I'd go for Robert Zubrin's Athena double fly by. It's more realistic than Dennis Tito's Inspiration Mars because it doesn't require the flyby of Venus on the way back.
Though Inspiration Mars shortens the total flight for Inspiration Mars to 500 days instead of 700, it does it by increasing the speed with which it hits the Earth system on the way back making it far harder to slow down when it gets back to Earth. That was one of the details that got turned up as his idea was discussed by experts after he announced it. And they also get such a short time at Mars.
I'm not sure they would bother to set it up with teleoperation capabilities for such a short visit to Mars, I mean even an hour or so would be worth doing, but - no mention of such things in the plan. Is just the aim to fire a human couple, confined in a tiny space together, physically, around Mars, I don't really get it as a concept. Sort of human cannonball - I got really interested when it was first announced but as the details became clearer I couldn't see the point.
If we are at a level of technology where we have to go for 500 days because the crew will die in a mission of 700 days, I think we are steering so close to the wind that we shouldn't attempt it at all.
And the Athena double fly by gives far more science return. And because it doesn't depend on a Venus flyby, you can do it every two years. And - don't see that it's going to be that significantly more expensive.
To review how it works - the first flyby puts the spacecraft into an orbit similar to that of Mars. Second flyby of Mars, half a Mars year later (one Earth year later) then puts it into a return trajectory to Earth.
And - after first flyby, because it goes into an orbit very similar to Mars - then the crew remain close to Mars for a long time, so you get a lot of time for fairly close teleoperation of vehicles on the surface.
So long as it is combined with spacecraft sent to the surface for the crew to operate -and surely other projects and countries would collaborate sending missions to he surface for them to control given the huge advantage of close up telepresence operation - then it would probably do as much in a few hours as other missions have done in years.
So - I vote for the double Athena flyby. Similar cost to the Inspiration Mars but better conceived.
Then after that I'd vote for the Herro plan which puts a human mission into a sun synchronous Molniya orbit around Mars - pretty much continuous tele-operation of rovers on the surface of Mars.
The advantage of the double Athena - like Inspiration Mars - is that it is a "free return" trajectory, only need fine adjustments through the entire program. So might be first.
But the HERRO - just takes you to a Mars capture orbit. And it does have some advantages for safety also. I wonder - what about sending a preliminary mission first to its intended orbit with fuel, food etc for the human crew? So before you set off, you know that you have a "lifeboat" spaceship already in orbit around Mars to take you back to Earth? Maybe two of those? Because once you've got the development costs, actually building the spacecraft, building three instead of one, might not cost hugely more, and even launching them if we have a reasonably cost effective launch system.
Then - might that not be safer than the double fly by?
Just ideas.
But it depends on us developing methods of closed system habitats and reliable hardware that can last for 700 days without resupply from Earth. ISS is totally dependent on resupply every few months.
I think myself that until we have proved that a human occupied spacecraft can survive for a couple of years or more - say at the L2 position at far side of Moon without any resupply from the Earth - that we shouldn't consider interplanetary flights. Because, until then, the chance is surely very high indeed, surely, that the entire crew would die on the flight.
It's because you can get back from L2 in 2 days. And with hardly any fuel also - a simple lifeboat type method - always keep a crew vehicle attached to your space station - and you would also use it as a place you can retire to in emergency, with its own life support, and be back to Earth in a couple of days. It's a reasonably safe mission as space missions go.
While from Mars it can take over two years before you can get back.
For instance, if your oxygen regeneration or CO2 scrubbing fails, or your food supply is contaminated, or you get sick, then these are situations that would develop over days, plenty of time to get back from L2. For anything vital like that, no chance at all of getting back to Earth from Mars before the crew are either dead, or have resolved the issue by themselves.
Or if your crew get sick, as may happen in a long duration flight - that develops over months most likely. You would want to get back, perhaps in weeks or days, and can do that from L2. But the over two years return flight from Mars if it develops at an unfavourable time (e.g. close to start of mission) could easily be fatal in an illness easily treatable back on Earth.
You can also rush supplies from Earth to the Moon in an emergency. You can also communicate in close to real time with Earth - while at Mars then all your conversations have delays of up to 40 minutes between asking a question and getting a reply so the crew is essentially on their own for any emergency situation problem solving as it develops - emergency may well be over before they get a reply.
It's also arguably safer than a lunar surface mission at an early stage in our technology - when it is important to be able to return to Earth easily. This is a minor point but still, worth considering I think for the very first human missions "back to the Moon".
With a lunar surface mission, you have to launch from the surface of the Moon to get back to Earth, so what if your launcher to take you to orbit fails? With the L2, then you just have to separate, and use a gentle boost in zero g to go on a trajectory that takes you back to Earth - apart from the extra time involved to get to Earth, it is as easy as returning from the ISS.
