One of the fastest ways to the Moon (not counting using foreign hardware) is probably this approach, here:http://www.nasa.gov/pdf/65851main_spacehab.pdfFastest way to Mars may be a similar approach.
Quote from: Robotbeat on 09/19/2011 08:47 pmOne of the fastest ways to the Moon (not counting using foreign hardware) is probably this approach, here:http://www.nasa.gov/pdf/65851main_spacehab.pdfFastest way to Mars may be a similar approach.Probably not, because it also tries to bring people back. Its logically quite a bit cheaper to send people one-way.This is just to demonstrate again, if you don't specify the reasons for going, its impossible to work out the optimum solutions.
What is the cheapest and fastest way to send people to the moon or mars . Is that using Falcon ,SLS or going back to the constellation project that Bush wanted !! I keep reading these anti-SLS or anti-Falcon threads but no clear posts in any of these threads want is the cheapest and fastest way to go to the moon or mars.
Can we go to the moon, yes, but not simply nor cheaply. Falcon is ill suited, due to the lack of both a high energy orbital stage as well as long duration capability.
Atlas and Delta are your best bets there, but you are talking a three or four launch architecture, which would take a month of preparation before your moon mission due in part to the results of the Griffin era Constellation changes.
Before Griffin, the CEV was nothing but a way to and from orbit, with on-orbit systems for going BEO. As a result, the CEV was lightweight and minimalist.
Using the Shuttle as a baseline, for 2 missions per year, with the Shuttle it costs $3.2 billion, for 5 it cost $3.6 billion.
QuoteCan we go to the moon, yes, but not simply nor cheaply. Falcon is ill suited, due to the lack of both a high energy orbital stage as well as long duration capability. What do you mean here.
QuoteAtlas and Delta are your best bets there, but you are talking a three or four launch architecture, which would take a month of preparation before your moon mission due in part to the results of the Griffin era Constellation changes. But would it be cheaper and could you go to the moon before SLS is built that say go to the moon by 2016?
Quote Before Griffin, the CEV was nothing but a way to and from orbit, with on-orbit systems for going BEO. As a result, the CEV was lightweight and minimalist. So you are saying CEV is way too small.They need some thing bigger?
Quote Using the Shuttle as a baseline, for 2 missions per year, with the Shuttle it costs $3.2 billion, for 5 it cost $3.6 billion.What $3.6 billion for 5 shuttle launch that you can do with 1 SLS launch?Well SLS or saturn-v is what you will need if you want to go to Mars has Falcon or constellation project I do not think it will get you there.The Falcon or constellation project is not built for that .
Quote from: nec207 on 09/19/2011 09:32 pmQuoteCan we go to the moon, yes, but not simply nor cheaply. Falcon is ill suited, due to the lack of both a high energy orbital stage as well as long duration capability. What do you mean here.Just that. SpaceX is LEO-centric, anything further out their performance drops significantly. That is why the Falcon 9 may deliver ~10 metric tons to LEO, but less than 2 to geo-stationary orbits, while the Atlas V 401 delivers the same ~10 metric tons to LEO, but over twice as much to geo-stationary, it uses a high-energy upper stage, the Centaur. The Proton, using Blok-DM and Briz-M, uses long-duration capability to similarly deliver a higher payload percentage....
Quote from: Downix on 09/19/2011 09:48 pmQuote from: nec207 on 09/19/2011 09:32 pmQuoteCan we go to the moon, yes, but not simply nor cheaply. Falcon is ill suited, due to the lack of both a high energy orbital stage as well as long duration capability. What do you mean here.Just that. SpaceX is LEO-centric, anything further out their performance drops significantly. That is why the Falcon 9 may deliver ~10 metric tons to LEO, but less than 2 to geo-stationary orbits, while the Atlas V 401 delivers the same ~10 metric tons to LEO, but over twice as much to geo-stationary, it uses a high-energy upper stage, the Centaur. The Proton, using Blok-DM and Briz-M, uses long-duration capability to similarly deliver a higher payload percentage....More importantly, Proton has lots of stages. Falcon Heavy also is essentially a three-stage vehicle, so would get decent performance to high energy orbits (well, better performance to GTO than anything available today, by far).
No, I'm saying that the 2005 CEV was a lighter weight craft than Orion is today, with more mission profile options. Orion is heavy, but for it's planned mission is incredibly well designed, to the point nothing else can touch it. If you step out of that mission, it's over-built.
Orion is significantly larger than Apollo. And, just like Apollo, it was designed to be paired with a lander.If you had the option of riding Warpstar-1, you might not want to go to the moon in Orion. As it is, I think you're being a bit picky...It is, of course, much too small for Mars, which is why it's never seriously proposed as a habitat for a Mars transit. It's only used to get the crew to the spacecraft before it leaves and to return them to Earth after it comes back.
Quote from: Robotbeat on 09/19/2011 09:53 pmQuote from: Downix on 09/19/2011 09:48 pmQuote from: nec207 on 09/19/2011 09:32 pmQuoteCan we go to the moon, yes, but not simply nor cheaply. Falcon is ill suited, due to the lack of both a high energy orbital stage as well as long duration capability. What do you mean here.Just that. SpaceX is LEO-centric, anything further out their performance drops significantly. That is why the Falcon 9 may deliver ~10 metric tons to LEO, but less than 2 to geo-stationary orbits, while the Atlas V 401 delivers the same ~10 metric tons to LEO, but over twice as much to geo-stationary, it uses a high-energy upper stage, the Centaur. The Proton, using Blok-DM and Briz-M, uses long-duration capability to similarly deliver a higher payload percentage....More importantly, Proton has lots of stages. Falcon Heavy also is essentially a three-stage vehicle, so would get decent performance to high energy orbits (well, better performance to GTO than anything available today, by far).When is Falcon Heavy going to be going in service and could they use that to go to the moon ?Yes but the Atlas and Delta rockets is going be able to go in service alot faster than SLS?
Right, but Orion does offer the ability to be an emergency vehicle should all hell break loose, with enough delta-v to offer a return to earth on its own from LLO.
Quote from: savuporo on 09/19/2011 08:56 pmQuote from: Robotbeat on 09/19/2011 08:47 pmOne of the fastest ways to the Moon (not counting using foreign hardware) is probably this approach, here:http://www.nasa.gov/pdf/65851main_spacehab.pdfFastest way to Mars may be a similar approach.Probably not, because it also tries to bring people back. Its logically quite a bit cheaper to send people one-way.This is just to demonstrate again, if you don't specify the reasons for going, its impossible to work out the optimum solutions.Did you actually look at all of what is in that pdf? There is one-way payload capabilities shown on page 8 (before the two-way manned capabilities shown on page 9).
