Actually, I was at that postdeadline session. I don't have the proceedings handy, but Lucent reported about the same capacity, something like 15 Tbps over 100 or 200 km (and another experiment with a few Tbps over 200 km, if memory serves). The previous record was set by Alcatel in 2002, transmitting 10.2 Tbps over 300 km, and I believe it still stands as the largest capacity*distance. The distance is important; I'm not sure that there haven't already been 100 Tbps transmissions over a few km -- much easier...
Before we intend to go to the moon there have to be a certain number of LEO flights to shake-down the system. It would be irresponsible to not include ISS capability during this phase.
Having ISS capability is nice, as long as it does not interfere with the main goal, namely operations beyond Earth orbit in a long-term program. Yet that is precisely what is happening. Did you read the mentioned whitepaper? NASA is pushing for CEV block 1 to be the Shuttle's replacement for personnel transportation to the ISS, and seeks to "minimize the gap" between Shuttle retirement and CEV qualification. This leads to short-term decisions, such as deleting methane-LOX engines (much better in the long term but too far off for ISS) or requiring the capability to use older-style docking equipment (because the ISS does not have a newer-style docking port).
NASA intends to purchase the "best value" for crew and cargo transportation services. If COTS comes through and is competitve then CEV flights will not be used for ISS resupply (at least not substantially).
This is the agency that killed the EELV-based CEV schemes. Remember, its predecessor, the OSP, was supposed to be light enough to be launched by heavy versions (or maybe even medium versions) of the Delta 4 and the Atlas 5. When it was clear that the Shuttle would be retired, they switched to a heavier CEV which needed a Shuttle-derived heavier launcher. This looks like a jobs program to me.
There also is the argument that man-rating the EELVs would be more difficult than starting from scratch. Yet, first, NASA did not make clear what would be required for man-rating a launcher; second, the Shuttle itself is not man-rated and less reliable than the Atlas family; third, the Ares I and V turn out not to be Shuttle-derived after all: new SRBs (5-segment), new ET (10-meter tank, incompatible with current tooling), new engines (RS-68 not man-rated, after all, and the J-2 has not been used for decades).
Seeing all this, it's an easy step to believe that even if COTS delivered, NASA would find an excuse to use its own products instead...
We can aerobrake to slow down a 2t probe from Mach 20 (I'm not sure the entry speed of the probes, this is just a guess. I don't think it will be slower than that)
More or less. The escape velocity for Mars is 5 km/s, so the probes from Earth hit the atmosphere slightly above that, about 5.5 km/s. That's 16-17 times the speed of sound at sea level on Earth (don't know the Mach number on Mars).
But to slow down a 200t spacecraft from that speed to Mach 1.0 is much more difficult. There is simply not enough air in the Mars atmosphere, especially in the upper atmosphere, which is where aerobraking takes place.
I see your point. Taking values from this NASA Web site, the terminal velocity for a 200-tonne object with a 100 m^2 cross-section (a heavy space shuttle) is still above 1 km/s at 5000 m altitude. I suppose you could use a retro-rocket for the last km/s (30-40% of the payload for fuel) then switch to a (large) parachute.
And you don't need a 200-tonne lander, anyway.:-)
Reverse rocket propulsion has worked on moon, but in order to do it on Mars, we need a whole lot more fuel. IIRC it's on the order of 5X the mass of your payload.
If you slow down from 5 km/s to 0, yes, that would be it. If you can shave 4 km/s off your entry velocity by aerobraking, that's much less.
The reverse propulsion problem is also compounded by the strong side wind.
You just have to thrust opposite to the airflow...
Now, I didn't say it was easy. Actually you convinced me that landing a 200-tonne behemoth on Mars is quite hard. But I don't think it's impossible with current technology, and I believe one can get away with a much lighter lander anyway, which would be easier. So, manned Mars missions should be possible in not too long a timeframe.
First off, it is completely unfair to compare COTS with CEV. CEV is being designed to support lunar and Mars missions. The delta-V, life support, habitable volume and TPS requirements are not even comparable to those for the COTS missions.
That's CEV block 2. Block 1 is aimed at the ISS; according to the whitepaper that the parent post cites, NASA's approach of developing the two as being based on the same vehicle is leading to a false sense of urgency and poor design decisions.
Second, COTS was underfunded on purpose. NASA wants out of the space transportation buisness and instead wants to be able to allocate its resources toward exploration while paying commercial providers for cheap, safe, reliable access to LEO.
Your point makes sense. However, if that's what NASA actually wanted, they wouldn't be developing a parallel infrastructure (CEV block 1 + CLV) to do the same. The message they are sending to the potential LEO service providers is not that NASA will be a customer. At best, a non-customer who has its own product; at worst, a competitor, and a subsidized competitor, at that.
As for more money risking to "addict" the industry to high budgets ("business as usual"), well, more money could be used to fund more competitors instead.
