.
The difficulties of finding such rocks might well be as immense as trying to find preserved dinosaur DNA here on Earth
It would be very interesting to find a pristine rock from either Phobos or the Martian surface before the object gets contaminated by the terrestrial environment -meaning before they fall on Earth !
Phobos -which is believed to have started off as an asteroid- might have the molecular building blocks for life, but the researchers want to be sure they are not just seeing earthly contaminants. And a rock from Mars' surface might have fossil bacteria, but such stuctures might also have been created after arriving on Earth.
One way to retrieve such rocks in space is to look for big chunks that have settled in the L4/L5 regions of Mars' orbit after having been ejected by big impacts, and then send a spacecraft with an ion engine to take samples -much simpler than sending a sample return mission to the martian surface, or even to Phobos, since there is no strong gravity from a twenty-metre rock.
Identifying such rocks would require a combination of spectroscopy (both visual light and IR) and dynamical considerations: An object near Mars' L4 or L5 points is more likely to have come from Mars than from the asteroid belt.
Even if the probe on arrival finds the rock is a chunk of Phobos instead of a genuine Mars rock, it will still have great scientific interest.
And compared to near-Earth asteroids, Phobos rocks will have experienced lower temperatures and might retain more volatile compounds.
This news gave me an idea about providing samples of Martian rock without going into the gravity well of Mars, and I would like you to point out any fallacies in my reasoning.
If the Earth-Moon system has pseudo-satellites, so will Mars. The orbital perturbations by Jupiter will eventually remove them, but on the other hand the vicinity to the asteroid belt will cause many more impacts, creating new pseudosatellites to Mars.
These pieces of martian rock will not be contaminated like the meteorites found in the Antarctic, nor do they require a very complex sample return mission.
Ion engines, or even ordinary chemical engines would be suitable, and there is no need for heat shields, parachutes, or in-situ propellant production. Maybe even a private organization might have the the resources required ?
Yours
Birger Johansson
Ordinary asteroids in the inner solar system sometimes pass in front of weak background stars (occultations), which provides the opportunity to measure their diameters by timing the disappearence and reappearence of the star. Sometimes such occultations even have revealed the asteroid to be binary.
However, such events are rare, even for close-by asteroids. The angular diameter of far-away Kuiper-Edgeworth objects is so small that they almost never pass in front of a catalogued star.
-The basic idea is sound, it is just very unlikely that a K-E object will pass in front of a star that is under observation.
For descriptions of what swarmbots might be like in real life, I recommend three novels by Stanislaw Lem ; "The Invincible" (about self-evolving swarmbots),
"Peace On Earth" and finally "Fiasco" where swarmbots ("synsects") are used as information collectors. In "Peace On Earth" there is also mentioned the possibility that swarmbots may assemble to create larger military machines in an era when automated battlefield surveillance will make it suicidal for a conventional large vehicle to try to cross a battlefield.
Yours Birger Johansson.
I assume you mean *multicellular* life, or possibly *intelligent* life. The Vega system should be just old enough for the first primitive life forms to have emerged
-This could mean an opportunity to observe the very transition from a "pre-DNA world" (based om RNA or even more primitive genetic substrates) to a "DNA world" -this is itself probably even more interesting than watching the planet-forming process around Vega.
Addendum: I misunderstood the age, the system is 350 million years, not 30.
However, at that age, giant impacts will still hit any planets with "dinosaur-killer" asteroids at a rate hundreds of times more often than our Earth. Some of those rocks will even be big enough to vaporize the oceans, after it will take thousands of years for a planet to recover from the thermal shock.
Also, planets need time to create a differentiated crust, and if water is present in large amounts on a planet (on a scale compareable with Earth) tectonic processes need hundreds of milions of years to start differentiating "continental" crust that rises above the ocean. There will be plenty of volcanic islands in such an Ur-ocean, but initially there will be no large land masses at all. Everything will be pelted by giant impacts over and over again, some of them big enough to cause tsunami that completely drench smaller islands, a few big enough to boil the seas and the biosphere.
Nevertheless, there could well be life at the bottom of the oceans, protected from the violence of impacts by living in rock fissures very deep under the ocean floor.
