I'm having trouble parsing what you wrote. You seem to be talking about autonomous navigation at the beginning of the sentence but are describing something flatly contradictory with the concept of autonomous navigation by the end.
And for the record, by and large, air traffic does go in straight lines (or more accurately, great circles). There's some diversion (occasionally large, but generally small) for weather, and of course on approach you need specific vectors, but by and large it's "from point A to point B". Separation is preferentially handled by time and altitude rather than lat/lon separation.
Hyperloop Alpha is two seats side by side (2x14 seating), so I'm not sure what you're talking about. And that's for the smaller, passengers-only variant. They didn't list seating arrangements for the "passengers + vehicles" variant, but given the size increase it's probably at least three abreast.
Standardized cars will go over with the market about as well as standardized housing has. Actually worse because the needs for different types of cars are vastly varied; there's a huge amount of car form that follows intended function. An economy box is not a sports car is not an offroader is not a pickup truck is not a luxury SUV is not a courier van.... (on and on and on). Every usage intent has serious repercussions across the vehicle.
I remember proposing quadcopter flying vehicles with computer-controlled balance between each prop's thrust to a pilot friend when I was a teenager. My friend laughed at me like I was an idiot, saying you'd never be able to achieve stability on something like that.
I still smile a bit whenever I see a quadcopter because of that conversation;)
Actually, I've come around to view them as kind of inevitable.
1) There is a strong push, and will continue to be, from delivery services for permitting delivery drones. Bit by bit, they'll get it.
2) The economic case will keep causing them to push for a permitting process for larger and larger drones. Bit by bit, step by step, they'll get it.
3) Once you start having drone payloads in the hundreds of kilograms range, people are seriously going to start asking "Why can't you haul people with these?" And then will come all of the financially interested parties pushing, bit by bit, for permission to do so.
That said, this concept ticks all of the wrong boxes.
1) Quadcopter style = inefficient in flight. Even small scale delivery drones are moving away from it. It's fine for toys and little video cameras, but not for scale delivery with any sort of significant crossrange requirements.
2) Requires everyone standardize their cars to a particular drone. Not going to happen.
3) Requires everyone standardize their cars to a particular chassis, and more to the point bans monocoque. Not going to happen.
4) Requires everyone to use other peoples' chassis. Regardless of their condition. Without even knowing what condition they're going to be in.
5) Requires at least one spare chassis be at the destination when you get there. Something complicated by the fact that people can change their mind (or be forced to divert), throwing off estimates of what will be at a location at a given point in time. But at its most fundamental level, constraining people to much more limited destinations.
6) Requires such an integral vehicle connection - the body and chassis - be done in some "rapidly and automatically removable" fashion. Same with the critical connection with the props (albeit with lower mass loadings)
7) Doubles up powertrains. I hope you think battery packs are cheap, because this proposed system means (if done electrically) that you have to have two of them per vehicle, assuming an average of one "drone" in operation per "car". I'm assuming that you're leaving the battery pack behind, since that's a heavy element. Of course, that means when you get to the destination, you're using someone else's battery pack as well.
No, I'm not a fan.
ask yourself why don't we all already have a self-flying helicopter.
Drone helicopters exist. Are you talking about "at scale"? Because scaling up relatively new technology doesn't appear the instant you snap your fingers.
A better question is "why doesn't everyone fly around in helicopters?" in general. And the answers are pilot skill, noise, space requirements, safety, regulations, and cost (including insurance / liability, and the fact that the fuel is very expensive). These are in general, however, interconnected problems and with technological solutions at varying stages of maturity. It's clearly a barrier at present, but I hardly see it as a limitless one. Large, yes, but not unbounded. IMHO, electric is a big potential boon toward scaledown, at least where short flight times are required, as electric motors can be made small, light, and reliable, with very high power densities (making redundancy easier as well), plus they run on dirt-cheap "fuel". Battery mass is a big problem on long flights, but not short.
BTW, helicopters aren't that much less efficient than cars. A 4-passenger helicopter may get ~7 mpg (40 l/100km). But it goes in straight lines and doesn't wait in traffic.
Yep. The force on it will be incredible, especially once they start getting toward their maximum (700m) depth. But it's that same incredible force that lets them store so much power in such a small volume. Plus, concrete is cheap.
They are storing water by pumping it uphill. It's just that the bottom of their hill is up to 700 meters below sea level.