To land human on Mars, the current landing vehicles for MER and MSL are too small. We need to deliver at least 200t-300t's of payload.
Other have replied: with in-situ resource utilization, a lot can be saved on payload.
The atmosphere on Mars is too thin to use aero-braking, i.e. can't land like space shuttle on earth.
Do you mean aerobraking (which is quite possible, probes have done it) or horizontal landing (for which the atmosphere is indeed too thin, but a parachute can be used after aerobraking).
The Mars gravity is too great to have moon-like landing, i.e. reverse propulsion.
We've done it on Earth, why couldn't we on Mars? It would take more fuel than on the Moon, that's all.
Learn how to fly rockets backwards with sidewinds potentially 5x-10x stronger than that of Hurricane Katrina.
The atmosphere on Mars is thin. Do you really get hurricane-strength winds? (Strength, not speed.)
This phrase is in there twice" 1)"described by NASA's chief as "Apollo on steroids"" then later , 2) "in the words of NASA Administrator Michael Griffin, "Apollo on steroids.""
We have been to moon many times, since as long as 1969.
Six landings, from 1969 to 1972. That's not much, especially if one wants to set up a base there, and eventually colonies.
That place is not good for living! What is the timeline for Mars?
Mars isn't much better for living. More hydrogen available there, and it may be cheaper to go there in terms of delta-V if you use aerobraking on arrival. But it takes much longer, you can't phone home in real time, and the sky isn't as good as the Moon's for observatories.
Mars might be easier to terraform, but by the time this happens, I predict we'll have people on Mars and the Moon both.
the fact remains that it would have been much clearer from the beginning if they had just abbreviaed it Mass., which is the normally accepted abbreviation.
Seconded by a non-US resident, who may know the general location of Massachusetts but doesn't have a clue about all those two-letter abbreviations.
That would be why the latest mark of Soyuz (the TMA) has had serious problems on six out of eight flights to date.
Care to elaborate? I remember the first flight ending in a ballistic reentry, and maybe the fifth having problems during docking, but what about the others?
By pushing their new Meat In Space program, our government is once again pandering to jingoistic sentimentailty rather than the needs of hard science.
Manned spaceflight is not for science, it is for exploration and eventual colonization. You may equate that to "jingoistic sentimentality" but the need is there, and sending meat-based people to remote places is the goal per se.
And they will do science too, a lot of it--maybe less than what a same-budget unmanned program would have yielded in the short term, but it will also contribute to making it cheaper in the long run. Wasn't there a debate on this here a few days ago--which it seems I left dangling?
Well, it's refreshing to have a debate with real arguments, for a change, thanks... Even though I suspect we already agree on quite a few points.:-)
the "we should do it anyway" attitude comes down to convincing the government to increase the budget, which is separate from the best way of using it."
Well, yes, but note that you already use a premise about what 'the best way of using it' is.
I assumed that "the best way" was to make the most of a given budget, to do as much of "the stated goal" as possible. Then I tried to show that, whether this stated goal was space science or space colonization, you had to focus the effort you choose to spend on manned spaceflight on making it as economical as possible. Otherwise, for science, you end up doing less than what you could have done without humans on-site; and for colonization, you don't get a long-term commitment. Perhaps "self-sustaining" would be a better term than "economical".
Afterwards, differences in actions and decisions, as you say, stem from different estimations of how much and how fast the relative cost per capabilities of robots in space and humans in space will evolve. That's where you state that "if technology gets cheaper, it gets cheaper for robotic missions too", but it is not necessarily true. If launchers get cheaper, they do indeed for both ships and probes, but the cost of building and testing the probe becomes proportionately higher. If robotic technology becomes better and cheaper faster than launchers do, then you have a point. To be sure, I agree that robots are getting better and cheaper and will continue to do so, but some argue that we already have good enough technology right now, that the high launch costs are only a matter of flight rates. See for example A rocket a day. If that's true, then I see no point in funding NASA's missions as they are.
And even if robots remain forever a better science/cost proposition than humans, then it does not mean that one should send only robots into space; merely that science must not be the main justification for such a mission. Exploration and colonization should be. If you say you're doing it "for the science", scientists will argue that you'd do more of it with robots--as is now often heard. But then, you're absolutely right: if you do send a manned mission somewhere, just for the sake of it, you can probably include a scientist and instrument packages and do science as well. Not if it complicates said mission so much that it hampers the primary objective, mind you (no point in sending a dead scientist to Mars), but then it's "easier to train a scientist to pilot the spacecraft than to make a scientist out of a test-pilot astronaut"...
The extra costs of getting (and maintaining) a human in space is largely lacking on a base of Antartica. You have an breathable atmosphere, you have necessary resources (like water) in aboundance, you have normal gravity, you have the atmospheric shielding of our atmosphere, you don't have a need for a closed ecological system, food and supplies can be furnished regulary and relatively easily, etc.
