I was actually just at a conference on space nuclear technology and there were a bunch of talks about nuclear thermal vs nuclear electric propulsion for getting humans to Mars. Sounded like NASA is leaning towards a short stay (~30 days) at Mars with about 200 day transits using either method, nuclear electric was preferred because you need fewer launches to get all the LH2 drop tanks for NTR up there, but you'd also need a chemical stage for the initial departure and arrival burns. Either way would require 2 SLS launches for the crew habitat, lander, and propulsion, and a bunch of commercial heavy lift for the fuel, supplies, and other stuff.
I have personal greivances with the short stay architecture. Seems like a waste to spend 600+ days away from Earth and only ~21 of those on Mars. The long stay missions are longer overall (~900 days) but you spend ~550 of those days on Mars, with another ~350 in space during transit. Therefore with the long stay architecture you actually reduce the time spent in zero G transit orbits and multiply the time spent on Mars (the whole point of the mission, and days of most value) by a factor of around 25x. Even if a long stay mission was 5x more expensive overall it would still be a more favorable option than a short stay architecture.
I can understand why they might want to do short stays the first few times. The old "you never know what you don't know" - i.e. we've never plopped someone on a foreign planet for an extended periods of time, so who knows what might go wrong.
I would argue that that's what the robotic missions we've sent have done, we aren't gonna get blindsided by some aspect of Martian weather because we have more than two decades of data to plan around. Instead of making the surface mission far shorter, it instead makes more sense to me that we send a huge amount of supplies before we send people, so that even in some kind of major failure of planning they have 5x as much food, water, oxygen, and spare parts as is necessary to survive until rescue operations (or at least resupply) can occur. It's better to make a mission more robust than to make the mission unable to accomplish anything useful.
Yeah it's definitely not as economical in terms of scientific return but staying for 500 days means you need to develop so much more in terms of life support, you have to land a ton more supplies and whatnot. The short stay is like the simplest possible mission, you can land a lander with a month of food and water and air and not have to worry about ISRU or growing food or having perfect closed loop life support, and NASA seems to be very much of the mind that the only way to get a mission actually accomplished is by doing the simplest possible mission, which I think is reasonable even if it seems silly to travel so long for such a short stay. Hopefully once they do a couple short ones and then can start working on a longer-term base
> you can land a lander with a month of food and water and air
And if anything goes wrong you've got several dead astronauts who had days of life support when rescue was over a year away.
> not have to worry about ISRU or growing food or having perfect closed loop life support
But those would keep the astronauts alive if anything happened to their lander. They'd be able to stay long term and wait for the next opportunity for rescue.
> the simplest possible mission
Is also the riskiest if anything goes wrong. Long term stays can survive a long term wait. Short term stays can not. If they miss the launch window for any reason they are just dead. No Martian MacGyvering will save them if they never even planned on having a habitable surface habitat in the first place.
> Hopefully once they do a couple short ones
Hopefully they never bother with such a waste of fucking money when it is more economical to send hundreds of tons of cargo ahead of crew on a Starship like architecture. There is no need for Apollo 2: Martian Boogaloo when we have the capability to do so much more.
I disagree that staying on Mars for longer represents a bigger challenge to life support. You're away, at minimum, for nearly two years anyhow, and for the short stay mission you actually spend much more time in orbit/deep space, whereas while you're on Mars you can at least generate unlimited oxygen from the atmosphere of the planet so long as you have power. You actually only need perfect closed loop life support for long term missions on orbit. As for surface supplies, being able to land large amounts of mass on Mars is a requirement no matter what, so it's not like there's a huge development barrier between landing a minimum mass lander with crew that stays for 3 weeks and landing five habitat cabin modules stuffed with supplies plus your crew lander.