It's actually a very clever idea. Power is stored right at the place of generation (no expensive transmission infrastructure for the excess power), and 700 meters is a huge amount of head; you'll never get even close to comparable to that on land. And you don't ruin any countryside or face NIMBY opposition, either (reservoirs are big and disruptive - even for pumped hydro).
To have three days of pumped storage sufficient to provide for the energy needs of the US, we'd need to flood 1/3rd of the continental United States
These are not based on compressed air. The turbines pump water and generate power from water. The system would work just as well if they were making a vacuum in the spheres (excepting the fact that water isn't stable in a vacuum and will vaporize;) ).
What they have is sort of a weird variant on a pumped hydroelectric dam. The amount of air and effects of compression / expansion thereof have little significance versus the pressure of the water.
I expect quantum computing would be like battery improvements: something people continue to complain about being hype, even while at the same time it migrates into their everyday lives without them noticing. I mainly expect that should quantum computing chips make their way into consumer processors, your average programmer would never touch them - but backend system library calls that they make would increasingly use them without the frontend developer ever being aware.
Its hard to say, because you can't directly translate conventional algorithms to quantum ones, and it's hard to say what processes will readily find a home in quantum computing vs. which ones won't. But if quantum chips were "commonplace", you can bet that any CPU intensive tasks today (graphics, neutral nets, physics simulation, etc) would seek to find ways to offload as much effort to quantum algorithms as possible, where they can be found. Some tasks, such as searching unordered datasets or doing Foureir transforms for image / sound compression, already have fast quantum algorithms.
Yeah, NASA has always been terrible at public outreach. Anyone ever seen the NASA TV channel? Just terrible. There's no excitement in anything they make for the public, despite the fact that they're working in one of the most exciting fields out there. Contrast with what SpaceX does, where each launch is almost like a sporting event, with "newscasters" and "commentators", screaming crowds, HD footage from multiple angles, etc. That's PR. And I doubt they're spending a fortune to do so, versus what everything else costs in rocketry.
Perhaps the most exciting thing NASA does is their press conferences to announce findings (say, post-flyby preliminary results and the like). But I think only space geeks like myself can get excited about a NASA press conference.
Some parts of the US federal government are good at PR: The military is an obvious one - they work closely with TV and movie producers to get them enthusiastic and supportive. They manage it top to bottom, wanting to see whole scripts in advance to make sure that they portray the military in a good light - and if they do, they get access to locations, hardware, troops, gear, almost anything. They even require producers to have a minder.... er... I'm sorry, "technical adviser", who follows them around and (strike)makes sure they make it positive like they promised(/strike)offers "helpful advice". It's a sleek operation of mutual exploitation, where the military gets free PR and recruiting, and the movie makers get taxpayer-funded hardware, locations and manpower.
Not that NASA should go that far. But they should do a lot better than something with the quality of a late-night public access TV channel. They have amazing facilities, settings and people, and are doing exciting things. They should modernize their PR.
The thing is, this is already default for NASA. NASA is far more open than ESA. They public domain everything they can, and are much more open about releasing raw data, sooner. ESA is the one that really needs to get past its closed culture.
I'm not quite getting the point of this "release", since I use a number of pieces of NASA software and have always been able to get what I need. I guess they're just taking down the request forms or something? The real problem IMHO has never been "getting it", it's been "getting it to work". They make some very neat things, but they have such small user bases that they're not well refined, and getting them to work on your platform or finding quality documentation can be a pain.
The auto industry in general is terrible for women. I once ran a small console software supplier for the auto industry. I think my attitude toward the industry is best summed up by the time when (at a meeting with major figures of a major auto maker) my sales rep privately informed me that they're skipping the third step of how they usually make deals, on account of me. The first step being discussing the project over a ridiculous-priced dinner. The second step being discussing it at the bar. The third step - skipped - being discussing it at a strip club.
I had previously heard rumours of stuff like this, such as a HR rep at a startup automaker complaining to me that their sales rep was submitting strip club receipts for reimbursement as business expenses. But I got to see the culture firsthand.
So when I hear about this sort of stuff at Tesla, I'm not surprised. Sad - I'd like to hope that they'd have a different culture, since they're trying to make a different kind of car - but not surprised.