-Since the Vega system is very young, any terrestrial planets will probably not yet be in a "finished" state, but will still be busy accreting smaller planetesimals- for the Earth, this initial process might have taken 30 million years. Also, any such planets will not have finished differentiating into a core, a mantle and a crust.
If you send a probe there, it will not be able to find a cool surface on any of the larger planetesimals (growing proto-planets).
The Vega system is interesting because it provides a snapshot of the early phase of planet formation.
If you want to make a "Star Trek" style tour of a system, landing on the planets and checking for the presence of life, you need to find a more "mature" system, where the planetary crusts have had time to cool off, and where most of the orbiting debris has alredy been swept up by planets.
One other interesting point about the Vega system though: It is bound to have an amazing number of large, highly visible comets ! In mature systems, most comets have either been kicked out to the Oort cloud or crashed into a planet.
Yours Birger Johansson Sweden
A couple of years ago, a journal (Nature or Science) had an article about how hibernatig bears have the ability to remain still for months without losing muscle mass.
To cope with microgravity during long periods, it would be very useful to use GM technology to "upgrade" people to have this ability.
-In regard to suspended animation (I am here referring to the less difficult option of reducing metabolism *without* freezing the organism), unlike the hearts of hibernating mammals, human hearts begin to fibrillate when the core body temperature drops below a certain treshold.
This problem must be solved before any suspended animation can be considered.
Space elevators are one of three basic "space tether" concepts, and it would be logical to start with more humble objectives.
The simplest form of a space tether is essentially a high-tech version of that bronze-age weapon, the sling. A tether for sending satellites to higher orbits, or spacecraft on lunar or planetary trajectories can be achieved with *existing* materials, like kevlar or spectra.
This form of tether concept is being investigated by NASA.
A second form of space tether -the hypersonic skyhook- is described in Zubrin's and Schmidt's book "Islands In the Sky". In the example with a hypersonic skyhook whose lower end is travelling at 5 km/s relative to the surface of Earth, the total mass of the system need only be 20 times that of the load. The launcher need only travel at the same speed as the end of the tether, and -here is the tricky part- the cargo module then has to manouver for some hair-raising seconds to hover at ca. 0.5 g in order to dock with the end of the skyhook. After that, it can travel up the tether like a elevator car, and the tether can interact with the Earth's magnetic field to regain the kinetic/potential energy lost simply by running a current through a cable.
The difference between a minimum velocity of 5 km/s and 8 km/s (low-earth orbit) is enormous in terms of the launcher/payload mass ratio, and could make single-stage to orbit (SSTO) rockets viable with *current* technology.
The space elevator is the third and most technically difficult form of space tether, and it should be attempted last. It can only be built by bulk production of carbon nanotube materials and this is still far into the future.
Actually, the original article states that the concept "first gained *widespread* attention when the science fiction writer Arthur C Clarke described it in his 1979 novel Fountains of Paradise".
The concept had been invented independently both in USA and the Soviet Union long before the book was written -Arthur C. Clarke's great contribution is bringing the concept to a wider audience. (The cosmonaut Leonov had actually made a painting depicting a space elevator, but westerners -ignorant of the concept studies being done- thought he was nuts)
BTW, I was in contact with ACC two yeras ago and asked him about this novel. He mentioned that the scientist who helped him with the facts was non other than Buckminster Fuller, the discoverer of "buckminsterfullerene".
It so happens that the carbon nanotubes which have the tensile strength to make the cable possible are simply tubular versions of buckminsterfullerene. Fuller himself was not aware of this ironic fact, the nanotubes were only produced in the lab and had their strength measured in the nineties, after Buckminster Fuller's death.
Yours Birger Johansson
It has been done by the Russians. The oldest launcher in use in the world -the R-7 Soyuz- is basically the same that was used or Sputnik 1 1957. The current design version has been the same since 1967. By sticking to the same design, the russians have produced a very reliable and cheap launcher that -despite the technologica abyss between R-7 and the much later Shuttle- cost no more per pound to orbit than the Shuttle !
The french are actually license-building the R-7 as a complement to their own line of more modern rocket launchers like Ariadne.
Since asteroids contain all kinds of useful elements, and since the moon is sadly deficient in many important elements -to the grief of those who make plans for permanent space colonization- it would make sense to give the asteroid a gente nudge with a nuclear engine to send it crashing into the moon.