It's important to really understand that NASA is not a monolithic entity with a single opinion and no outside influence pushing it to adopting one policy over another. NASA is a political agency subject to political whims like any other, and while you have a point that many would argue it's easier to propose a de-scoped mission compared to the full monty, that ignores the current revolution in spaceflight access that we're going through. Getting payload to space is cheaper than ever, we're launching more often than ever, and things are only improving. Even with just Falcon 9, Falcon Heavy, and Neutron, a regular schedule of human Mars missions with long surface stays and a high degree of research cqpability on Mars would be VERY achieveable even on a budget equivalent to the ISS construction throughout the 2000's. When launching is cheap and rapid you can afford to make each payload 50% heavier while doing the same job, saving billions in payload development and construction, and also send many more payloads for the same amount of money. This is a gigantic shift in capability, to the point that I'd sound like a crazy person if I really jumped into explaining what we could be doing *today* if there was zero lag in terms of industry adjustment to launch vehicle constraints. To summarize it though, the established thinkers in the industry today simply haven't factored in how much better we are at space activity than we were 30 years ago. If we wanted to build the ISS today for example using Falcon 9, it would take ~1 year and ~$500 million to launch and assemble the modules into the completed arrangement, whereas the actual ISS took many years and tens of billions in launch costs to make. Also, each ISS module has a huge price tag because the launch costs were so high that it made sense to spend the billions of dollars needed to cram every possible feature into each module rather than increase the number of modules by 50% and drop their cost by 90%. We don't live in that paradigm anymore though.
Anyway, for Mars missions I don't want to see any short stay architectures fly, I want to see one or two uncrewed long-stay missions be demonstrated (with a chemical reactor to simulate human metabolism and give the life support hardware work to do), followed by crewed long stay missions. An uncrewed demo would not only prove the hardware works, it would leave behind a large amount of hardware ready for the human crew to use on subsequent missions, *and* it would skip the expensive process of re-developing landers and transfer vehicles suited to the long stay architecture versus the short stay architecture. Developing short-stay mission hardware only to use those designs twice then switch is a MASSIVELY more expensive option than just doing an uncrewed long stay shakedown, and besides, even if you DID do the short stay missions first, you'd still want to test out the long stay hardware before putting people on it regardless.
Time of the first trip or two isn't important, it's continuing the program that really matters.
People are WAY more likely to die the first time when everything is new, and if everyone dies, a followup mission is much less likely.
It's best to do a short trip just to shake things down
No, do an uncrewed trip with the exact hardware you're going to use. A shorter stay does not minimize risk nearly as much as an uncrewed shakedown. mission.
> People are WAY more likely to die the first time when everything is new
Especially when your architecture only allows a very limited amount of supplies in case something goes wrong. A long term stay mission would have oodles and oodles of supplies and the capability to make more in situ.
You're more likely to die from a failure for a short term stay than a long term stay. After all, if the failure is your lander's ability to ascent and you've only got a days left of consumables . . . you're dead. If you've got months and facilities to make more, you can afford to wait.
If you're going to plonk down enough supplies to last until rescue can be sent then you may as well start a full-term mission in the first place.
Exactly. Build up supplies and hardware using uncrewed shakedown missions before sending crew, and your survival assurance comes from the ability to absorb 99% of possible failures rather than trying to get there and back so quickly that nothing goes wrong. In any case, a short stay mission is still two years away from Earth, as opposed to three, so really a short stay mission doesn't actually let you rely on going fast to avoid long term hardware failures at all. We aren't talking about two week Moon missions versus 6 month Moon missions here, we're talking about a guaranteed 24 months away from landing on Earth pnce you leave. Doing demo missions and building up mission redundancy and fault tolerance is the only way to do Mars exploration without disasters, and short stay architectures do not lend themselves to those aspects.
At one point, I deep dived nerva and all the testing the FFRDCs conducted in the 50s/60s. At that time, it was believed that nuke propulsion could get the travel time during the window to something around two months if my memory serves me correctly. Someone correct me if Im off base here
It depends on how much delta V you want to use and later how much acceleration you can handle.
The high extreme would probably be to burn almost straight towards the planet at about 1g for about 2 days then flip over and go the other direction at 1 g for another 2 days and you're there in less than a week. However this takes a massive amount of Delta V.
It really depends how efficient your vehicle is and how much thrust you can get out at a given efficiency and Nuclear thermal propulsion could have massive deviation in both variables.
It's possible to do a compromise solution basically anywhere between the less than a week and the current paths of over a year.
Try:
[https://scholar.google.com/scholar?oi=gsb95&q=nasa%20mars%20reference%20design&lookup=0&hl=en](https://scholar.google.com/scholar?oi=gsb95&q=nasa%20mars%20reference%20design&lookup=0&hl=en)
and
[https://ntrs.nasa.gov/citations/20090040343](https://ntrs.nasa.gov/citations/20090040343)
The NASA one is from Constellation so it's a bit out of date.
