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RobS - your concerns are well founded. I've been looking for some sort of numbers for the Moon-Mars L1 shunt and haven't been able to get any. One big advantage is that very small Delta V allows you to do a low speed Mars surface landing without having to expend delta V on Mars orbital insertion or aerobraking. the 3.8 km/s assumes an aerobraking maneuver which is dangerous in the Martian atmosphere with the variable density of the atmosphere and even more dangerous with large loads. A direct insertion burn is much preferrable and would add considerably to the total mission delta V. the 0-energy trajectory should be safer and allow you to stay < 3.5 km/s. OTOH, the orbital trajectories are going to be much more stringent, relying upon chaos effects.
Also, if we set up some sort of lunar L1 space station, we can refuel spacecraft there and have the ability to send mass to both Mars and the Moon with the same starting location. The moon is particularly accesible from L1. Every point on the moon is accessible with minimal delta V in under 12 hours from L1. That would allow the use f space tugs to carry freight to L1, lowering the fuel requirements for the spacecraft and greatly lightening the HLV cargo capacity requirements.
I've been too busy to E-mail the originating professor. I think that that's the way to go, though. It looks as if he's at least run some rough numbers on the subject.
By vertical launches, I assume you mean railguns? And I also assume that you're including the horizontal velocity component necessary to achieve a stable orbit?
If you can get a sufficiently powerful railgun to work reliably, it would be the 1st choice. However, to my knowledge railguns are still fairly unreliable, have low lifetimes and can't impart much energy to a projectile, limiting you to very small payloads.
The rotating sling idea can handle fairly large payloads and can be built with existing materials and theoretical materials which are likely to be constructed in the next 20 years. Plus, the lifetime of such a device should be nearly infinite.
I think that Titan is much ore practical in terms of terraforming than Venus. :;):
It's always easier to deal with too cold than too hot. Of course, the big problem is that you are only getting about 1% of the sunlight that we see here on Earth. I doubt that we can ever get shirt sleeve conditions with any existing tech but iot could be made more hospitable. For one thing, we could import O2 or crack it from the rocks below and burn some of those hydrocarbon seas to get CO2 into the atmosphere. With some CFCs, you could probably bring the surface temperature up some tens of degrees. Orbital mirros would help but not enough to get a meaningful change in temp - sunlight at that distance is just too small. The best bet would be to generate heat on the surface. If there's He3, fusion generators could dump massive amounts of waste heat into the enviroment. Also, you could set up huge rotating tether systems to generate electrical power in the Saturn magnetic field. The result would be ample power to power light sources or other means to send power to Titan.
Ummmm, you do realize that Jupiter's escape velocity is about 60 km/s right? That's a biiig gravity well to climb out of. To be able to slingshot Jupiter, the probe velocity in Jupiter's upper atmosphere is going to have to be something like 65-70 km/s. I've got serious doubts that any real material can withstand any sort of prolonged contact with gass at those velocities. In order to collect any significant amount of material, you've got to skim at least deep enough to start hitting the low end of the molecular flow regime of pressure. I don't know how to calculate the aerodynamic heating and ion erosion of materials at those speeds but it's going to be ugly.
OTOH, once you get enough H2 into the atmosphere, random lightning shold cause the reaction 2H2+CO2->2H2O+C to proceed spontaneously via combustion. OTOH, I'm not sure how well the reaction will proceed at Venutian temperatures and pressures. Regardless, the remaining problem is that you now havea runaway greenhouse system with H2O rather than CO2 as the primary heat retainer. How exactly do we plan to deal with the 100+ atmospheres of H2O vapor? Not to mention the fact that the planet's albedo is approximately 0 because of all the precipitated carbon.
Personally, I'm kind of happy about the way this has played out as well. The Air Force has plenty of cash - let them shoulder some of the burden of developing technology they wil no doubt end up using.
RobS - go to the zero energy trajectories thread. There's more info there. It's got nothing to do with wormholes. It uses the equivalent potential energy of the lagrange points to largely eliminate the energy of transfering between planets. Basically, the Trans Mars injection burn and MArtian orbital injection burn are eliminated. This probably saves a km/s of delta V. Since the relationship between total delta V and fuel mass fraction is an exponential one, the savings are quite large. I've been estimating a 30% increase in Martian payload using chemical thrusters. If you've got a way to get to lunar L1 via space tug or other low or 0 cost means, your Mars payload goes up by at least a factor of 2.