Quote from: Robotbeat on 09/19/2011 09:05 pmQuote from: savuporo on 09/19/2011 08:56 pmQuote from: Robotbeat on 09/19/2011 08:47 pmOne of the fastest ways to the Moon (not counting using foreign hardware) is probably this approach, here:http://www.nasa.gov/pdf/65851main_spacehab.pdfFastest way to Mars may be a similar approach.Probably not, because it also tries to bring people back. Its logically quite a bit cheaper to send people one-way.This is just to demonstrate again, if you don't specify the reasons for going, its impossible to work out the optimum solutions.Did you actually look at all of what is in that pdf? There is one-way payload capabilities shown on page 8 (before the two-way manned capabilities shown on page 9).Yes i did, but you did not read my reply. I said, sending people (not cargo) one way, especially sending a single person one way can be obviously done cheaper and sooner.Once again, without specifying the goal of going, its impossible to perform any useful analysis on the optimum solutions. I am wearing that drum out, just about now ..
The cargo module is pressurized in the example I linked to ( http://is.gd/WDtF2q ); you could use it to send people one-way. I know you had a larger point to prove, but some architectures are more flexible and better at being optimal given almost any sort of goals than other architectures.
well still no one answered if Falcon Heavy could they use that to go to the moon , or if Atlas and Delta rockets is going be able to go in service alot faster than SLS?
Quote from: nec207 on 09/19/2011 11:12 pmwell still no one answered if Falcon Heavy could they use that to go to the moon , or if Atlas and Delta rockets is going be able to go in service alot faster than SLS? Yes and yes.http://www.nasa.gov/pdf/65851main_spacehab.pdfFalcon 9 or Falcon Heavy could be used in place of Atlas V and Delta IV... I believe in this particular (LEO assembly) architecture, it could be done with only Falcon 9 or only Atlas V or only Delta IV... The important parts are the spacecraft, not the launch vehicles (which already exist).
So you think Atlas V and Delta IV could go in service alot faster than SLS?
Yes the spacecraft is important but so is the launch vehicles . We have Orion but we do not have a launch vehicles .
If Atlas V or only Delta IV can go in service by 2016 than we could go to the moon before SLS goes in service.
What is the cheapest and fastest way to send people to the moon or mars .
Quote from: nec207 on 09/19/2011 06:23 pmWhat is the cheapest and fastest way to send people to the moon or mars .An ordinary coffin on top of a Falcon 9 should work nicely for about $60 million.
Quote from: nec207 on 09/19/2011 11:36 pmSo you think Atlas V and Delta IV could go in service alot faster than SLS?QuoteYes the spacecraft is important but so is the launch vehicles . We have Orion but we do not have a launch vehicles .We have already launch vehicles, but no spacecraft (no capsule, no lander).
Quote from: nec207 on 09/19/2011 11:36 pmIf Atlas V or only Delta IV can go in service by 2016 than we could go to the moon before SLS goes in service.This is an incredibly surreal discussion. The EELVs you mention have been in service for years.
We have Orion .
Than why is NASA not doing any thing for the next 10 years than ?
Quote from: nec207 on 09/20/2011 12:04 amWe have Orion .Not yet. And you cannot land on the moon without a lander. A lander and a service module are the crucial missing pieces. We already have adequate launch vehicles, with another one on the way, and Dragon could be modified for beyond LEO.
So if we have launch vehicles why is NASA not using them .
Why is NASA not working on lander or service module.
Quote from: nec207 on 09/20/2011 12:06 amThan why is NASA not doing any thing for the next 10 years than ?Because they want to develop SLS + MPCV.
Quote from: nec207 on 09/20/2011 12:10 amSo if we have launch vehicles why is NASA not using them .Because they want to develop their own.QuoteWhy is NASA not working on lander or service module.They are working on the service module. It could even have commonality with the lander, as was the plan with Altair. But they have no money to do a lander, especially if they're also working on a crew module and SLS.
Quote from: mmeijeri on 09/20/2011 12:08 amQuote from: nec207 on 09/20/2011 12:04 amWe have Orion .Not yet. And you cannot land on the moon without a lander. A lander and a service module are the crucial missing pieces. We already have adequate launch vehicles, with another one on the way, and Dragon could be modified for beyond LEO.So if we have launch vehicles why is NASA not using them .Why is NASA not working on lander or service module.
Quote from: nec207 on 09/20/2011 12:10 amSo if we have launch vehicles why is NASA not using them .Because of politics. Read some other threads here.
I still do not know if SLS is going to be cheaper than any of the other launch vehicles .
Quote from: nec207 on 09/20/2011 12:14 amI still do not know if SLS is going to be cheaper than any of the other launch vehicles .It is certain to be more expensive if you count development costs, as you should. In fact that is precisely why certain influential politicians want it.
It may be more expensive to built it but it may be cheaper to put payload in space
and the other launch vehicles may be no good to go to mars.
Quote from: savuporo on 09/20/2011 12:15 amQuote from: nec207 on 09/20/2011 12:10 amSo if we have launch vehicles why is NASA not using them .Because of politics. Read some other threads here.With out politics getting in way of these threads than may be the people here at this web site and other web sites should sign a petition that 10 years is unacceptable.
The commercial competition are not planning to go to mars any time soon.
That me say this again if the SLS is the same or more costly than the apollo program ,space shuttle and project constellation proposed by president Bush that all got slash to to cost. Than it is a know fact that SLS is going to get scrapped before the first flight or after 2 or 3 launches.
Only if this brings space cost down or much cheaper of putting payload intospace.It would have to be cheaper than the apollo program ,shuttle program and project constellation if NOT it will be doomed like those programs too.
It really won't matter too much whether explorers get themselves and their equipment to the base camps on a large launcher like SLS, or medium launchers like the EELVs, Ariane, Proton, and HLV.
One of SLS's advantages, especially for Mars, is that it can launch very large pieces (both mass-wise and size-wise) in one shot, which helps with architecture design.
The answers to the questions of "which launcher is cheaper/faster/better for lunar/Mars missions" depend on assumptions about architecture and mission rate.
Quote from: 93143 on 09/20/2011 01:38 amOne of SLS's advantages, especially for Mars, is that it can launch very large pieces (both mass-wise and size-wise) in one shot, which helps with architecture design.No, it doesn't, not if you allow for propellant transfer, as you should.
As for crowds of anti-SLS posters: this whole site is pro-SLS by 2:1...
The objective is not a flags-and-footprints mission; we want to get serious infrastructure out there. (Or not, but IMO the answer to the thread's question does depend on this.)
That seems likely. And from the perspective of someone who passionately wants to see commercial development of space, it is the least bad thing we can hope for. Because after that, maybe we could give competitive procurement another try. Depressing, isn't it?
Quote from: mmeijeri on 09/20/2011 12:26 amQuote from: nec207 on 09/20/2011 12:14 amI still do not know if SLS is going to be cheaper than any of the other launch vehicles .It is certain to be more expensive if you count development costs, as you should. In fact that is precisely why certain influential politicians want it.It may be more expensive to built it but it may be cheaper to put payload in space and the other launch vehicles may be no good to go to mars.