I can just imagine some rogue programmer installing the following on it:
1) As big of a battery pack as it can carry as "payload", strapped to its back. 2) Facial recognition software that measures the number of and distance to any people recorded by its camera 3) Modern neural net, trained by being rewarded when the actions it takes lead to 1) it approaching other people, and 2) people fleeing from it.
Another option apart from orbit is going to L2 and back, if they want to basically "hover" with the moon blocking the Earth, right on the cusp of drifting away from the Earth-Moon system and into a free orbit around the sun. They'd be the first people ever to go there. It's 3.5km/s outbound, 0.6km/s back. Or if they want a long-duration stay (~100d) they can get back by the interplay of the Sun-Earth-Moon system for only 0.1 km/s (in the process going way far away from Earth).. There's probably some such returns with intermediary dV and durations as well.
But obviously a free return trajectory is the lowest energy. If I recall correctly Apollo's burn was ~3.2 km/s
That's an old graphic, but yes, we have an excellent artist aboard. Of course, they mostly want to go for what looks the most aesthetically pleasing, while I'm always niggling on the technical details;) The conversations usually go like,
"But.... you can't have people living there, the ballonets are going to expand into that when they launch the ascent stage... either the ballonets are going to dramatically expand or the habitat is going to dramatically collapse, take your pick. And if you store the ascent stage that close, it's going to destroy the whole habitat if there's a mishap while it's fueled. And how can I possibly fit all of that floor area into the fairing? Plus I don't see any scrubber for ISRU... it's going to need to be big, I'm struggling to get the absorption figures to work for sufficient resource collection with a 4.2 meter prop.....";) But really, so long as their final graphics don't end up with a giant pirate flag or anything like that, I'm sure we can deal with a bit of "artistic license":)...
Oh wait a minute, I just noticed your username. Geoffrey.landis? As in, the Geoffrey Landis? Oh wow, hey, we should chat some time.;) (bare minimum, I at least need to ask for permission to reproduce some figures from a few of your papers). If you get a chance, definitely drop me a line at mQeme@eaQku.neQt (remove Qs to despammify). I actually just dropped by Slashdot as a break in the middle of working on some graphics illustrating non-Hohmann transfer times vs. delta-V between Earth, Mars and Venus, demonstrating the advantage Venus has due to the Oberth effect;)
1) It's about 7% of what NYC consumes, not 10%. NYC being only a tiny fraction of total US demand, which is in turn just a fraction of world demand. Global electricity production averages around 15 TW.
500MW is a moderate sized power plant. Not even a large one. It's nothing that impressive. Cost of such a plant is 500M-$1,5B, which is nothing by rocketry standards.
2) That's not 500MW to stand idle; that's 500MW to launch 175 tonnes per day. That's 68.5kWh per kilogram. $7 of electricity per kilogram. Oooh, what a terrible waste of power.
3) If that's too much, the larger version uses significantly less per kilogram.
Is there some reason to get so much mass out of this gravity well
Do you seriously have to ask what sort of market there would be for ~$800 tickets to orbit? I'm sorry, but we're not talking "for the wealthy", we're talking for everyone at those prices.
I mentioned that. The discoveries on lunar water are in consistent (for example, non-detection by Kaguya, disputed detection by Deep impact, criticism of Chandrayaan's detection as not being consistent with solid ice (at best small ice particles), etc. But I do agree that on the balance the evidence is pretty compelling that there are places where ice could be recovered/produced. Even if you take the optimistic view on volatiles (not just water), they're clearly not evenly spread, and generally seem to be (as expected) at significant driving distances from lit regions. Workable? Probably. Ideal? Not really. But hey, it's certainly a better outlook than it was a couple decades ago:) I'll be a lot happier though when we have some ground truth on the subject showing CHONPS all in the same general area;)
Hey, we're thinking along parallel lines!!
I'm part of a group called Venus Labs that's actually developing the concept further, doing more detailed studies on each component of the concept that Landis presented.:)
Not exactly. Minimum energy trajectories are really undesirable for humans. Fine for cargo, but you get a lot of time cut off the trip with just a relatively small amount of extra delta-V. Seriously, I recommend running out the numbers for fast Hohmann transfers to Mars - assuming aerocapture, it's a major improvement at little cost.
SpaceX, for one, wants fast transits with ITS. And I don't blame them.
Slashdot Mirror
I'm having trouble parsing what you wrote. You seem to be talking about autonomous navigation at the beginning of the sentence but are describing something flatly contradictory with the concept of autonomous navigation by the end.