Gennaro - to answer your older post:
I'd like to keep the L1 gatway in mind at least. Let's not rely upon it but make sure to do rough mass fraction calculations for our cargo transport technologies to see how applicable it is. From what I can tell, the 0-energy trajectories save about 1km/s at the expense of a longer travel time. For chemical NTR and ion engines, I think that there is a significant benefit. for GCNR, there's probably no point.
I agree that something like a GCNR for fast transit would be great for human flights. However, if we get teh technology perfected, there's no reason to not use it for all our missions. The high Isp means that your fuel expenses are minimal. You could send crew via high-speed flat trajectories and cargo standard high speed Hohmann trajectories.
I think that the Mars SSTo would have to be sent as a kit or lander or something. The facilites to build such a craft on Mars won't exists for a long time.
I'm interested to see how this turns out. We'll find out soon enough, the launch occurs at 1PM PST.
There was a Slashdot thread about this. It turns out that calling this a 'moon' is really stretching the definition. It's going to be something like 4.5 million miles away at the closest.
On the other hand, I found out that our moon isn't actually a moon! It turns out that the Moon actually feels a stronger gravitation attraction to the Sun than the Earth. As a result, the Earth and Moon are more accurately described as a binary planet.
Well, speaking as a scientist, I've seen the whole gamut in scientists. You have close-minded people who reject anything they didn't read in a textbook (these people make good technicians but not much else), average people and wide-eyed dreamers that spend too much time looking at the clouds.
Scientists tend to be sceptical on average because of the nature of the job. Science is one of the few professions where it is expected that most of the stuff you do will fail. A scientist that never has a failed experiment is not pushing the boundaries hard enough. As a result, scientists become very adept at throwing out information. If you can't be sceptical, you will never do well as a scientist - you'll always be spending your time chasing 'phenomenon' that are nothing more than random variations or instrument glitches. As a result, scientists tend to appy the same viewpoint to the rest fo the world.
When done in moderation, this is a very good way to approach the world, when done in excess, you tend to get close-mindedness.
Hmmm, I'm not sure how much in the way of polls you're going to get here - it's much more of a motivated bunch of amateurs here rather than anything organized. Perhaps someone that follows polls more closely than I do might be able to help. We've had polls on the boards but I wouldn't call them scientific or statistically reliable by any stretch of the imagination.
As for facts, do keep in mind that anything you get from here is going to be biased. There's a pro-Mars exploration (duh!) bias here and quite a bit of anti-NASA sentiment. I think that this is fairly common amongst amateur space buffs. This is largely due to the perception that NASA, while still doing some really great work, has largely been taken over by politicians. The result is that vast sums of money have been squandered on projects that never get completed. We managed to get to the moon in 1969 and now, 30+ years later, don't even have the capability to go back there anymore.
The only really handy simgle reference I would point you towards is Robert Zubrin's The Case for Mars. It's written by an aerospace engineer that used to work with NASA. It details a plan to get to Mars in 10 years for $30-40 billion. His plan, called Mars Direct was largely responsible for changing the whole direction of NASA's MArs exploration plans. Of course, reading a 300+ page book for your paper might not prove practical.
I'd recommend Googling and reading some of the threads here. There is a tremendous amount of stuff out on the Web critiquing NASA with figures and facts. However, to summarize what you'll find out there: The Space Shuttle was a poorly designed vehicle that has never lived up to its promise of a cheap, reusable launch vehicle. The International Space Station is nothing more than an orbital money pit. The ISS is basically $25 billion of military welfare to keep Russian rocket scientists employed so they don't work on 3rd world missile systems and to justify the continuation of the Shuttle program. The scientific benefits have been and will be approximately zilch - something confirmed by an NSF study about 3-4 years ago.
On the other hand NASA's unmanned space program of probes and rovers has been quite successful and produced large amounts of good data of ther last several decades. The Hubble, Gallileo, the Mars rovers (all 3), the Mars orbiters, Magellan, and a host of other lower profile missions have all worked wonderfully.
The general consensus of why NASA's manned space program has failed so badly is that is lack focus and has become home to many intra-agency factions that are all trying to get a larger piece of the funding. As a result, every new Shuttle replacement or Mars/moon program gets all these hangers-on that start adding non-essential baggage and requirements to it so that their program looks more important and gets more money. The result is a series of failed programs that have gotten bloated and unusable.
What NASA needs is a clearly defined direction and narrow focus so that the money is spent on clearly defined programs. Whether Bush's new space initiative is the correct way to go is up to debate. However, I think that most of the people here would agree that the mandate to return to the Moon is a waste of time and money.