Quote from: 93143 on 09/20/2011 01:38 amOne of SLS's advantages, especially for Mars, is that it can launch very large pieces (both mass-wise and size-wise) in one shot, which helps with architecture design.No, it doesn't, not if you allow for propellant transfer, as you should. As for crowds of anti-SLS posters: this whole site is pro-SLS by 2:1...
SLS is expensive if you don't use it much, but as you ramp up it gets cheaper faster than the smaller rockets do.
When Constellation fans said "go back to the moon", they didn't mean "fire someone's ashes into a crater with a Pegasus". They meant a permanently-manned base, operating in parallel with sortie missions using large pressurized rovers all over the lunar surface. ..
Quote from: 93143 on 09/20/2011 02:18 amThe objective is not a flags-and-footprints mission; we want to get serious infrastructure out there. (Or not, but IMO the answer to the thread's question does depend on this.)See right there, perfect example of assumptions that people enter the discussions with and fail to check at the door. See, the thread topic is "how to get human(s) to the moon OR mars in the fastest and cheapest way possible" and you start speaking about serious infrastructure.Yours is a valid and fine goal, i'd be fully behind that, but its got nothing to do with the optimum solution for the question at hand.I keep ranting about this, as i feel if people would start more seriously articulating the end goals the discussions would be far more fruitful.
I say again if it is the same or more than the apollo program ,shuttle program or project constellation if is doomed like the apollo program ,shuttle program or project constellation.
SLS isn't going to be used enough to justify the costs of it.
Positive, as will many of the negative votes when they see the improved schedule and flight rate.
Quote from: 93143 on 09/20/2011 02:58 amWhen Constellation fans said "go back to the moon", they didn't mean "fire someone's ashes into a crater with a Pegasus". They meant a permanently-manned base, operating in parallel with sortie missions using large pressurized rovers all over the lunar surface. ..... while completely failing to articulate any end goals for such antics. You see, because if all you want is to have a few government employees sitting in a lunar base with no particular purpose and "flying sorties", your optimal mission architectures will still be very significantly different from other types of lunar bases, where you might want to focus on things like industrializing moon, developing key technologies for eventual settlement, or just building a huge theme park for hundreds of wealthy tourist to visit.The "why" and goals discussion goes a little deeper than how many NASA astronauts and how often. This seems to bother a lot of people ..
You're missing my point. All I meant was that "go to the moon or mars" can carry the sort of unstated assumptions you're complaining about, and thus it is unjustified to assume it means a minimalistic stunt mission. Especially when the question seems to have been about launch vehicles specifically.
For the past 50 years progress is staggering do to cost , programs get cut or do not run for long.Ask most people in the 60`s thay would say by 2015 we would have been to every place in the solar system and have moon base and mars base. And by 2050 or less people living on mars and the moon.
Shuttle wasn't cancelled due to costs. It lasted 30 years, and would have kept right on going if it weren't for the Columbia accident.SLS looks like it will cost significantly less per year to keep going than the Shuttle did.
That depends on what he means by "go to the moon or mars" (I did acknowledge this).When Constellation fans said "go back to the moon", they didn't mean "fire someone's ashes into a crater with a Pegasus". They meant a permanently-manned base, operating in parallel with sortie missions using large pressurized rovers all over the lunar surface....
Quote from: mmeijeri on 09/20/2011 01:50 amQuote from: 93143 on 09/20/2011 01:38 amOne of SLS's advantages, especially for Mars, is that it can launch very large pieces (both mass-wise and size-wise) in one shot, which helps with architecture design.No, it doesn't, not if you allow for propellant transfer, as you should. As for crowds of anti-SLS posters: this whole site is pro-SLS by 2:1...Propellant transfer doesn't solve the problem of Mars EDL. To land humans on the surface of mars the lander needs an entry mass of 100-150mt....
I do fear SLS may not be the fastest way to get to the moon or mars
Its especially unjustified to try and shoehorn in a particular end goal specifically tailored to meet a particular yet-to-be-built launch vehicle constraints.
Quote from: 93143 on 09/20/2011 02:58 amThat depends on what he means by "go to the moon or mars" (I did acknowledge this).When Constellation fans said "go back to the moon", they didn't mean "fire someone's ashes into a crater with a Pegasus". They meant a permanently-manned base, operating in parallel with sortie missions using large pressurized rovers all over the lunar surface....None of those things require a larger launch vehicle than we have now, so why accuse those who (correctly) say that current launch vehicles are adequate of being "anti-" whatever?
Quote from: nec207 on 09/20/2011 03:56 amFor the past 50 years progress is staggering do to cost , programs get cut or do not run for long.Ask most people in the 60`s thay would say by 2015 we would have been to every place in the solar system and have moon base and mars base. And by 2050 or less people living on mars and the moon.If people "living on the mars and moon by 2050" is your end goal, then the launch vehicle choice to get there soon and fast is about the last thing you want to worry about.How about trying to figure out how could they actually live there, how would they sustain themselves and who would pay for it ? From there, you can start working backwards trying to identify which technologies and funding sources are we still lacking for this to happen, what are the realistic timescales do obtain these, and so on.
The claims around here are that under some circumstances, restrictions and conditions SLS and HLVs in general would start to make sense, but nobody has explained what these constraints would be. Presumably because these would be very contrived indeed.
Quote from: Robotbeat on 09/20/2011 04:18 amQuote from: 93143 on 09/20/2011 02:58 amThat depends on what he means by "go to the moon or mars" (I did acknowledge this).When Constellation fans said "go back to the moon", they didn't mean "fire someone's ashes into a crater with a Pegasus". They meant a permanently-manned base, operating in parallel with sortie missions using large pressurized rovers all over the lunar surface....None of those things require a larger launch vehicle than we have now, so why accuse those who (correctly) say that current launch vehicles are adequate of being "anti-" whatever?Plus, its not even the most cost-optimal or time-optimal way of doing any of these things, for whatever purpose.The claims around here are that under some circumstances, restrictions and conditions SLS and HLVs in general would start to make sense, but nobody has explained what these constraints would be. Presumably because these would be very contrived indeed.Launch a caterpillar D9 bulldozer to the moon in one piece ? Even that doesnt need an SLS, you know.
And with this last post, this thread has become officially too silly.It does not appear to be worth taking any further.
He is saying SLS or HLV`s are much cheaper at putting lots of tons into space.
And much faster than going up many times and than the construction of putting it all together .It is faster and cheaper to send SLS than having to go up 15 or 20 times.
To go to mars or space mining you need SLS from what people say may be not the moon but mars or space mining you need SLS.