It's not that different from e.g. Mars: there is water and carbon available there, gravity is over one third of Earth's (enough? Nobody knows one way or the other), enough atmosphere for meteorite and probably radiation shielding. And neither in Antarctica can you just step outside unprotected, nor get resupplied during the winter barring absolute emergency. Was it last year that there was the first medical evacuation ever in polar winter?
given the whims, if Nasa cuts their costs in half, it is not beyond possibility that politicians may decide to cut the budget in half because 'Nasa has shown it can do wha
I realize I mixed up arguments that should have remained separate, which led me to some poor reasoning. As you and another poster note, the "let's do it when it becomes affordable" argument is a false argument. However, I am in a "let's focus on making it affordable so we can do more of it" mindset.
What I should have said is this. First, if the taxpayers are prepared to set aside a fixed amount of money for spaceflight, then you have to take the economic point of view in order to make the most of what you have; the "we should do it anyway" attitude comes down to convincing the government to increase the budget, which is separate from the best way of using it. If the stated goal is to do science, and robots give you more science on a given budget than people, then you should send robots--possibly many robots. However, if you believe that someday it will be cheaper to send people (more on that below), you may invest some of the money on manned spaceflight--but not to have people do the same kind of science as the robots could do! Fly them to find a way to bring down manned spaceflight costs.
Second, if the stated goal includes colonization, then sending only robots does not make much sense. You have to send people, taking a long-term approach. While this may interest more taxpayers so that they give you a higher budget, you still have to find a way to make it as economical as possible, so as to minimize your dependence on changing political whims--as happened with the Apollo program. And if you make manned spaceflight economical, then you may as well send scientists along to do science. So this also means bringing down manned spaceflight costs.
Third, it seems that the biggest government space agency worldwide, NASA, isn't focused on either goal. It is not pursuing science, since it is cutting both space probes and human spaceflight science, to cover the expense of developing the CEV and new launchers. And it is not trying to make spaceflight economical: one, after they retire the Shuttle, they aim for the same operations budget (not including Moon missions) for a lesser LEO capability (can't find a reference, sorry); two, the GAO believes that the project isn't soundly managed and there will be cost overruns; three, the SFF believes that they're making the same mistakes as with the Shuttle, with a one-vehicle-fits-all approch and an artificial urgency to minimize the "gap" during which the USA won't have an operational manned spaceflight capability.
Meanwhile, several companies are trying to lower launch costs and leverage the space tourism market, but their business case is harder to make as long as NASA is a possible competitor--and a subsidized one, at that. If NASA were a customer instead, then the private sector would have an easier job and they want to bring down the cost of manned spaceflight. So one can't rely exclusively on them to do exploration, all right, but government-sponsored space organizations have been at it for decades and haven't made a significant advance in over thirty years. Perhaps the profit-seekers should be given a chance then?
Now, to answer some of your points:
it will always be far more expensive to send humans then robots, nomatter how cheap things get.
I'm not sure about that. Is it now cheaper to send a person or a robot to do some work in Antarctica? After all, an autonomous robot has to be very sophisticated; it may well become cheaper to send a man, including his life support equipment, than to build and test a robot on the complexity level e.g. of the current Mars rovers.
Probably there will be some kind of expanding frontier: when tourists can buy cheap tickets to space hotels in Earth orbit, big entities (be it NASA, National Geographic or Bill Gates) will be able to afford to go to the Moon or Mars, though se
We all heard the reasoning for abolishing space-exploration (particulary human-based) before, and I think the major flaw in all these 'arguments' why we shouldn't go into space is that they always set economic factors as a premise.
Some opponents of human space exploration set science as the major interest, and go on to say that much more science can be done by robots, costs being equal.
Anyway, many (most?) people agree that one should not necessarily limit oneself to economically viable things, and that it is desirable for mankind to colonize space, there is disagreement on the price that should be paid for that endeavor.
Especially if you believe that manned spaceflight can be made affordable and therefore economically viable (if only for space tourism).
When it is affordable, colonization and exploration will be much cheaper and not depend on multi-decade internationally state-sponsored efforts. This will be much easier, and more exploration (and science too) will be done with less taxpayer money. After all, Columbus would not have been granted all the funding necessary for a huge research effort into creating shipbuilding technology; he was given a couple of standard-technology ships.
Now, add to the mix that the massive investment of NASA credits into making expensive launchers is an economic deterrent for the development of cheaper launchers, and you can well conclude that supporting space exploration implies opposing existing space agencies...;-)
Why in the heck would we be launching a stationary lander when the Spirit and Opportunity have been roving the surface for over 2 years?
Because they don't have the money for sending new rovers, but they do have enough to launch the old spare of the one that crashed on Mars last decade due to insufficient testing.