The Earth itself has received much valuable elements from asteroid impacts during the past 4 billion years (check the Sudbury impact site), and while no one wants an asteroid to hit the Earth today, there are no lunar inhabitants that might get hurt.
If it crashed at a very shallow angle, the scattered lunar regolith will dissipate the kinetic energy without vaporizing the asteroid fragments. This will give future lunar colonists a rich supply of substances containing nitrogen, carbon, and possibly even hydrated minerals.
Yours Birger Johansson
The book "islands in the Sky" by Schmidt and Zubrin presents a viable alternative to using full-scale SSTOs and other launchers by applying existing high-strength materials such as spectra or kevlar. The concept is called a "hypersonic skyhook". *Unlike* a full-sized space elevator, it only needs to be twenty times heavier than the load it lifts into a permanent orbit.
Very briefly, if a cable (with a center of gravity at an altitude where the orbital velocity is ca 5,5 km/second) extends down to ca 200 km (where the orbital velocity is ca. 7.5 km/s) it means you can let a humble* suborbital vehicle latch on to the cable end. In an equatorial orbit, you get an extra 0.5 km/s free of charge.
You only need a vehicle able to reach a velocity of 5 km/s and hover for half a minute while locking on to the business end to the cable, after which it can let the cargo module go along with the hypersonic skyhook.
This is doable with current technology, and could be done with a fraction of the money that is spent on "white elephants" like the ISS.
(*=By "humble suborbital vehicle" I mean the difference between 5km/s and 7.5 km/s means a reduction of size, cost and complexity by several orders of magnitude, compared to a SSTO like Venture Star)
Yours Birger Johansson
-As a matter of fact, the chinese have already done what you suggest, and built a modified version of Soyuz for their own manned space program. This is a very obvious, cost-effective and safe way to go, but national pride will rule out this option.
Let us however assume logic prevails. In that case, a slightly upgraded russian R-7 (Soyuz) launcher could carry an upgraded Souyz derivative with capacity for four persons. The current version of R-7 is from 1967 and uses kerosene/LOX in all stages.
A bigger derivative of the old US Centaur stage (with hydrogen and LOX) as the last R-7 stage should be able to carry four astronauts to ISS and to Hubble servicing missions at a fraction of the cost of launching the shuttle. Nearly all the stuff would be off-the-shelf.
BTW, the french are building a launch pad at Kourou for the R-7 since they like its low cost and reliability. If you launch from an equatorial site (instead from Russia) an ordinary R-7/ordinary Soyuz combination could be used for servicing Hubble -without modifications !
It is even better: there is so much water in "iceteroids" like the Centaurs, Trans-Neptune objects or Trojans that it would suffice to provide Mars with oceans even if Mars currently is bone dry, and even if only a fraction of those objects were diverted to Mars.
These objects are not stuck inside any gravity well, and with appropriate gravity assists an enormous amount of water could be sent on its way by using very little "delta-vee".
Five years ago, when 1996TL66 -a hundred-kilometer object- was discovered, I worked out that a velocity change of less than 0.2 km/s at aphelion could bring it to the vicinity of Neptune for a gravity assist, and when better telescopes are built we will no doubt find many other "iceteroids" that are even better suited.
For such a robot [or any other independent robot] to find many practical applications, it would need good visual pattern-recognition software to navigate independently, which is a very difficult objective due to the processing power needed, but quantum physics may help.
A year ago, New Scientist wrote about an algorithm that might allow future quantum computers to make a "Fourier transform" for pattern recognition. -If such quantum computers can ever become reality [with their massively parallel processing capacity], and fit into a robot that is resilient enough to adapt to damage, the we have literally a "killer application": tiny battlefield robots that can operate without supervision.
Twenty years ago, in the novel "Peace On Earth", Stanislaw Lem predicted that when small robots became smart and robust enough to operate on their own in the battlefield, it would have an effect similar to the stagnant battlefields of the first world war; conventional warfare would no longer be possible.
Assume the battlefield is full of small, self- repairing robots that can spot anything bigger than a bird or rodent moving about -it would no longer be possible to send tanks or even larger infantry units across without suffering devastating losses.