You're stating it too simply. 15 or 20 EELV Heavy launches per year is close to the breakpoint where SLS is cheaper,
though Falcon should still beat it, at least to LEO. It's the spacecraft costs, complexity, and extra mass overhead that may (depending on exactly what it is you're doing) make SLS the best choice.
Space mining is not really near-term, even in the way Mars is. And the word "need" may be a bit strong. But it can help. Perhaps a lot, if the program is bold and robustly funded (always the catch).
QuoteYou're stating it too simply. 15 or 20 EELV Heavy launches per year is close to the breakpoint where SLS is cheaper, With out SLS or HLV you will have to go up many times 15 or 20 times to put all those little tons to make one big ton that is where it may be more costly and take longer to get to where you are going.
Quotethough Falcon should still beat it, at least to LEO. It's the spacecraft costs, complexity, and extra mass overhead that may (depending on exactly what it is you're doing) make SLS the best choice.SLS can put 130 tons in space in one shot I do not think Falcon can come any where close.
What does spacecraft costs, complexity, and extra mass overhead have to do with Launch vehicle.
QuoteSpace mining is not really near-term, even in the way Mars is. And the word "need" may be a bit strong. But it can help. Perhaps a lot, if the program is bold and robustly funded (always the catch). Well Obama proposed going to mars and doing space mining some where around 2025 or 2030.
Quote from: notsorandom on 09/20/2011 03:19 amQuote from: mmeijeri on 09/20/2011 01:50 amQuote from: 93143 on 09/20/2011 01:38 amOne of SLS's advantages, especially for Mars, is that it can launch very large pieces (both mass-wise and size-wise) in one shot, which helps with architecture design.No, it doesn't, not if you allow for propellant transfer, as you should. As for crowds of anti-SLS posters: this whole site is pro-SLS by 2:1...Propellant transfer doesn't solve the problem of Mars EDL. To land humans on the surface of mars the lander needs an entry mass of 100-150mt....That's just plain false.If you land an empty ascent vehicle beforehand that becomes filled with ISRU-derived propellants, nothing even near 100mT is needed as an entry mass (probably could make do with just 10mT or less landed dry mass at a time...). And besides, 100mT entry mass still requires ballutes or other more difficult EDL technology.Heck, the Apollo lunar module, which could probably fit 3 in a pinch (after all, Apollo 17 had over 100kg of samples, plus the two astronauts), and had enough delta-v for a Mars ascent vehicle (if not thrust) weighed only about 4 or 5 tons dry and could have considerable weight shaved off if it used modern electronics and batteries and aluminum-lithium alloysIt also depends if you want a crew of 8 (like some of the Mars architectures had) or a smaller crew of 6, 4, or even 2 (say, for the short-stay missions... some crew could stay on orbit, ala Apollo).
Quote from: mmeijeri on 09/20/2011 01:50 amQuote from: 93143 on 09/20/2011 01:38 amOne of SLS's advantages, especially for Mars, is that it can launch very large pieces (both mass-wise and size-wise) in one shot, which helps with architecture design.No, it doesn't, not if you allow for propellant transfer, as you should. As for crowds of anti-SLS posters: this whole site is pro-SLS by 2:1...Propellant transfer doesn't solve the problem of Mars EDL. To land humans on the surface of mars the lander needs an entry mass of 100-150mt. The percentage of a Mars lander that is fuel is not above 50 percent meaning that a Falcon Heavy could not lift one dry. In other words the unfueled mass of the lander is still too much for LVs smaller then SLS to launch into LEO. That does not mean that we need the whole 130mt of SLS with propellant transfer, the version without the upper stage may be enough. Another issue current launcher will have with getting a Mars lander into LEO will be the diameter of the heat shield. The extra fairing diameter of up to 10 or 12 meters will really simplify things compared with the 5m of currently available launchers. Mars EDL is a huge challenge. With our current technology most of Mars' surface is inaccessible and we can not put more then 1mt on the ground. I'm attaching a presentation on crewed Mars EDL if people are interested.
Quote from: notsorandom on 09/20/2011 03:19 amQuote from: mmeijeri on 09/20/2011 01:50 amQuote from: 93143 on 09/20/2011 01:38 amOne of SLS's advantages, especially for Mars, is that it can launch very large pieces (both mass-wise and size-wise) in one shot, which helps with architecture design.No, it doesn't, not if you allow for propellant transfer, as you should. As for crowds of anti-SLS posters: this whole site is pro-SLS by 2:1...Propellant transfer doesn't solve the problem of Mars EDL. To land humans on the surface of mars the lander needs an entry mass of 100-150mt. The percentage of a Mars lander that is fuel is not above 50 percent meaning that a Falcon Heavy could not lift one dry. In other words the unfueled mass of the lander is still too much for LVs smaller then SLS to launch into LEO. That does not mean that we need the whole 130mt of SLS with propellant transfer, the version without the upper stage may be enough. Another issue current launcher will have with getting a Mars lander into LEO will be the diameter of the heat shield. The extra fairing diameter of up to 10 or 12 meters will really simplify things compared with the 5m of currently available launchers. Mars EDL is a huge challenge. With our current technology most of Mars' surface is inaccessible and we can not put more then 1mt on the ground. I'm attaching a presentation on crewed Mars EDL if people are interested.DRM 5.0 used an EDL stage of about 60 tonnes, over 10 tonnes of which was fuel. Mass wise FH seems adequate. FH could almost certainly not lift a 12 m biconic aeroshell like DRM 5.0 used, however there are many approaches to Mars EDL and it is not obvious (to me at least) that some of these would not be possible using FH.
Its interesting that in many proposed Mars mission I read over while compiling this post a lander mass around 130mt kept showing up. Anyone want to bet where the 130mt SLS payload requirement came from?
Quote from: MikeAtkinson on 09/20/2011 08:30 amDRM 5.0 used an EDL stage of about 60 tonnes, over 10 tonnes of which was fuel. Mass wise FH seems adequate. FH could almost certainly not lift a 12 m biconic aeroshell like DRM 5.0 used, however there are many approaches to Mars EDL and it is not obvious (to me at least) that some of these would not be possible using FH.I noticed that too. That is the lander mass with out the aeroshell or payload. Integrating those three things in orbit would be a a very complex operation. I don't know what it would take to load the payload in the lander while in LEO but its hard enough to integrate a payload in a LV on Earth. All this would have to be done in zero G with only a few astronauts rather then on Earth with the benefit of plenty of equipment and people. Even if it is doable it may not be worth the draw backs compared to going ahead with SLS. Having the whole thing assembled on the ground should allow for more through testing and a simpler, safer, and likely cheaper design.
DRM 5.0 used an EDL stage of about 60 tonnes, over 10 tonnes of which was fuel. Mass wise FH seems adequate. FH could almost certainly not lift a 12 m biconic aeroshell like DRM 5.0 used, however there are many approaches to Mars EDL and it is not obvious (to me at least) that some of these would not be possible using FH.