When Bush announced manned spaceflight to the Moon and Mars, Slashdotters broadly supported it (perhaps someone can find the original post). But of course, there are not unlimited resources, so money must be diverted from something else, namely science.
Yes and no. NASA seemed to think it could implement Bush's Vision for Space Exploration with only moderate budget increases, by redirecting funds from the Shuttle infrastructure. This turned out not to be the case, so they're cutting science.
Now, the Space Frontier Foundation believes that NASA is not implementing the VSE: it specified that NASA should focus on going back beyond the ISS and low Earth orbit, leaving exploitation of the latter to private enterprise and buying services as needed. (Some might say that private enterprise is not there yet, thinking Scaled Composites or Armadillo, but I'm sure Boeing and Lockheed are quite capable of developing something. Just make sure competitors can bid every few years...) Yet NASA is spending most of its energy developing the CEV block 1, which it says is urgent because it must replace the Shuttle as soon as practical. And this urgency justifies poor design decisions which will hamper it if it is to be used beyond LEO as well (CEV block 2).
So the SFF's recommandation is:
explicitly forbid NASA to develop a new vehicle not destined to go beyond LEO, and reassign CEV block 1 funding e.g. to the science programs which were cut;
since replacing the Shuttle wouldn't be directly NASA's role any longer, urgency vanishes, and CEV block 2 design can be reconsidered, as well as the decision not go with new Shuttle-derived launchers which at this point don't have much in common with the Shuttle any more.
Erm, you still have to get the fuel up there right?.. and the cost of putting something up there is still reasonably proportional to weight?
True, it doesn't save money in the short run. But even if all that fuel still comes from Earth, it lowers the minimum mass per launch. So you can use many light boosters to supply the fuel depot instead of a few heavy ones. Some people believe that the current high cost of launches is due to a low launch rate (maybe only 10-20 a year, worldwide), and increasing that rate would help lower this cost. See e.g. a rocket a day.
To be sure, I believe this is a single-wavelength transmission record. For WDM (multiwavelength), I believe Alcatel's 2002 record of 10 Tbps over 3 x 100 km still hasn't been topped (Frignac et al, OFC 2002).
Now, an intercontinental journey is easier than going to orbit, but according to calculations I had made some time ago, it's not that easy, maybe 3-4 km/s to cross several thousand kilometers.
To follow up on my own post, here are the actual results. The required speed v for a minimum-energy ballistic trajectory crossing distance d, with R and g being Earth's radius and surface gravity (6400 km and 9.8 m/s^2), v1 being orbital speed at altitude 0 (v1=sqrt(Rg)=7.9 km/s), and letting x=d/(2R) one has:
v = v1 * sqrt{2 * [ sin(x) - (sin(x))^2 ] / (cos(x))^2 ]}
v ~ sqrt(gd) for shorter distances (less than 2000 km)
This yields 7.5 km/s for 12000 km (Los Angeles-Sydney), almost orbital speed, or 4.5 km/s just for 2500 km (Los Angeles-New York).
Re:Forgive me if this is a stupid question...
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Space Race 2.0 has Begun
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· Score: 3, Informative
Would it be possible to use suborbital craft such as this as a means to provide rapid transportation between distant terrestrial locations?
Yes and no. It is quite possible, but you'd need quite a lot bigger vehicles, more like current rockets.
To see this, you have to understand that the biggest obstacle is speed: to just reach 100 km altitude, as these spacecraft do, you need to launch at a speed of about 1 km/s. Orbital speed (low Earth orbit) is 8 km/s. Unfortunately, it's not a question of eight times more fuel, it's exponential; if your propulsion system is such that for each ton of payload you must expend another ton of propellant, total mass 2 tons, then you need 2^8-1=255 tons of propellant to go to orbit.
Now, an intercontinental journey is easier than going to orbit, but according to calculations I had made some time ago, it's not that easy, maybe 3-4 km/s to cross several thousand kilometers. SpaceShipOne definitely couldn't make it.
So, yes, this is possible and perhaps interesting--if you don't mind the acceleration, as another poster said--but it is significantly harder than what is currently being done by private spaceflight companies. Which does not mean it's forever impossible, of course, nor that private companies won't make orbit or beyond eventually...
I thought Voyagers and the Pioneer probes were leaving the Sun system. If NH is faster, then shouldn't it also be leaving the Sun's pull?
I think it will, thanks to the Jupiter gravity assist. I'm not quite sure that right now, fast-and-fastest as it is, New Horizons actually has the kinetic energy to leave the solar system on its own: although I read its heliocentric Earth-escape velocity was 28.8 mi/s, which translates to 46.3 km/s, higher than heliocentric escape (42 km/s), I also read that it was departing Earth at 10.1 mi/s, or 16.1 km/s, which yields a geocentric Earth-escape velocity of sqrt(16.1^2 - 11^2) = 11.8 km/s, therefore a maximal heliocentric Earth-escape velocity around 41-42 km/s. Possibly less depending on where it is headed.
in 26 years New Horizons will surpass Voyager I as the most distant human made object.