The reason sevicing missions to Hubble are so expensive is that NASA only has one manned spacecraft design: the expensive and not quite safe space shuttle.
The much cheaper Soyuz craft are usually launched from Kazakhstan, thus giving them the wrong *orbital inclination* for a rendezvous with Hubble, but the French launch site at Kourou has a R7/Soyuz-compatible launch pad under construction.
The reason the French are planning to use the Russian R 7 launcher is that the R 7 is extremely reliable, and as cheap per pound to orbit as the space shuttle.
If NASA could put pragmatism before prestige, Souyz missions to Hubble could be launched from Kourou at a fraction of the cost of launching the 2000-ton shuttle/solid fuel booster combination.
If it was necessary to add rockets to send Hubble into a higher "mothballing" orbit, a Progress capsule could be launched with the heavy load that could not be sent along with a Soyuz. This would take two R7 launches (one crewed Soyuz, one unmanned Progress) -still a trivial cost compared to a single shuttle launch.
Also, the Souyz is a thoroughly proven, simple and safe design, so the crew would not be in any danger.
The problem is not technology, but politics: The NASA administrators would rather let Hubble burn in the atmosphere than admit a 35-year old foreign design is better than the shuttle for the job.
Yours Birger Johansson
Alas, there is still a long way to go before space elevators can be built.
The strength of this material will be suffice for space "tethers" that can work as slings to catapult loads into higher orbits, or even give them escape velocity.
Genuine space elevators require a strength several orders of magnitude greater, but the maximum strength of individual nanotubes makes it theoretically possible to get there.
For details, see an article in American Scientist (NOT Scientific American) 5-7 years ago. It discussed the minimum strength required, and the reasons carbon nanotubes just might work.
Ironically, Buckminster Fuller, the discoverer of Buckminsterfullerene (carbon nanotubes can be seen as tubular extensions of these molecules), was a friend of Arthur C. Clarke, the author of the first space elevator novel "The Fountains of Paradise".
Neither Fuller nor Clarke suspected that Fuller's discovery one day might serve as the foundation to high-strenght materials that could make space elevators possible !
Yours Birger J.
I would love a genuine discovery of venusian life.... Unfortunately, Venus has a different, more violent form of tectonic resurfacing than the slow plate tectonics on Earth. Judging by the number of craters on the surface, the entire surface of Venus melted ca. 600 million years ago, as the build-up of internal heat made the crust crack up and hot magma totally covered the surface.
Even if life was present high up in the atmosphere, the heat of the ground was much higher than today, and would have been carried upwards, frying any airborne microbes.
Adiabatic cooling makes air cool with altitude, but to escape the heat of a molten-lava surface, any airborne life would have had to migrate up to altitudes with very thin air, much higher than the layer where the interesting molecules are found today.
While thick air might carry microbes, I do not see how life could survive and thrive in a stratospheric near-vacuum. Yours Birger J.
Although Sir Fred Hoyle proposed *complete* organisms might have developed in space, this is a partial vindication of his ideas.
He was sometimes ridiculed for some of his wilder ideas, which caused his more resonable ideas to be ignored; It is a pity he did not live a few additional months, to read this news.
One aspect other postings have neglected is the low probability a lone impactor should hit near a center of bronze-age civilization.
It is unlikely that the impactor was the only object, or even one of a few objects, involved in the impact; it was likely one of several fragments from a disrupted "rubble-pile" asteroid hitting the Earth.
Statistically, a meteorite is far more likely to hit the Pacific, or the Sahara than, say, New York or some other center of civilization.
Mesopotamia was one of the few centers of civilization of the period. If Mesopotamia was hit, it makes sense to assume that it was part of a "shotgun blast" of many impacts.
Some objects (like the precursor to comet SL-9 that hit Jupiter) are loosely bound "rubble piles" only held together by gravity.
If the impactor was a fragment of a loosely bound object, broken up by tidal forces during a previous near miss (like SL-9), it would have been a member of a swarm of objects hitting the Earth.
The probability that Mesopotamia would be hit was high, since the probability was high *everywhere*.
There might be many other impact sites buried under sediments around the world, or maybe most fragments were too small to survive atmospheric entry.
Most would have hit the ocean; if tsunami-generated deposits can be dated, it would be interesting to see if there is a cluster near 2300 B.C.