And for the record, by and large, air traffic does go in straight lines (or more accurately, great circles). There's some diversion (occasionally large, but generally small) for weather, and of course on approach you need specific vectors, but by and large it's "from point A to point B". Separation is preferentially handled by time and altitude rather than lat/lon separation.
Hyperloop Alpha is two seats side by side (2x14 seating), so I'm not sure what you're talking about. And that's for the smaller, passengers-only variant. They didn't list seating arrangements for the "passengers + vehicles" variant, but given the size increase it's probably at least three abreast.
Standardized cars will go over with the market about as well as standardized housing has. Actually worse because the needs for different types of cars are vastly varied; there's a huge amount of car form that follows intended function. An economy box is not a sports car is not an offroader is not a pickup truck is not a luxury SUV is not a courier van.... (on and on and on). Every usage intent has serious repercussions across the vehicle.
I remember proposing quadcopter flying vehicles with computer-controlled balance between each prop's thrust to a pilot friend when I was a teenager. My friend laughed at me like I was an idiot, saying you'd never be able to achieve stability on something like that.
I still smile a bit whenever I see a quadcopter because of that conversation ;)
Actually, I've come around to view them as kind of inevitable.
1) There is a strong push, and will continue to be, from delivery services for permitting delivery drones. Bit by bit, they'll get it.
2) The economic case will keep causing them to push for a permitting process for larger and larger drones. Bit by bit, step by step, they'll get it.
3) Once you start having drone payloads in the hundreds of kilograms range, people are seriously going to start asking "Why can't you haul people with these?" And then will come all of the financially interested parties pushing, bit by bit, for permission to do so.
That said, this concept ticks all of the wrong boxes.
1) Quadcopter style = inefficient in flight. Even small scale delivery drones are moving away from it. It's fine for toys and little video cameras, but not for scale delivery with any sort of significant crossrange requirements.
2) Requires everyone standardize their cars to a particular drone. Not going to happen.
3) Requires everyone standardize their cars to a particular chassis, and more to the point bans monocoque. Not going to happen.
4) Requires everyone to use other peoples' chassis. Regardless of their condition. Without even knowing what condition they're going to be in.
5) Requires at least one spare chassis be at the destination when you get there. Something complicated by the fact that people can change their mind (or be forced to divert), throwing off estimates of what will be at a location at a given point in time. But at its most fundamental level, constraining people to much more limited destinations.
6) Requires such an integral vehicle connection - the body and chassis - be done in some "rapidly and automatically removable" fashion. Same with the critical connection with the props (albeit with lower mass loadings)
7) Doubles up powertrains. I hope you think battery packs are cheap, because this proposed system means (if done electrically) that you have to have two of them per vehicle, assuming an average of one "drone" in operation per "car". I'm assuming that you're leaving the battery pack behind, since that's a heavy element. Of course, that means when you get to the destination, you're using someone else's battery pack as well.
No, I'm not a fan.
Drone helicopters exist. Are you talking about "at scale"? Because scaling up relatively new technology doesn't appear the instant you snap your fingers.
A better question is "why doesn't everyone fly around in helicopters?" in general. And the answers are pilot skill, noise, space requirements, safety, regulations, and cost (including insurance / liability, and the fact that the fuel is very expensive). These are in general, however, interconnected problems and with technological solutions at varying stages of maturity. It's clearly a barrier at present, but I hardly see it as a limitless one. Large, yes, but not unbounded. IMHO, electric is a big potential boon toward scaledown, at least where short flight times are required, as electric motors can be made small, light, and reliable, with very high power densities (making redundancy easier as well), plus they run on dirt-cheap "fuel". Battery mass is a big problem on long flights, but not short.
BTW, helicopters aren't that much less efficient than cars. A 4-passenger helicopter may get ~7 mpg (40 l/100km). But it goes in straight lines and doesn't wait in traffic.
The coming dystopia is going to be awesome.
Yep. The force on it will be incredible, especially once they start getting toward their maximum (700m) depth. But it's that same incredible force that lets them store so much power in such a small volume. Plus, concrete is cheap.
You're probably thinking of compressed air where there's loss of compression heat. 80-85% is not unreasonable for an incompressible fluid like water.
They are storing water by pumping it uphill. It's just that the bottom of their hill is up to 700 meters below sea level.