Yeah, Mars is a lot more forgiving for SSTOs. As it is, they're barely possible on this planet. Of course, advances in artificial diamond manufacturing could change this. There's some academic research (and some commerical as well) that can grow perfect single crystal diamonds at about 0.1mm/hour. Given enough money, we could actually grow industrial sized diamonds. Diaomnd is brittle but very strong and has the highest heat conduction capacity of any know material. There has got to be an application for something like that for SSTOs.
On the other side, though, Martian SSTOs won't be able to be retrofitted and maintained as well. Here on Earth, we've got entire aerospace companies that can give an SSTO a once over when it lands. On Mars, at least fora few decades, your repair and maintainance will be very rudimentary. As a result, your SSTO design will have to be MUCH more robust and therefore lower performance.
Also, don't forget, lasers are very inefficient. For standard solid phase and gas phase lasers like ruby or neon, about 0.1% of your input energy goes to making light. The rest gets bled off as heat. A 40 Watt Argon ion laser requires a 720 volt, 50 amp dedicated power circuit and a water cooling system. Modern diode pumped solid state lasers can manage to get an efficiency up in the 10% range but that's about as good as its going to get.
Waht I think that most people forget is that commercial airplanes these days basically fly themselves. The pilot is responsible for taxiing and taking off. Everything else is handled by the autopilot unless something goes wrong. I think that the only reason to have a pilot is to load and unload cargo. Even that can be largely circumvented by using standardized cargo loading/unloading proceedures that are compatible with automated pilots. If you launch several SSTOs, perhaps one could be piloted and that pilot could be up there to manually take control of any other craft if the need arose.
The finding of fossils or life on Mars would definately make the Drake equation more favorable but not in a terribly helpful way. The problem with the Drake equation is that almost all of the numbers in it are unknown. Unfortunately, the only way to start filling in the numbers is to actually observe large numbers of other solar systems and find extra-terrestrial life and catalog it.
For example, before, we had absolutely no good way to know how common life was on other planets. If we find fossils or life on Mars, it's clear that life is possible on other planets but we still don't know how common it is. This is because it's a single example and its impossible to extrapolate anything meaningful about it.
For example, lets say that you live in a neighborhood. However, for whatever reason, you can't leave your house. You want to try and estimate how common other people living around you are. So, you send a robotic probe to the neighbor's house. Inside, noone's living there but there are clear signs that someone was living there at some time in the past.
Now, you have got a map of the city so you know how many roads there are. nfortunately, the map doesn't show houses. You can't actually see the other streets so you don't know if there are actually houses on those streets. Furthermore, even if there are buildings, you don't know if people live in them.
Before, you had no idea of people lived in those buildings but seemed likely. Now, you do know that it is possible but still have no good idea how many of them there are.
What we need for the Drake equation to be even remotely useful:
1: orbital telescopes capable of actually imaging earth-sized planets in nearby star systems.
2: a better understanding of how life evolved on this planet.
3: a better understanding of how solar systems form
4: a better understanding of how our galaxy formed
5: a better understanding of how human intelligence works and the probability of it evolving
6: a better understanding of how often intelligent creatures develop a technological society that wil try and communicate with us.
IIRC, the Soviets had quite a bit of experience in building liquid sodium cooled reactors for their attack submarines. Perhaps NASA could get some of their expertise on the cheap.
One thing I've always wondered about is why you don't use thermocouples to get some power out of the radiators? My understanding isthat RTGs use the thermal gradient between the core and the radiator to generate electrical power. It seems like a good way to maximize the power coupling efficiency.
[I read through the second paper and although I don't understand all the terminology (what's C3?) I think I got the general gist. This isn't the low energy trajectory in use. They're using Mars' L1 and L2 to hold communication satellites. They use a low Mars flyby in combo with a braking maneuver to lower the fuel consumption. The principles they use for this braking maneuver are the same ones used on the low energy trajectory and demonstrate its usefulness. However, they are getting there through standard orbital mechanics.
There's 2 kinds of night vision technology. The most common one is light amplification - it takes the low levels of light present at night and amplifies it so that you can see. This doesn't work in complete darkness like Europa's oceans since there's no light to amplify. (or shouldn't be - maybe you could use the natives' casino neon signs for a light source)
The other is less used because it's a bit bulky - IR imaging. This looks at heat radiation. However, the problem is that you need heat sources to see anything. Since everything in the ocean is going to be about the same temperature, you won't be able to amke anything out in IR other than what the average temperature is. Hot sea vents and living organisms will show up very well but overall sonar is the best means of seeing underwater.