From "Celestial Mechanics and Astrodynamics",1964, Victor Szebehely, editior, p. 56, there is a 36 hour trajectory to the Moon suggested. It's seems like a lead and shoot trajectory. Lead the Moon by a certain amount, fire off the rocket, and hit (not land, necessarily), 36 hours later.It prompted me to ask about the delta-vee penalty for flying to the Moon, basically as fast as possible.
Quote from: Robotbeat on 09/20/2011 04:25 amQuote from: notsorandom on 09/20/2011 03:19 amQuote from: mmeijeri on 09/20/2011 01:50 amQuote from: 93143 on 09/20/2011 01:38 amOne of SLS's advantages, especially for Mars, is that it can launch very large pieces (both mass-wise and size-wise) in one shot, which helps with architecture design.No, it doesn't, not if you allow for propellant transfer, as you should. As for crowds of anti-SLS posters: this whole site is pro-SLS by 2:1...Propellant transfer doesn't solve the problem of Mars EDL. To land humans on the surface of mars the lander needs an entry mass of 100-150mt....That's just plain false.If you land an empty ascent vehicle beforehand that becomes filled with ISRU-derived propellants, nothing even near 100mT is needed as an entry mass (probably could make do with just 10mT or less landed dry mass at a time...). And besides, 100mT entry mass still requires ballutes or other more difficult EDL technology.Heck, the Apollo lunar module, which could probably fit 3 in a pinch (after all, Apollo 17 had over 100kg of samples, plus the two astronauts), and had enough delta-v for a Mars ascent vehicle (if not thrust) weighed only about 4 or 5 tons dry and could have considerable weight shaved off if it used modern electronics and batteries and aluminum-lithium alloysIt also depends if you want a crew of 8 (like some of the Mars architectures had) or a smaller crew of 6, 4, or even 2 (say, for the short-stay missions... some crew could stay on orbit, ala Apollo).I spent the evening looking over a few proposed Mars missions. Haha I didn't have anything better to do. Your claim that 10mt or less could would work doesn't seem doable. DRM 5 thinks 40mt is the smallest individual piece. Mars Direct uses ISRU and it requires the ability to land 28,500 kg on the Martian surface. The habitat, power, and life support is over 10mt for a crew of four. Its something that can't really be split up into smaller pieces.That doesn't include any consumables, lab equipment, space suits, rovers, backup spares, or astronauts. A crew of four is going to require 10.4mt of consumables alone. The ISRU parts don't fit under 10mt either. For safety reasons the crew is going to need to land with plenty of consumables, a long range rover, and a habitat in case they land too far the other mission elements such as their ride home. A lot has to land with the astronauts in order to reduce the risk of an off target landing. Once again going by the Mars Direct figures that is going to be more then 10mt. The lowest mass landed element I can realistically and safely cobble together is at least 16mt from the elements in Mars Direct. I bet there was good reason to not even go that small by the study's authors. I'm not saying that the full 130mt SLS is needed for a Mars mission. However, it looks like the Falcon Heavy is too small for the job even with advanced EDL technology, ISRU, and propellant depots. Its been proposed that the core version of SLS with a 70-100mt payload and propellant depots could be the best way to go. There would need to be more study of this concept but personally I am leaning in that direction. Its interesting that in many proposed Mars mission I read over while compiling this post a lander mass around 130mt kept showing up. Anyone want to bet where the 130mt SLS payload requirement came from?
Unless you used an aeroshell or hypercone or something.
Quote from: notsorandom on 09/20/2011 07:07 amIts interesting that in many proposed Mars mission I read over while compiling this post a lander mass around 130mt kept showing up. Anyone want to bet where the 130mt SLS payload requirement came from?Some of it seems to be circular reasoning, given a 130 tonne Ares V launcher what Mars mission can we design ( DRM 5.0 ) - its not surprising it came up with requiring a 130 tonne HLV.
{snip}All the astronauts REALLY need to land with in case of an off-nominal landing is a small unpressurized rover, a couple of space suits with enough consumables to last a day or so while they drive to their landing spot. OR, you make an off-nominal landing so unlikely that those things aren't required, or that even an off-nominal landing would be within walking distance or a remote-controlled rover with enough range can be pre-landed, etc.
Quote from: notsorandom on 09/20/2011 07:07 amI spent the evening looking over a few proposed Mars missions. Haha I didn't have anything better to do. Your claim that 10mt or less could would work doesn't seem doable. DRM 5 thinks 40mt is the smallest individual piece. Mars Direct uses ISRU and it requires the ability to land 28,500 kg on the Martian surface. The habitat, power, and life support is over 10mt for a crew of four. Its something that can't really be split up into smaller pieces.That doesn't include any consumables, lab equipment, space suits, rovers, backup spares, or astronauts. A crew of four is going to require 10.4mt of consumables alone. The ISRU parts don't fit under 10mt either. For safety reasons the crew is going to need to land with plenty of consumables, a long range rover, and a habitat in case they land too far the other mission elements such as their ride home. A lot has to land with the astronauts in order to reduce the risk of an off target landing. Once again going by the Mars Direct figures that is going to be more then 10mt. The lowest mass landed element I can realistically and safely cobble together is at least 16mt from the elements in Mars Direct. I bet there was good reason to not even go that small by the study's authors. I'm not saying that the full 130mt SLS is needed for a Mars mission. However, it looks like the Falcon Heavy is too small for the job even with advanced EDL technology, ISRU, and propellant depots. Its been proposed that the core version of SLS with a 70-100mt payload and propellant depots could be the best way to go. There would need to be more study of this concept but personally I am leaning in that direction. Its interesting that in many proposed Mars mission I read over while compiling this post a lander mass around 130mt kept showing up. Anyone want to bet where the 130mt SLS payload requirement came from?Mars DRMs are not the minimum required for landing humans. I'm talking about the minimum size, not even necessarily the optimum size.So, you made lots of assumptions:1) minimum surface crew size 4 (again, no reason why 4 is the minimum required for a short-duration mission)2) precision landing can't be relied on (the lunar-roving-vehicle had a mass of only 210kg, and had a range with 2 astronauts of almost 100km... modern batteries could do better, maybe twice as long)3) the size of power, consumables (for less than 30 days), etc, can't be reduced4) Mars Direct is the best possible option for lowest mass elements (it already assumes an HLV, so if the conclusion after looking at Mars DIRECT is that you should use an HLV, you are begging the question).All the astronauts REALLY need to land with in case of an off-nominal landing is a small unpressurized rover, a couple of space suits with enough consumables to last a day or so while they drive to their landing spot. OR, you make an off-nominal landing so unlikely that those things aren't required, or that even an off-nominal landing would be within walking distance or a remote-controlled rover with enough range can be pre-landed, etc.Halving the crew could have the effect of nearly halving the minimum entry mass. We have a 6-person manned outpost right now that has crew that gets there and back with only a 3-person spacecraft. So, even if you lower the minimum crew to 2 or 3 doesn't mean your outpost can't support higher numbers. Far more important than having large numbers is getting there at all, in my opinion.