Apparently,
someone disagrees.
According to his “crude calculations”, New Horizons will not overtake the Voyagers.
I don't know which of you is right, and I admit I won't take the time to research enough data to scribble on an envelope of my own, but doesn't this depend a lot from the exact launch date? Perhaps the two-day delay changed the actual result?
Diode lasers use silicon, or at least compounds of silicon.
Actually, the first article you cite only mentions silicon carbide as a substrate, that is, what to grow the active material on (gallium nitride in this case); silicon is not involved in the laser emission.
The second article is a bit misleading, in that it mentions silicon to illustrate what a semiconductor is, without insisting on the fact that silicon is not a good light emitter due to its indirect bandgap.
At least, that is, under normal conditions; the original article authors' idea is to use a holey silicon device, where the band structure is presumably altered.
NASA, if very, very cagey can do what they want on a pittance, letting people knock each other over trying to do for piddly prizes.
Actually, with adequate funding, this could be a nice incentive. As Henry Spencer said:
As I've noted before, if the government wants to put Americans back on the Moon and is willing to spend (say) ten billion to make it happen, much the most effective way is to simply announce that the next hundred Americans to walk on the Moon will each be given $100M. It will be the biggest stampede you've ever seen, and nobody will have to "oversee" anybody.
More mundanely, consider having NASA announce that starting in 2010, each year it will buy 20 round-trip tickets to the Moon from the lowest bidder, bids not to exceed $50M/ticket. If concerned about safety, stipulate that each year, one of those tickets will be used to fly a randomly-selected senior executive of the spaceline, refusal being grounds for cancellation
of the contract.
Re:I like it, but I also have questions and doubts
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NASA's New Shuttle
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Well, on Soyuz. On a man-rated Soyuz, which hasn't had an accident in a long time.
Yes, and was developed a long time ago too, and flies often because it has a lot in common with the unmanned Molniya.
Cynically, a rocket developed in a non-commercially oriented socialist environment beats them all on market these days.
Actually, NASA has been called the most socialist agency in the US government (see e.g. here, here, or here).
One could say that a socialist centrally-planned development plan is more efficient in the short run (and NASA's goal was to beat the Russians fast) but much worse on the long run (and NASA is struggling to do as well as in the 1960s, while the Russian space agency has become much more aggressive, capitalist-like, and operates on a shoestring budget...)
Slashdot Mirror
Memory serves, fingers don't. I meant a few Tbps over 2000 km.
Actually, I was at that postdeadline session. I don't have the proceedings handy, but Lucent reported about the same capacity, something like 15 Tbps over 100 or 200 km (and another experiment with a few Tbps over 200 km, if memory serves). The previous record was set by Alcatel in 2002, transmitting 10.2 Tbps over 300 km, and I believe it still stands as the largest capacity*distance. The distance is important; I'm not sure that there haven't already been 100 Tbps transmissions over a few km -- much easier...
Having ISS capability is nice, as long as it does not interfere with the main goal, namely operations beyond Earth orbit in a long-term program. Yet that is precisely what is happening. Did you read the mentioned whitepaper? NASA is pushing for CEV block 1 to be the Shuttle's replacement for personnel transportation to the ISS, and seeks to "minimize the gap" between Shuttle retirement and CEV qualification. This leads to short-term decisions, such as deleting methane-LOX engines (much better in the long term but too far off for ISS) or requiring the capability to use older-style docking equipment (because the ISS does not have a newer-style docking port).
This is the agency that killed the EELV-based CEV schemes. Remember, its predecessor, the OSP, was supposed to be light enough to be launched by heavy versions (or maybe even medium versions) of the Delta 4 and the Atlas 5. When it was clear that the Shuttle would be retired, they switched to a heavier CEV which needed a Shuttle-derived heavier launcher. This looks like a jobs program to me.
There also is the argument that man-rating the EELVs would be more difficult than starting from scratch. Yet, first, NASA did not make clear what would be required for man-rating a launcher; second, the Shuttle itself is not man-rated and less reliable than the Atlas family; third, the Ares I and V turn out not to be Shuttle-derived after all: new SRBs (5-segment), new ET (10-meter tank, incompatible with current tooling), new engines (RS-68 not man-rated, after all, and the J-2 has not been used for decades).
Seeing all this, it's an easy step to believe that even if COTS delivered, NASA would find an excuse to use its own products instead...
More or less. The escape velocity for Mars is 5 km/s, so the probes from Earth hit the atmosphere slightly above that, about 5.5 km/s. That's 16-17 times the speed of sound at sea level on Earth (don't know the Mach number on Mars).