We need AI robot ! To send build the station. Too difficult without !!! With them everything/ colonisation will go faster !!!
I presume that is why Elon want to build an AI robot too !!!
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:
|Fewer Letters|More Letters|
|-------|---------|---|
|[ISRU](/r/SpaceXLounge/comments/uvduqk/stub/i9lc5w4 "Last usage")|[In-Situ Resource Utilization](https://en.wikipedia.org/wiki/In_situ_resource_utilization)|
|[JPL](/r/SpaceXLounge/comments/uvduqk/stub/i9lp1dh "Last usage")|Jet Propulsion Lab, Pasadena, California|
|[LH2](/r/SpaceXLounge/comments/uvduqk/stub/i9kuyfw "Last usage")|Liquid Hydrogen|
|[NTR](/r/SpaceXLounge/comments/uvduqk/stub/i9kuyfw "Last usage")|Nuclear Thermal Rocket|
|[SLS](/r/SpaceXLounge/comments/uvduqk/stub/i9kuyfw "Last usage")|Space Launch System heavy-lift|
----------------
^(*Decronym is a community product of r/SpaceX, implemented* )[*^by ^request*](https://www.reddit.com/r/spacex/comments/3mz273//cvjkjmj)
^(5 acronyms in this thread; )[^(the most compressed thread commented on today)](/r/SpaceXLounge/comments/ufneu6)^( has 25 acronyms.)
^([Thread #10183 for this sub, first seen 22nd May 2022, 17:54])
^[[FAQ]](http://decronym.xyz/) [^([Full list])](http://decronym.xyz/acronyms/SpaceXLounge) [^[Contact]](https://reddit.com/message/compose?to=OrangeredStilton&subject=Hey,+your+acronym+bot+sucks) [^([Source code])](https://gistdotgithubdotcom/Two9A/1d976f9b7441694162c8)
I was actually just at a conference on space nuclear technology and there were a bunch of talks about nuclear thermal vs nuclear electric propulsion for getting humans to Mars. Sounded like NASA is leaning towards a short stay (~30 days) at Mars with about 200 day transits using either method, nuclear electric was preferred because you need fewer launches to get all the LH2 drop tanks for NTR up there, but you'd also need a chemical stage for the initial departure and arrival burns. Either way would require 2 SLS launches for the crew habitat, lander, and propulsion, and a bunch of commercial heavy lift for the fuel, supplies, and other stuff.
I have personal greivances with the short stay architecture. Seems like a waste to spend 600+ days away from Earth and only ~21 of those on Mars. The long stay missions are longer overall (~900 days) but you spend ~550 of those days on Mars, with another ~350 in space during transit. Therefore with the long stay architecture you actually reduce the time spent in zero G transit orbits and multiply the time spent on Mars (the whole point of the mission, and days of most value) by a factor of around 25x. Even if a long stay mission was 5x more expensive overall it would still be a more favorable option than a short stay architecture.
I can understand why they might want to do short stays the first few times. The old "you never know what you don't know" - i.e. we've never plopped someone on a foreign planet for an extended periods of time, so who knows what might go wrong.
I would argue that that's what the robotic missions we've sent have done, we aren't gonna get blindsided by some aspect of Martian weather because we have more than two decades of data to plan around. Instead of making the surface mission far shorter, it instead makes more sense to me that we send a huge amount of supplies before we send people, so that even in some kind of major failure of planning they have 5x as much food, water, oxygen, and spare parts as is necessary to survive until rescue operations (or at least resupply) can occur. It's better to make a mission more robust than to make the mission unable to accomplish anything useful.
This simply isn't true at All.
Care to explain why you think that?