I spent the evening looking over a few proposed Mars missions. Haha I didn't have anything better to do. Your claim that 10mt or less could would work doesn't seem doable. DRM 5 thinks 40mt is the smallest individual piece. Mars Direct uses ISRU and it requires the ability to land 28,500 kg on the Martian surface. The habitat, power, and life support is over 10mt for a crew of four. Its something that can't really be split up into smaller pieces.That doesn't include any consumables, lab equipment, space suits, rovers, backup spares, or astronauts. A crew of four is going to require 10.4mt of consumables alone. The ISRU parts don't fit under 10mt either. For safety reasons the crew is going to need to land with plenty of consumables, a long range rover, and a habitat in case they land too far the other mission elements such as their ride home. A lot has to land with the astronauts in order to reduce the risk of an off target landing. Once again going by the Mars Direct figures that is going to be more then 10mt. The lowest mass landed element I can realistically and safely cobble together is at least 16mt from the elements in Mars Direct. I bet there was good reason to not even go that small by the study's authors. I'm not saying that the full 130mt SLS is needed for a Mars mission. However, it looks like the Falcon Heavy is too small for the job even with advanced EDL technology, ISRU, and propellant depots. Its been proposed that the core version of SLS with a 70-100mt payload and propellant depots could be the best way to go. There would need to be more study of this concept but personally I am leaning in that direction. Its interesting that in many proposed Mars mission I read over while compiling this post a lander mass around 130mt kept showing up. Anyone want to bet where the 130mt SLS payload requirement came from?
Quote from: MikeAtkinson on 09/20/2011 09:08 amQuote from: notsorandom on 09/20/2011 07:07 amIts interesting that in many proposed Mars mission I read over while compiling this post a lander mass around 130mt kept showing up. Anyone want to bet where the 130mt SLS payload requirement came from?Some of it seems to be circular reasoning, given a 130 tonne Ares V launcher what Mars mission can we design ( DRM 5.0 ) - its not surprising it came up with requiring a 130 tonne HLV.Looks like you may have missed something... [emphasis added]
I don't think we will use fully propulsive Mars landers. Ever tried firing a rocket into a hypersonic jet stream coming at you?
Topic Summary Posted on: Today at 03:56 AMPosted by: mmeijeri Insert QuoteIt is unlikely heavy payloads can be landed without using propulsion for substantially more than final descent and landing. Of course that doesn't mean you don't want to use aerodynamic deceleration to the maximum degree possible.
I agree that other things being equal, you can save a lot of propellant by using aerobraking, but for heavy payloads, that's not trivial. There are faring issues as well. Meanwhile, a fully propulsive Mars lander could be had more or less off the shelf if it were a beefed up Lunar lander.
Quote from: Warren Platts on 09/25/2011 12:56 pmI agree that other things being equal, you can save a lot of propellant by using aerobraking, but for heavy payloads, that's not trivial. There are faring issues as well. Meanwhile, a fully propulsive Mars lander could be had more or less off the shelf if it were a beefed up Lunar lander.Hey, I'm all for that, in fact I've advocated just that. But eventually I think both propulsive braking and aerodynamic deceleration will play substantial roles. Large single-use heatshields that require huge fairings - not so much.
Mars' gravity and atmosphere is not as great as earth, like 35-40% I think.
Jim has shown that a 10m heat shield can be folded in half to fit a 5m EELV.
Quote from: spacenut on 09/26/2011 05:19 pmJim has shown that a 10m heat shield can be folded in half to fit a 5m EELV.Only if it's a disk. The DRM 5.0 aeroshells were biconics and 10 m across.
So air braking might be just as costly as propulsive braking or landing?
IMO, the cheapest and fastest way to Mars would be a simple (as in pretty much fully propulsive), reusable (cheaper since it can be used over and over again), all chemical (faster than SEP), architecture that was evolved from previous spacecraft a la the ULA Lunar plan. Zegler et al. say their DTAL lander could easily be evolved for use on Mars. My own BOTE calculations suggest that a stretched tank DTAL lander (i.e, an ACES-71) equipped with a heat resistant titanium hull (so it could withstand the full 1 W/cm2) could land fully propulsively--no ballutes, parachutes, or heat shields required.Then the ULA MTV has a crew capacity of 16 and a nominal delta v of 11 km/sec. If there was refueling capability in Mars orbit, the ULA MTV could cut the 1-way transit times by over half compared to the Hohman transfer; if refueling was deemed impractical (probably the case for the initial missions), it would have enough delta v to do a round trip taking Hohman transfers. Again, this would all be fully propulsive--no heat shields required. The 7 hundred tonnes of propellant would only cost about $350 million, if refueled at L2 (with Lunar derived LH2/LO2). See, so the whole thing would be faster and cheaper, since it would be a simple evolution from the ULA Lunar architecture, which is itself a simple evolution from the Centaur 3rd-stage architecture.
Personally, I feel like the cheapest and most efficient way to go to mars has to make maximum use of ISRU capabilities.
I am also skeptical of the idea that a mars mission needs to bring much scientific hardware. I am not as enthusiastic about martian life as I am about, say, finding mineral ores or other industrial materials that humans can use.
We must make as our goal the settlement of mars. That is also why I favor a 1-way mission (which would also free up a lot of mass).
Quote from: constantius on 02/17/2012 10:42 pmPersonally, I feel like the cheapest and most efficient way to go to mars has to make maximum use of ISRU capabilities. Are you talking about the Moon or Mars or both?
Without going through the thread, can I just point out that the Apollo spacecraft could have gone to Mars, so any future Lunar hardware can probably be modified to being Mars capable hardware. So who's in in the best position to get men back to the Moon? Probably SpaceX.
Secondly, there is, of necessity, a fundamental difference in design between a Mars lander and a moon lander...
If you want to do ISRU on Mars, you might as well go for highest Isp LH2/LO2. ...
Quote from: Warren Platts on 02/21/2012 12:25 pmIf you want to do ISRU on Mars, you might as well go for highest Isp LH2/LO2. ...Why? CO/O2 is really easy.
1) It doesn't need to be mined and is always available on every point on the planet in unlimited quantities and requires no hard cryogenic storage. This vastly simplifies the whole project.
Quote from: Robotbeat on 02/21/2012 04:45 pm1) It doesn't need to be mined and is always available on every point on the planet in unlimited quantities and requires no hard cryogenic storage. This vastly simplifies the whole project.C. You need water anyway, so going with CO/O2 isn't going to get you out of that one. Therefore, you are merely adding an extra, unnecessary layer of duplicated effort that vastly complexifies the whole project.