It's actually a very clever idea. Power is stored right at the place of generation (no expensive transmission infrastructure for the excess power), and 700 meters is a huge amount of head; you'll never get even close to comparable to that on land. And you don't ruin any countryside or face NIMBY opposition, either (reservoirs are big and disruptive - even for pumped hydro).
That's utter nonsense.
These are not based on compressed air. The turbines pump water and generate power from water. The system would work just as well if they were making a vacuum in the spheres (excepting the fact that water isn't stable in a vacuum and will vaporize ;) ).
What they have is sort of a weird variant on a pumped hydroelectric dam. The amount of air and effects of compression / expansion thereof have little significance versus the pressure of the water.
I expect quantum computing would be like battery improvements: something people continue to complain about being hype, even while at the same time it migrates into their everyday lives without them noticing. I mainly expect that should quantum computing chips make their way into consumer processors, your average programmer would never touch them - but backend system library calls that they make would increasingly use them without the frontend developer ever being aware.
Its hard to say, because you can't directly translate conventional algorithms to quantum ones, and it's hard to say what processes will readily find a home in quantum computing vs. which ones won't. But if quantum chips were "commonplace", you can bet that any CPU intensive tasks today (graphics, neutral nets, physics simulation, etc) would seek to find ways to offload as much effort to quantum algorithms as possible, where they can be found. Some tasks, such as searching unordered datasets or doing Foureir transforms for image / sound compression, already have fast quantum algorithms.
Yeah, NASA has always been terrible at public outreach. Anyone ever seen the NASA TV channel? Just terrible. There's no excitement in anything they make for the public, despite the fact that they're working in one of the most exciting fields out there. Contrast with what SpaceX does, where each launch is almost like a sporting event, with "newscasters" and "commentators", screaming crowds, HD footage from multiple angles, etc. That's PR. And I doubt they're spending a fortune to do so, versus what everything else costs in rocketry.
Perhaps the most exciting thing NASA does is their press conferences to announce findings (say, post-flyby preliminary results and the like). But I think only space geeks like myself can get excited about a NASA press conference.
Some parts of the US federal government are good at PR: The military is an obvious one - they work closely with TV and movie producers to get them enthusiastic and supportive. They manage it top to bottom, wanting to see whole scripts in advance to make sure that they portray the military in a good light - and if they do, they get access to locations, hardware, troops, gear, almost anything. They even require producers to have a minder.... er... I'm sorry, "technical adviser", who follows them around and (strike)makes sure they make it positive like they promised(/strike)offers "helpful advice". It's a sleek operation of mutual exploitation, where the military gets free PR and recruiting, and the movie makers get taxpayer-funded hardware, locations and manpower.
Not that NASA should go that far. But they should do a lot better than something with the quality of a late-night public access TV channel. They have amazing facilities, settings and people, and are doing exciting things. They should modernize their PR.
The thing is, this is already default for NASA. NASA is far more open than ESA. They public domain everything they can, and are much more open about releasing raw data, sooner. ESA is the one that really needs to get past its closed culture.
I'm not quite getting the point of this "release", since I use a number of pieces of NASA software and have always been able to get what I need. I guess they're just taking down the request forms or something? The real problem IMHO has never been "getting it", it's been "getting it to work". They make some very neat things, but they have such small user bases that they're not well refined, and getting them to work on your platform or finding quality documentation can be a pain.
That would be hilarious telling him that someone assumed that he was a feminist ;)
When was the last time you've met with top executives as an OEM to discuss a purchase?
Call BS all you want. But that's the way it actually is.
The auto industry in general is terrible for women. I once ran a small console software supplier for the auto industry. I think my attitude toward the industry is best summed up by the time when (at a meeting with major figures of a major auto maker) my sales rep privately informed me that they're skipping the third step of how they usually make deals, on account of me. The first step being discussing the project over a ridiculous-priced dinner. The second step being discussing it at the bar. The third step - skipped - being discussing it at a strip club.
I had previously heard rumours of stuff like this, such as a HR rep at a startup automaker complaining to me that their sales rep was submitting strip club receipts for reimbursement as business expenses. But I got to see the culture firsthand.
So when I hear about this sort of stuff at Tesla, I'm not surprised. Sad - I'd like to hope that they'd have a different culture, since they're trying to make a different kind of car - but not surprised.