I agree that humanity reduced (ironically) through technology to its most base biological imperatives is a very dark future. However, I can't help but think that the aesthetic and emotional concerns that we have a biological creatures will be lost as we move further away from out biological roots.
We've got a discussion devoted to these low energy trajectories in a new thread. For the purposes of this thread, let's just assume that these trajectories are potentially possible and work on more mundane stuff like engine technologies. If it turns out that low energy trajectories are possible, we can just use the estimates in this thread that rely upon them, otherwise we use the more consevative estimates.
OK, let's take stock of what we've got so far:
chemical, NTR, ion, GCNR and possibly ETP. I'm open to the other technologies like NSWR but I think that they just really don't fit into this particular discussion.
We've largely dismissed ion engines but how well do they perform on the way to Mars? Let's assume that in 15 years, we have ion thrusters capable of 6000 Isp and a thrust of 20 N (when the engines are used in clusters). While it's true that high thrust engines allow shorter thrust times, if we're in the context of a 6 month Mars transit, do ion engines catch up? Assuming a nuclear power source (let's ignore the difficulties in a 100kW+ nuclear reactor for now) and a 100 MT spaceship that is doing a 4.5 km/s delta V to Mars. You get the necessary deltaV in 260 days of solid thrusting. That requires a fuel fraction of 8%. Of course, orbits will have to be modified to accomodate the gradual velocity gain but I think that it's fairly clear that next gen ion engine clusters have great potential.
I checked my calculations and can't find a problem - could someone check them for me? I want to make sure I did them correctly.
I think that overall idea is old but that the computational means to actual realize them is very recent.
Check [http://groups.msn.com/DaveDietzler/thel1gateway.msnw]it out! A nice summary page.
Heres some info from there about getting from LEO to lunar L1:
Delta V from 200 km LEO to lunar L1 - 3116 m/s + 50m/s stabilization burn at L1.
Delta V from 500 km LEO to lunar L1 - 3042 m/s + 50-100 m/s burn.
travel time: 4 days.
travel time with NEP: 6-7 days?! (I'd like to confirm this number, it seems very low)
Delta V from lunar L1 to earth L1 or L2: 50 m/s
LEO to Mars could therefore require a total delta V of something like 3.5 km/s of delta V. That's a full 1km/s we don't have to spend. Furthermore, the fuel/mass ratio is exponential so that going from a 4.5 km/s to 3.5 km/s Mars transit and a 450 Isp H2O2 engine would bring our non-fuel fraction of the spacecraft from 36.1% to 45.2% or a 25% increase in usable cargo. Alternately, you can view it as effective increase in engine Isp from 450 to 580
From everything that I know about the subject (the links you gave above pretty much encompass all I know), you are correct. The hard part is getting to lunar L1 if you are going to Mars. Coming back, the hard part is getting to Martian L1. Everything else, including going from Martian L1 to Mars/LMO and from lunar L1 to Earth or LEO is basically free.
IMO, the most interesting thing about Genesis is the trajectory. Honestly the composition of the solar wind is sort of interesting but I think that we've gota pretty good idea what is is already. The demonstration of the low energy trajectories is invaluable, though.
I love how the 48 hour course correction is the ONLY major thrusting they have to do aside from station keeping and a couple of minor mid-course corrections. Basically, one thrust is enough to go from LEO to Earth L1, sit there for a 2.5 years, loop back past Earth L2 and land in Utah.
With this technology, getting from any lunar or Earth L point is a matter of delta Vs in terms of m/s, not km/s.
I or someone here needs to contact MArtin Lo and find out from him if any serious work has been done to look at Earth Mars trajectoreis and if we might be able to help out by donating computing power.
I suspect high resolution sonar would be used for wide area photos and that a flash camera would be used for close-up shots of things of interest.
It could have been millions of years - I don't know. It imght be possible to find out but AFAIK, research on these critters is pretty low key with few people in the field. There's entire branches of life on this planet with only a handful of underfunded researchers devoted to them.
The simplest explanation is that these were originally protozoan with little to no organelles (many organisms in this phyla don't have things like mitochondria and golgi bodes.) At some point they somehow entered into a beneficial relationship with bacteria that could do things like digest cellulose. Over time, the two orgamisms evolve so that they are dependent upon each other. Many archaeprotista die if you use antibiotics to kill the bacterial symbionts.
Most of out own organelles like mitochondria, golgi bodies, nuclei and chloroplasts (in plants) are believed to have come from a similar mechanism. What's unclear is if these archaeprtosta are simply more recent symbiotes or actually an unchanged variant of the original eukaryotic reatures from 1-2 billion years ago that all higher life came from.