Though Inspiration Mars shortens the total flight for Inspiration Mars to 500 days instead of 700, it does it by increasing the speed with which it hits the Earth system on the way back making it far harder to slow down when it gets back to Earth. That was one of the details that got turned up as his idea was discussed by experts after he announced it. And they also get such a short time at Mars.
I'm not sure they would bother to set it up with teleoperation capabilities for such a short visit to Mars, I mean even an hour or so would be worth doing, but - no mention of such things in the plan. Is just the aim to fire a human couple, confined in a tiny space together, physically, around Mars, I don't really get it as a concept. Sort of human cannonball - I got really interested when it was first announced but as the details became clearer I couldn't see the point.
If we are at a level of technology where we have to go for 500 days because the crew will die in a mission of 700 days, I think we are steering so close to the wind that we shouldn't attempt it at all.
And the Athena double fly by gives far more science return. And because it doesn't depend on a Venus flyby, you can do it every two years. And - don't see that it's going to be that significantly more expensive.
To review how it works - the first flyby puts the spacecraft into an orbit similar to that of Mars. Second flyby of Mars, half a Mars year later (one Earth year later) then puts it into a return trajectory to Earth.
And - after first flyby, because it goes into an orbit very similar to Mars - then the crew remain close to Mars for a long time, so you get a lot of time for fairly close teleoperation of vehicles on the surface.
So long as it is combined with spacecraft sent to the surface for the crew to operate -and surely other projects and countries would collaborate sending missions to he surface for them to control given the huge advantage of close up telepresence operation - then it would probably do as much in a few hours as other missions have done in years.
So - I vote for the double Athena flyby. Similar cost to the Inspiration Mars but better conceived.
Then after that I'd vote for the Herro plan which puts a human mission into a sun synchronous Molniya orbit around Mars - pretty much continuous tele-operation of rovers on the surface of Mars.
The advantage of the double Athena - like Inspiration Mars - is that it is a "free return" trajectory, only need fine adjustments through the entire program. So might be first.
But the HERRO - just takes you to a Mars capture orbit. And it does have some advantages for safety also. I wonder - what about sending a preliminary mission first to its intended orbit with fuel, food etc for the human crew? So before you set off, you know that you have a "lifeboat" spaceship already in orbit around Mars to take you back to Earth? Maybe two of those? Because once you've got the development costs, actually building the spacecraft, building three instead of one, might not cost hugely more, and even launching them if we have a reasonably cost effective launch system.
Then - might that not be safer than the double fly by?
Just ideas.
But it depends on us developing methods of closed system habitats and reliable hardware that can last for 700 days without resupply from Earth. ISS is totally dependent on resupply every few months.
I think myself that until we have proved that a human occupied spacecraft can survive for a couple of years or more - say at the L2 position at far side of Moon without any resupply from the Earth - that we shouldn't consider interplanetary flights. Because, until then, the chance is surely very high indeed, surely, that the entire crew would die on the flight.
MORE ON WHY THE L2 MISSION IS SO MUCH SAFER THAN A MISSION TO MARS ORBIT
It's because you can get back from L2 in 2 days. And with hardly any fuel also - a simple lifeboat type method - always keep a crew vehicle attached to your space station - and you would also use it as a place you can retire to in emergency, with its own life support, and be back to Earth in a couple of days. It's a reasonably safe mission as space missions go.
While from Mars it can take over two years before you can get back.
For instance, if your oxygen regeneration or CO2 scrubbing fails, or your food supply is contaminated, or you get sick, then these are situations that would develop over days, plenty of time to get back from L2. For anything vital like that, no chance at all of getting back to Earth from Mars before the crew are either dead, or have resolved the issue by themselves.
Or if your crew get sick, as may happen in a long duration flight - that develops over months most likely. You would want to get back, perhaps in weeks or days, and can do that from L2. But the over two years return flight from Mars if it develops at an unfavourable time (e.g. close to start of mission) could easily be fatal in an illness easily treatable back on Earth.
You can also rush supplies from Earth to the Moon in an emergency. You can also communicate in close to real time with Earth - while at Mars then all your conversations have delays of up to 40 minutes between asking a question and getting a reply so the crew is essentially on their own for any emergency situation problem solving as it develops - emergency may well be over before they get a reply.
It's also arguably safer than a lunar surface mission at an early stage in our technology - when it is important to be able to return to Earth easily. This is a minor point but still, worth considering I think for the very first human missions "back to the Moon".
With a lunar surface mission, you have to launch from the surface of the Moon to get back to Earth, so what if your launcher to take you to orbit fails? With the L2, then you just have to separate, and use a gentle boost in zero g to go on a trajectory that takes you back to Earth - apart from the extra time involved to get to Earth, it is as easy as returning from the ISS.
About the Author
Robert Walker
Writer of articles on Mars and Space issues - Software Developer of Tune Smithy, Bounce Metronome etc.Studied at Wolfson College, Oxford
Lives in Isle of Mull
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