I see your point. Taking values from this NASA Web site, the terminal velocity for a 200-tonne object with a 100 m^2 cross-section (a heavy space shuttle) is still above 1 km/s at 5000 m altitude. I suppose you could use a retro-rocket for the last km/s (30-40% of the payload for fuel) then switch to a (large) parachute.
And you don't need a 200-tonne lander, anyway. :-)
If you slow down from 5 km/s to 0, yes, that would be it. If you can shave 4 km/s off your entry velocity by aerobraking, that's much less.
You just have to thrust opposite to the airflow...
Now, I didn't say it was easy. Actually you convinced me that landing a 200-tonne behemoth on Mars is quite hard. But I don't think it's impossible with current technology, and I believe one can get away with a much lighter lander anyway, which would be easier. So, manned Mars missions should be possible in not too long a timeframe.
That's CEV block 2. Block 1 is aimed at the ISS; according to the whitepaper that the parent post cites, NASA's approach of developing the two as being based on the same vehicle is leading to a false sense of urgency and poor design decisions.
Your point makes sense. However, if that's what NASA actually wanted, they wouldn't be developing a parallel infrastructure (CEV block 1 + CLV) to do the same. The message they are sending to the potential LEO service providers is not that NASA will be a customer. At best, a non-customer who has its own product; at worst, a competitor, and a subsidized competitor, at that.
As for more money risking to "addict" the industry to high budgets ("business as usual"), well, more money could be used to fund more competitors instead.
Other have replied: with in-situ resource utilization, a lot can be saved on payload.
Do you mean aerobraking (which is quite possible, probes have done it) or horizontal landing (for which the atmosphere is indeed too thin, but a parachute can be used after aerobraking).
We've done it on Earth, why couldn't we on Mars? It would take more fuel than on the Moon, that's all.
The atmosphere on Mars is thin. Do you really get hurricane-strength winds? (Strength, not speed.)
I don't see the problem; Griffin actually said it. Google should get many references; searching only on NASA-affiliated Web sites, see e.g.:t egory=Video g ies/2005CHRONO.PDF
http://www.jpl.nasa.gov/multimedia/index.cfm?MMCa
http://www-lib.ksc.nasa.gov/lib/archives/chronolo
Six landings, from 1969 to 1972. That's not much, especially if one wants to set up a base there, and eventually colonies.
Mars isn't much better for living. More hydrogen available there, and it may be cheaper to go there in terms of delta-V if you use aerobraking on arrival. But it takes much longer, you can't phone home in real time, and the sky isn't as good as the Moon's for observatories.
Mars might be easier to terraform, but by the time this happens, I predict we'll have people on Mars and the Moon both.
Seconded by a non-US resident, who may know the general location of Massachusetts but doesn't have a clue about all those two-letter abbreviations.
Care to elaborate? I remember the first flight ending in a ballistic reentry, and maybe the fifth having problems during docking, but what about the others?
Manned spaceflight is not for science, it is for exploration and eventual colonization. You may equate that to "jingoistic sentimentality" but the need is there, and sending meat-based people to remote places is the goal per se.
And they will do science too, a lot of it--maybe less than what a same-budget unmanned program would have yielded in the short term, but it will also contribute to making it cheaper in the long run. Wasn't there a debate on this here a few days ago--which it seems I left dangling?
Well, it's refreshing to have a debate with real arguments, for a change, thanks... Even though I suspect we already agree on quite a few points. :-)
I assumed that "the best way" was to make the most of a given budget, to do as much of "the stated goal" as possible. Then I tried to show that, whether this stated goal was space science or space colonization, you had to focus the effort you choose to spend on manned spaceflight on making it as economical as possible. Otherwise, for science, you end up doing less than what you could have done without humans on-site; and for colonization, you don't get a long-term commitment. Perhaps "self-sustaining" would be a better term than "economical".
Afterwards, differences in actions and decisions, as you say, stem from different estimations of how much and how fast the relative cost per capabilities of robots in space and humans in space will evolve. That's where you state that "if technology gets cheaper, it gets cheaper for robotic missions too", but it is not necessarily true. If launchers get cheaper, they do indeed for both ships and probes, but the cost of building and testing the probe becomes proportionately higher. If robotic technology becomes better and cheaper faster than launchers do, then you have a point. To be sure, I agree that robots are getting better and cheaper and will continue to do so, but some argue that we already have good enough technology right now, that the high launch costs are only a matter of flight rates. See for example A rocket a day. If that's true, then I see no point in funding NASA's missions as they are.