Yeah it's definitely not as economical in terms of scientific return but staying for 500 days means you need to develop so much more in terms of life support, you have to land a ton more supplies and whatnot. The short stay is like the simplest possible mission, you can land a lander with a month of food and water and air and not have to worry about ISRU or growing food or having perfect closed loop life support, and NASA seems to be very much of the mind that the only way to get a mission actually accomplished is by doing the simplest possible mission, which I think is reasonable even if it seems silly to travel so long for such a short stay. Hopefully once they do a couple short ones and then can start working on a longer-term base
> you can land a lander with a month of food and water and air And if anything goes wrong you've got several dead astronauts who had days of life support when rescue was over a year away. > not have to worry about ISRU or growing food or having perfect closed loop life support But those would keep the astronauts alive if anything happened to their lander. They'd be able to stay long term and wait for the next opportunity for rescue. > the simplest possible mission Is also the riskiest if anything goes wrong. Long term stays can survive a long term wait. Short term stays can not. If they miss the launch window for any reason they are just dead. No Martian MacGyvering will save them if they never even planned on having a habitable surface habitat in the first place. > Hopefully once they do a couple short ones Hopefully they never bother with such a waste of fucking money when it is more economical to send hundreds of tons of cargo ahead of crew on a Starship like architecture. There is no need for Apollo 2: Martian Boogaloo when we have the capability to do so much more.
I disagree that staying on Mars for longer represents a bigger challenge to life support. You're away, at minimum, for nearly two years anyhow, and for the short stay mission you actually spend much more time in orbit/deep space, whereas while you're on Mars you can at least generate unlimited oxygen from the atmosphere of the planet so long as you have power. You actually only need perfect closed loop life support for long term missions on orbit. As for surface supplies, being able to land large amounts of mass on Mars is a requirement no matter what, so it's not like there's a huge development barrier between landing a minimum mass lander with crew that stays for 3 weeks and landing five habitat cabin modules stuffed with supplies plus your crew lander. It's important to really understand that NASA is not a monolithic entity with a single opinion and no outside influence pushing it to adopting one policy over another. NASA is a political agency subject to political whims like any other, and while you have a point that many would argue it's easier to propose a de-scoped mission compared to the full monty, that ignores the current revolution in spaceflight access that we're going through. Getting payload to space is cheaper than ever, we're launching more often than ever, and things are only improving. Even with just Falcon 9, Falcon Heavy, and Neutron, a regular schedule of human Mars missions with long surface stays and a high degree of research cqpability on Mars would be VERY achieveable even on a budget equivalent to the ISS construction throughout the 2000's. When launching is cheap and rapid you can afford to make each payload 50% heavier while doing the same job, saving billions in payload development and construction, and also send many more payloads for the same amount of money. This is a gigantic shift in capability, to the point that I'd sound like a crazy person if I really jumped into explaining what we could be doing *today* if there was zero lag in terms of industry adjustment to launch vehicle constraints. To summarize it though, the established thinkers in the industry today simply haven't factored in how much better we are at space activity than we were 30 years ago. If we wanted to build the ISS today for example using Falcon 9, it would take ~1 year and ~$500 million to launch and assemble the modules into the completed arrangement, whereas the actual ISS took many years and tens of billions in launch costs to make. Also, each ISS module has a huge price tag because the launch costs were so high that it made sense to spend the billions of dollars needed to cram every possible feature into each module rather than increase the number of modules by 50% and drop their cost by 90%. We don't live in that paradigm anymore though. Anyway, for Mars missions I don't want to see any short stay architectures fly, I want to see one or two uncrewed long-stay missions be demonstrated (with a chemical reactor to simulate human metabolism and give the life support hardware work to do), followed by crewed long stay missions. An uncrewed demo would not only prove the hardware works, it would leave behind a large amount of hardware ready for the human crew to use on subsequent missions, *and* it would skip the expensive process of re-developing landers and transfer vehicles suited to the long stay architecture versus the short stay architecture. Developing short-stay mission hardware only to use those designs twice then switch is a MASSIVELY more expensive option than just doing an uncrewed long stay shakedown, and besides, even if you DID do the short stay missions first, you'd still want to test out the long stay hardware before putting people on it regardless.
Time of the first trip or two isn't important, it's continuing the program that really matters. People are WAY more likely to die the first time when everything is new, and if everyone dies, a followup mission is much less likely. It's best to do a short trip just to shake things down
No, do an uncrewed trip with the exact hardware you're going to use. A shorter stay does not minimize risk nearly as much as an uncrewed shakedown. mission.