Quote from: Warren Platts on 02/21/2012 04:56 pmQuote from: Robotbeat on 02/21/2012 04:45 pm1) It doesn't need to be mined and is always available on every point on the planet in unlimited quantities and requires no hard cryogenic storage. This vastly simplifies the whole project.C. You need water anyway, so going with CO/O2 isn't going to get you out of that one. Therefore, you are merely adding an extra, unnecessary layer of duplicated effort that vastly complexifies the whole project.We need water anyway, so why do we bother breathing air?
If you bold a point, it doesn't make it more important. I read it the first time.
Besides, your main point is Moon development, you barely care about going to Mars.
We need water anyway, so why do we bother breathing air?
Quote from: Robotbeat on 02/21/2012 05:24 pmWe need water anyway, so why do we bother breathing air?Extracting the hydrogen from water requires a lot of energy. ISRU equipment can use nuclear power and solar power. Plants can use sun light as a power source but animals, including humans, main source of energy is oxidising hydrocarbons. The oxygen is obtained by breathing.
C. You need water anyway, so going with CO/O2 isn't going to get you out of that one.
Quote from: Warren Platts on 02/21/2012 04:56 pmC. You need water anyway, so going with CO/O2 isn't going to get you out of that one.You need to be careful that when you make these assertions you realise that your context (long term sustainable settlement of large numbers of people, using reusable and possibly cis-lunar infrastructure) may differ from other people's.
FWIW, a great deal has been written about how to do Mars missions without having to dig for water. And, as Robotbeat has pointed out, there are huge advantages to tapping into a globally available atmospheric resource instead.
(One more point- water is available in the atmosphere, but only in very small quantities- but perhaps enough to make up for small leaks/losses in a Mars-Direct style mission.
B. You can drink it and breathe it and wash with it and grow crops with it C. You need water anyway, so going with CO/O2 isn't going to get you out of that oneF. You can run fuel cells on LH2/LO2
Bottom line: mining Martian water makes sense if and only if it's the best choice as a propellant source. Its use as a source of water for human use is barely relevant to the trades. Avoiding importing water for human use because it's "just lame" is poor engineering.
If water recycling is done well then food imported from Earth contains enough hydrogen to make up for the inevitable losses.
Food and packaging is apparently 1.83 kg/person/day (http://www.nasa.gov/audience/foreducators/stseducation/materials/Sustaining_Life.html), or 0.668 tonnes/person/year.
Importing food would only become a major nuisance once we have dozens of people on Mars at a time.
At that point we should start developing other water sources such as burning all the hydrogen-containing waste we can find and condensing water from the combustion products. Once we have more people on Mars at a time than have been in space so far in all of history then even with careful hydrogen recycling the imports may get annoying. At that point it may make sense to look at ISRU water for human use. But that's way too far in the future to affect engineering trades today!
G. You'll have a single, common fuel to run your entire cis-Martian architecture on.LH2/LO2 is the best choice. It's the engineer's choice, because it is the best chemical propellant we know about.
Quote If water recycling is done well then food imported from Earth contains enough hydrogen to make up for the inevitable losses.Do you have some numbers to back up this assertion, or is this just your intuition speaking?
Sure, there will still be water recycling: you'll need dehumidifiers to extract water out of atmosphere if nothing else, but you won't have to worry about dieing of thirst if you don't extract every last gram of H20 out of all the human feces that are produced...
The guiding philosophy that we have followed in developing the proposed sustainable exploration architecture is to use the least number of distinct elements. This meant not only all-up vehicles but the least number of main engines, avionics systems, fluids systems, ECLSS systems, etc. By keeping the many elements as common as possible development is foreshortened and costs suppressed.
No, I am not talking about "long term sustainable settlement of large numbers of people". I am talking about a modest, permanently manned research station along the lines described by Chris McKay in his address to the Mars Society. And yes, I am fully aware that this vision is quite different from the Zubrinista, fly-by-night, Mars-Direct-on-a-shoestring-style context. (snip)And what are the common elements of these missions? 100's of tonnes go up, one tiny capsule goes back. Nothing to show for the billions and billions but a box of rocks. Apollo redux on Mars, basically. A wasteful and unsustainable allocation of resources, in other words. You would think we would learn some lessons after 50 years about how not to go about things. But I guess not...
See, I just don't understand why you guys go out of your way to make life so unnecessarily hard for yourselves. The fundamental problem of Mars Direct and offspring is that they are based on the philosophy of scarcity. Everything is so starved for mass, that you willingly entertain thoughts of sifting out individual water molecules out of the thin air.
I see that you would consider an "Apollo redux" Mars mission to be worse than no mission at all. Well, on that point we will just have to differ.I don't see why you have to measure a mission by 'what comes back'. Heck, Curiosity isn't going to come back, do you think that's a mistake too?
Quote from: Warren PlattsSee, I just don't understand why you guys go out of your way to make life so unnecessarily hard for yourselves. The fundamental problem of Mars Direct and offspring is that they are based on the philosophy of scarcity. Everything is so starved for mass, that you willingly entertain thoughts of sifting out individual water molecules out of the thin air.It's more a case of 'everything is starved for cash'. Mass costs.
Your vision seems to hinge on operating RLVs on another planet. I don't doubt that this could eventually be a better way of working, just, given that we've had fifty years to get RLVs right on Earth, it's unlikely to be an easier, or a cheaper, one.
To expand a little on what 93143 said, if your MTV comes back in the exact same configuration as when you left in it, you can use it again, and thus save the cost of building another one from scratch and then launching it from Earth.
Ideally, we would like a permanently manned research station: this would minimize the $$$/man-day on Mars
That's why we've got to go beyond business as usual to find ways to bring down the cost of spaceflight. Mars Direct is the epitome of business as usual: full-up, Apollo-style flags 'n' footprints. Thus it sucks out all the oxygen in the room, and little else can be done in the meantime.
If budgets are flat, the only way to continually do more is to continually do more for less. That's why we've got to look at things like Lunar ISRU, so that we can use the resources of space itself to leverage our spaceflight capabilities.
I agree with 93143. The much weaker gravity on Moon and Mars makes the task of a SSTO LV an order of magnitude easier than a similar craft launching from Earth. Check out the DC-X; it was basically the sort of reusable, SSTO, Lunar/Mar lander that I'm talking about. Before it crashed and burned, it demonstrated a 26 hour turn-around-time, and a delta-v of 1.4 km/sec, which is 70% of the delta-v required to get to LLO.
Quote from: Warren Platts on 02/22/2012 10:10 amTo expand a little on what 93143 said, if your MTV comes back in the exact same configuration as when you left in it, you can use it again, and thus save the cost of building another one from scratch and then launching it from Earth.Yes, it's a nice idea. Just like the Orbiters were supposed to work, huh?