I can just imagine some rogue programmer installing the following on it:
1) As big of a battery pack as it can carry as "payload", strapped to its back.
2) Facial recognition software that measures the number of and distance to any people recorded by its camera
3) Modern neural net, trained by being rewarded when the actions it takes lead to 1) it approaching other people, and 2) people fleeing from it.
' ... and then setting it loose in the streets.
I love living in the future. ;)
Another option apart from orbit is going to L2 and back, if they want to basically "hover" with the moon blocking the Earth, right on the cusp of drifting away from the Earth-Moon system and into a free orbit around the sun. They'd be the first people ever to go there. It's 3.5km/s outbound, 0.6km/s back. Or if they want a long-duration stay (~100d) they can get back by the interplay of the Sun-Earth-Moon system for only 0.1 km/s (in the process going way far away from Earth).. There's probably some such returns with intermediary dV and durations as well.
But obviously a free return trajectory is the lowest energy. If I recall correctly Apollo's burn was ~3.2 km/s
That's an old graphic, but yes, we have an excellent artist aboard. Of course, they mostly want to go for what looks the most aesthetically pleasing, while I'm always niggling on the technical details ;) The conversations usually go like,
"But.... you can't have people living there, the ballonets are going to expand into that when they launch the ascent stage... either the ballonets are going to dramatically expand or the habitat is going to dramatically collapse, take your pick. And if you store the ascent stage that close, it's going to destroy the whole habitat if there's a mishap while it's fueled. And how can I possibly fit all of that floor area into the fairing? Plus I don't see any scrubber for ISRU... it's going to need to be big, I'm struggling to get the absorption figures to work for sufficient resource collection with a 4.2 meter prop....." ;) But really, so long as their final graphics don't end up with a giant pirate flag or anything like that, I'm sure we can deal with a bit of "artistic license" :)...
Oh wait a minute, I just noticed your username. Geoffrey.landis? As in, the Geoffrey Landis? Oh wow, hey, we should chat some time. ;) (bare minimum, I at least need to ask for permission to reproduce some figures from a few of your papers). If you get a chance, definitely drop me a line at mQeme@eaQku.neQt (remove Qs to despammify). I actually just dropped by Slashdot as a break in the middle of working on some graphics illustrating non-Hohmann transfer times vs. delta-V between Earth, Mars and Venus, demonstrating the advantage Venus has due to the Oberth effect ;)
1) It's about 7% of what NYC consumes, not 10%. NYC being only a tiny fraction of total US demand, which is in turn just a fraction of world demand. Global electricity production averages around 15 TW.
500MW is a moderate sized power plant. Not even a large one. It's nothing that impressive. Cost of such a plant is 500M-$1,5B, which is nothing by rocketry standards.
2) That's not 500MW to stand idle; that's 500MW to launch 175 tonnes per day. That's 68.5kWh per kilogram. $7 of electricity per kilogram. Oooh, what a terrible waste of power.
3) If that's too much, the larger version uses significantly less per kilogram.
Do you seriously have to ask what sort of market there would be for ~$800 tickets to orbit? I'm sorry, but we're not talking "for the wealthy", we're talking for everyone at those prices.
Reaction Control System.
I mentioned that. The discoveries on lunar water are in consistent (for example, non-detection by Kaguya, disputed detection by Deep impact, criticism of Chandrayaan's detection as not being consistent with solid ice (at best small ice particles), etc. But I do agree that on the balance the evidence is pretty compelling that there are places where ice could be recovered/produced. Even if you take the optimistic view on volatiles (not just water), they're clearly not evenly spread, and generally seem to be (as expected) at significant driving distances from lit regions. Workable? Probably. Ideal? Not really. But hey, it's certainly a better outlook than it was a couple decades ago :) I'll be a lot happier though when we have some ground truth on the subject showing CHONPS all in the same general area ;)
I'm part of a group called Venus Labs that's actually developing the concept further, doing more detailed studies on each component of the concept that Landis presented. :)
Not exactly. Minimum energy trajectories are really undesirable for humans. Fine for cargo, but you get a lot of time cut off the trip with just a relatively small amount of extra delta-V. Seriously, I recommend running out the numbers for fast Hohmann transfers to Mars - assuming aerocapture, it's a major improvement at little cost.
SpaceX, for one, wants fast transits with ITS. And I don't blame them.