And even if robots remain forever a better science/cost proposition than humans, then it does not mean that one should send only robots into space; merely that science must not be the main justification for such a mission. Exploration and colonization should be. If you say you're doing it "for the science", scientists will argue that you'd do more of it with robots--as is now often heard. But then, you're absolutely right: if you do send a manned mission somewhere, just for the sake of it, you can probably include a scientist and instrument packages and do science as well. Not if it complicates said mission so much that it hampers the primary objective, mind you (no point in sending a dead scientist to Mars), but then it's "easier to train a scientist to pilot the spacecraft than to make a scientist out of a test-pilot astronaut"...
It's not that different from e.g. Mars: there is water and carbon available there, gravity is over one third of Earth's (enough? Nobody knows one way or the other), enough atmosphere for meteorite and probably radiation shielding. And neither in Antarctica can you just step outside unprotected, nor get resupplied during the winter barring absolute emergency. Was it last year that there was the first medical evacuation ever in polar winter?
I realize I mixed up arguments that should have remained separate, which led me to some poor reasoning. As you and another poster note, the "let's do it when it becomes affordable" argument is a false argument. However, I am in a "let's focus on making it affordable so we can do more of it" mindset.
What I should have said is this. First, if the taxpayers are prepared to set aside a fixed amount of money for spaceflight, then you have to take the economic point of view in order to make the most of what you have; the "we should do it anyway" attitude comes down to convincing the government to increase the budget, which is separate from the best way of using it. If the stated goal is to do science, and robots give you more science on a given budget than people, then you should send robots--possibly many robots. However, if you believe that someday it will be cheaper to send people (more on that below), you may invest some of the money on manned spaceflight--but not to have people do the same kind of science as the robots could do! Fly them to find a way to bring down manned spaceflight costs.
Second, if the stated goal includes colonization, then sending only robots does not make much sense. You have to send people, taking a long-term approach. While this may interest more taxpayers so that they give you a higher budget, you still have to find a way to make it as economical as possible, so as to minimize your dependence on changing political whims--as happened with the Apollo program. And if you make manned spaceflight economical, then you may as well send scientists along to do science. So this also means bringing down manned spaceflight costs.
Third, it seems that the biggest government space agency worldwide, NASA, isn't focused on either goal. It is not pursuing science, since it is cutting both space probes and human spaceflight science, to cover the expense of developing the CEV and new launchers. And it is not trying to make spaceflight economical: one, after they retire the Shuttle, they aim for the same operations budget (not including Moon missions) for a lesser LEO capability (can't find a reference, sorry); two, the GAO believes that the project isn't soundly managed and there will be cost overruns; three, the SFF believes that they're making the same mistakes as with the Shuttle, with a one-vehicle-fits-all approch and an artificial urgency to minimize the "gap" during which the USA won't have an operational manned spaceflight capability.
Meanwhile, several companies are trying to lower launch costs and leverage the space tourism market, but their business case is harder to make as long as NASA is a possible competitor--and a subsidized one, at that. If NASA were a customer instead, then the private sector would have an easier job and they want to bring down the cost of manned spaceflight. So one can't rely exclusively on them to do exploration, all right, but government-sponsored space organizations have been at it for decades and haven't made a significant advance in over thirty years. Perhaps the profit-seekers should be given a chance then?
Now, to answer some of your points:
I'm not sure about that. Is it now cheaper to send a person or a robot to do some work in Antarctica? After all, an autonomous robot has to be very sophisticated; it may well become cheaper to send a man, including his life support equipment, than to build and test a robot on the complexity level e.g. of the current Mars rovers.
Probably there will be some kind of expanding frontier: when tourists can buy cheap tickets to space hotels in Earth orbit, big entities (be it NASA, National Geographic or Bill Gates) will be able to afford to go to the Moon or Mars, though se
Some opponents of human space exploration set science as the major interest, and go on to say that much more science can be done by robots, costs being equal.
Anyway, many (most?) people agree that one should not necessarily limit oneself to economically viable things, and that it is desirable for mankind to colonize space, there is disagreement on the price that should be paid for that endeavor. Especially if you believe that manned spaceflight can be made affordable and therefore economically viable (if only for space tourism).
When it is affordable, colonization and exploration will be much cheaper and not depend on multi-decade internationally state-sponsored efforts. This will be much easier, and more exploration (and science too) will be done with less taxpayer money. After all, Columbus would not have been granted all the funding necessary for a huge research effort into creating shipbuilding technology; he was given a couple of standard-technology ships.
Now, add to the mix that the massive investment of NASA credits into making expensive launchers is an economic deterrent for the development of cheaper launchers, and you can well conclude that supporting space exploration implies opposing existing space agencies... ;-)
Because they don't have the money for sending new rovers, but they do have enough to launch the old spare of the one that crashed on Mars last decade due to insufficient testing.
Yes and no. NASA seemed to think it could implement Bush's Vision for Space Exploration with only moderate budget increases, by redirecting funds from the Shuttle infrastructure. This turned out not to be the case, so they're cutting science.