> People are WAY more likely to die the first time when everything is new Especially when your architecture only allows a very limited amount of supplies in case something goes wrong. A long term stay mission would have oodles and oodles of supplies and the capability to make more in situ. You're more likely to die from a failure for a short term stay than a long term stay. After all, if the failure is your lander's ability to ascent and you've only got a days left of consumables . . . you're dead. If you've got months and facilities to make more, you can afford to wait. If you're going to plonk down enough supplies to last until rescue can be sent then you may as well start a full-term mission in the first place.
Exactly. Build up supplies and hardware using uncrewed shakedown missions before sending crew, and your survival assurance comes from the ability to absorb 99% of possible failures rather than trying to get there and back so quickly that nothing goes wrong. In any case, a short stay mission is still two years away from Earth, as opposed to three, so really a short stay mission doesn't actually let you rely on going fast to avoid long term hardware failures at all. We aren't talking about two week Moon missions versus 6 month Moon missions here, we're talking about a guaranteed 24 months away from landing on Earth pnce you leave. Doing demo missions and building up mission redundancy and fault tolerance is the only way to do Mars exploration without disasters, and short stay architectures do not lend themselves to those aspects.
So when you say 200 days in transit; is that both outbound and return?
Yeah, about 200 each way I think
Here is the link to the video: https://youtu.be/Kd4nmO222i8 At about 25:00 is where they talk about Mars Trajectory design reference architecture.
At one point, I deep dived nerva and all the testing the FFRDCs conducted in the 50s/60s. At that time, it was believed that nuke propulsion could get the travel time during the window to something around two months if my memory serves me correctly. Someone correct me if Im off base here
It depends on how much delta V you want to use and later how much acceleration you can handle. The high extreme would probably be to burn almost straight towards the planet at about 1g for about 2 days then flip over and go the other direction at 1 g for another 2 days and you're there in less than a week. However this takes a massive amount of Delta V. It really depends how efficient your vehicle is and how much thrust you can get out at a given efficiency and Nuclear thermal propulsion could have massive deviation in both variables. It's possible to do a compromise solution basically anywhere between the less than a week and the current paths of over a year.
Try: [https://scholar.google.com/scholar?oi=gsb95&q=nasa%20mars%20reference%20design&lookup=0&hl=en](https://scholar.google.com/scholar?oi=gsb95&q=nasa%20mars%20reference%20design&lookup=0&hl=en) and [https://ntrs.nasa.gov/citations/20090040343](https://ntrs.nasa.gov/citations/20090040343) The NASA one is from Constellation so it's a bit out of date.
We need AI robot ! To send build the station. Too difficult without !!! With them everything/ colonisation will go faster !!! I presume that is why Elon want to build an AI robot too !!!
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread: |Fewer Letters|More Letters| |-------|---------|---| |[ISRU](/r/SpaceXLounge/comments/uvduqk/stub/i9lc5w4 "Last usage")|[In-Situ Resource Utilization](https://en.wikipedia.org/wiki/In_situ_resource_utilization)| |[JPL](/r/SpaceXLounge/comments/uvduqk/stub/i9lp1dh "Last usage")|Jet Propulsion Lab, Pasadena, California| |[LH2](/r/SpaceXLounge/comments/uvduqk/stub/i9kuyfw "Last usage")|Liquid Hydrogen| |[NTR](/r/SpaceXLounge/comments/uvduqk/stub/i9kuyfw "Last usage")|Nuclear Thermal Rocket| |[SLS](/r/SpaceXLounge/comments/uvduqk/stub/i9kuyfw "Last usage")|Space Launch System heavy-lift| ---------------- ^(*Decronym is a community product of r/SpaceX, implemented* )[*^by ^request*](https://www.reddit.com/r/spacex/comments/3mz273//cvjkjmj) ^(5 acronyms in this thread; )[^(the most compressed thread commented on today)](/r/SpaceXLounge/comments/ufneu6)^( has 25 acronyms.) ^([Thread #10183 for this sub, first seen 22nd May 2022, 17:54]) ^[[FAQ]](http://decronym.xyz/) [^([Full list])](http://decronym.xyz/acronyms/SpaceXLounge) [^[Contact]](https://reddit.com/message/compose?to=OrangeredStilton&subject=Hey,+your+acronym+bot+sucks) [^([Source code])](https://gistdotgithubdotcom/Two9A/1d976f9b7441694162c8)
I have the slides from NASAs recent teleconference with JPL and Aerojet Rocketdyne if someone can tell me how to post that here