Now, the Space Frontier Foundation believes that NASA is not implementing the VSE: it specified that NASA should focus on going back beyond the ISS and low Earth orbit, leaving exploitation of the latter to private enterprise and buying services as needed. (Some might say that private enterprise is not there yet, thinking Scaled Composites or Armadillo, but I'm sure Boeing and Lockheed are quite capable of developing something. Just make sure competitors can bid every few years...) Yet NASA is spending most of its energy developing the CEV block 1, which it says is urgent because it must replace the Shuttle as soon as practical. And this urgency justifies poor design decisions which will hamper it if it is to be used beyond LEO as well (CEV block 2).
So the SFF's recommandation is:
True, it doesn't save money in the short run. But even if all that fuel still comes from Earth, it lowers the minimum mass per launch. So you can use many light boosters to supply the fuel depot instead of a few heavy ones. Some people believe that the current high cost of launches is due to a low launch rate (maybe only 10-20 a year, worldwide), and increasing that rate would help lower this cost. See e.g. a rocket a day.
To be sure, I believe this is a single-wavelength transmission record. For WDM (multiwavelength), I believe Alcatel's 2002 record of 10 Tbps over 3 x 100 km still hasn't been topped (Frignac et al, OFC 2002).
To follow up on my own post, here are the actual results. The required speed v for a minimum-energy ballistic trajectory crossing distance d, with R and g being Earth's radius and surface gravity (6400 km and 9.8 m/s^2), v1 being orbital speed at altitude 0 (v1=sqrt(Rg)=7.9 km/s), and letting x=d/(2R) one has:
v = v1 * sqrt{2 * [ sin(x) - (sin(x))^2 ] / (cos(x))^2 ]}
v ~ sqrt(gd) for shorter distances (less than 2000 km)
This yields 7.5 km/s for 12000 km (Los Angeles-Sydney), almost orbital speed, or 4.5 km/s just for 2500 km (Los Angeles-New York).
Yes and no. It is quite possible, but you'd need quite a lot bigger vehicles, more like current rockets.
To see this, you have to understand that the biggest obstacle is speed: to just reach 100 km altitude, as these spacecraft do, you need to launch at a speed of about 1 km/s. Orbital speed (low Earth orbit) is 8 km/s. Unfortunately, it's not a question of eight times more fuel, it's exponential; if your propulsion system is such that for each ton of payload you must expend another ton of propellant, total mass 2 tons, then you need 2^8-1=255 tons of propellant to go to orbit.
Now, an intercontinental journey is easier than going to orbit, but according to calculations I had made some time ago, it's not that easy, maybe 3-4 km/s to cross several thousand kilometers. SpaceShipOne definitely couldn't make it.
So, yes, this is possible and perhaps interesting--if you don't mind the acceleration, as another poster said--but it is significantly harder than what is currently being done by private spaceflight companies. Which does not mean it's forever impossible, of course, nor that private companies won't make orbit or beyond eventually...
I think it will, thanks to the Jupiter gravity assist. I'm not quite sure that right now, fast-and-fastest as it is, New Horizons actually has the kinetic energy to leave the solar system on its own: although I read its heliocentric Earth-escape velocity was 28.8 mi/s, which translates to 46.3 km/s, higher than heliocentric escape (42 km/s), I also read that it was departing Earth at 10.1 mi/s, or 16.1 km/s, which yields a geocentric Earth-escape velocity of sqrt(16.1^2 - 11^2) = 11.8 km/s, therefore a maximal heliocentric Earth-escape velocity around 41-42 km/s. Possibly less depending on where it is headed.
Anybody has more precise figures?
Apparently, someone disagrees. According to his “crude calculations”, New Horizons will not overtake the Voyagers.
I don't know which of you is right, and I admit I won't take the time to research enough data to scribble on an envelope of my own, but doesn't this depend a lot from the exact launch date? Perhaps the two-day delay changed the actual result?
Actually, the first article you cite only mentions silicon carbide as a substrate, that is, what to grow the active material on (gallium nitride in this case); silicon is not involved in the laser emission. The second article is a bit misleading, in that it mentions silicon to illustrate what a semiconductor is, without insisting on the fact that silicon is not a good light emitter due to its indirect bandgap.
At least, that is, under normal conditions; the original article authors' idea is to use a holey silicon device, where the band structure is presumably altered.
Actually, with adequate funding, this could be a nice incentive. As Henry Spencer said:
Yes, and was developed a long time ago too, and flies often because it has a lot in common with the unmanned Molniya.
Actually, NASA has been called the most socialist agency in the US government (see e.g. here, here, or here).
One could say that a socialist centrally-planned development plan is more efficient in the short run (and NASA's goal was to beat the Russians fast) but much worse on the long run (and NASA is struggling to do as well as in the 1960s, while the Russian space agency has become much more aggressive, capitalist-like, and operates on a shoestring budget...)