QuoteIdeally, we would like a permanently manned research station: this would minimize the $$$/man-day on MarsYou have to balance cost/hour (or cost/landed mass) against total program cost. In reality, the only program that has a chance of flying is one that can be met with a reasonable up-front budget. And grandiose visions of lunar propellants and Martian RLVs do not strike me as having low up-front costs.
It sounds as though your vision relies heavily on some order of magnitude reduction in the costs of operating hardware in space. I'm not holding my breath for that.
QuoteIf budgets are flat, the only way to continually do more is to continually do more for less. That's why we've got to look at things like Lunar ISRU, so that we can use the resources of space itself to leverage our spaceflight capabilities.If anything is going to 'suck the oxygen out of the room', it's a diversion to the Moon. You honestly expect it would be economically possible to create a lunar ISRU facility on a flat budget?
QuoteI agree with 93143. The much weaker gravity on Moon and Mars makes the task of a SSTO LV an order of magnitude easier than a similar craft launching from Earth. Check out the DC-X; it was basically the sort of reusable, SSTO, Lunar/Mar lander that I'm talking about. Before it crashed and burned, it demonstrated a 26 hour turn-around-time, and a delta-v of 1.4 km/sec, which is 70% of the delta-v required to get to LLO. I am well aware of the DC-X. It doesn't change the fact that operating an RLV in a hostile environment, far from any workshop facilities, and expecting it to safely carry people around, is not exactly going to be easy, and therefore not cheap either.
A Lunar propellant station would be supremely expensive: 100 to 200 $B for sure. But once it was there, the up-front cost of a Mars mission would be nil.
If anything is going to 'suck the oxygen out of the room', it's a diversion to the moon. You honestly expect it would be economically possible to create a lunar ISRU facility on a flat budget? Whose budget??
[The] path to human solar system exploration seems to be much more worthwhile and sustainable than alternatives which do not tap into Lunar propellant. [The] approach crucially depends on getting the cost of propellant production on the Moon down and on developing a space transportation system with a very long operational lifetime and minimal maintenance requirements. The former can only be tested on the Moon, while the latter should not be too hard to be achieved here on Earth. Current engines are not designed for durability, but for maximum performance. On reusable in-space systems, we have to focus on durability, at the cost of some performance.
Just tryin' to figger out what you're for.
Clearly, you're not trying to be supportive of the idea of re-usability. As it turns out, there is no law of nature which forbids mankind to build his machines so that they can be re-used.Neither, of course, is there a law of nature which forbids mankind's politicians from lying about the possible reusability of various machines, such as the Orbiters, just to pick a machine at random.
A reusable MTV would make more sense if it was a SEP or NEP device.
Quote from: Kaputnik on 03/07/2012 09:13 amA reusable MTV would make more sense if it was a SEP or NEP device.Or if it cycled between high Earth orbit and high Mars orbit instead of between low Earth orbit and low Mars orbit. That could even done by hypergolics, optionally supported by SEP just for prepositioning propellant. That would require no new technology.
Quite likely. What sort of delta-v would we be talking about?
And do you mean a high elliptical orbit, or a circular one?
As I understand it, it is quite efficient to make a OI burn during a close pass to the planet, thus benefitting from the Oberth effect and resulting in a highly elliptical orbit;
but if done at Earth you are then going to be crossing the VA belts on every orbit, which doesn't seem too clever.
Unfortunately I'm out of my depth when talking about the delta-v and the prcess required to park at a Lagrange point. Must go and read up...
Quote from: JohnFornaro on 03/07/2012 01:39 amJust tryin' to figger out what you're for.What I am interested in and supportive of is plans that strike me as realistic.
As a species we have had fifty years of messing around in space and have figured out that it's pretty hard to get right. I used to be in the "well clearly they're doing it wrong then" camp but over the years learned to temper my expectations and have a little more respect for the people in the industry who have actually achieved great things. Yes, it is frustrating...
When it comes to Mars, I tend to roll my eyeballs when a plan relies too heavily on unknowns and assumptions. What we need is simplicity, the fewest possible new hardware designs on the critical path, the greatest reliance on heritage where this is sensible. Those are the kinds of plans that get me excited, not "everybody gets a pony" ones involving moon bases and making assumptions about massive increases in budgets or reductions in launch costs.
From "Celestial Mechanics and Astrodynamics",1964, Victor Szebehely, editior, p. 56, there is a 36 hour trajectory to the Moon suggested. It's seems like a lead and shoot trajectory. Lead the Moon by a certain amount, fire off the rocket, and hit (not land, necessarily), 36 hours later.
I am all for reusability where this looks realistic and sensible. In the world today, it rarely is. Look at, for example, SeaLaunch... I don't doubt that reusability is possible, it's just that nobody has to date made it work.
In-space hardware could hopefully fare better, of course. I would fully expect that Mars surface equipment would be reused many times. Reuse of a MTV is probably doable as well. ... The capsule would ... brake into Earth orbit using a huge quantity of propellant ...A reusable MTV would make more sense if it was a SEP or NEP device.
Or if it cycled between high Earth orbit and high Mars orbit instead of between low Earth orbit and low Mars orbit. That could even done by hypergolics, optionally supported by SEP just for prepositioning propellant. That would require no new technology.
Of course, SEP and NEP are tomorrow's scaled technology, which would be usefully demonstrated and perfected in the cislunar arena.
The only thing I'd change about Martijn's suggestion is that the MTV should cycle between hi Earth orbit, say L1, and lo Mars orbit. It should be a spacecraft that is built for a fifty or more year lifetime, say, and used at least fifty times, say.
QuoteThe only thing I'd change about Martijn's suggestion is that the MTV should cycle between hi Earth orbit, say L1, and lo Mars orbit. It should be a spacecraft that is built for a fifty or more year lifetime, say, and used at least fifty times, say.Why low Mars orbit?
Perhaps it is to use the NEP/SEP for the maximum practical delta-v, thereby shifting some of the burden off the MAV.
Quote from: mmeijeri on 03/07/2012 02:17 pmQuoteThe only thing I'd change about Martijn's suggestion is that the MTV should cycle between hi Earth orbit, say L1, and lo Mars orbit. It should be a spacecraft that is built for a fifty or more year lifetime, say, and used at least fifty times, say.Why low Mars orbit?Perhaps it is to use the NEP/SEP for the maximum practical delta-v, thereby shifting some of the burden off the MAV.
Quote from: mmeijeri on 03/07/2012 02:17 pmQuote from: JFThe only thing I'd change about Martijn's suggestion is that the MTV should cycle between hi Earth orbit, say L1, and lo Mars orbit. It should be a spacecraft that is built for a fifty or more year lifetime, say, and used at least fifty times, say.Why low Mars orbit?Perhaps it is to use the NEP/SEP for the maximum practical delta-v, thereby shifting some of the burden off the MAV.
Quote from: JFThe only thing I'd change about Martijn's suggestion is that the MTV should cycle between hi Earth orbit, say L1, and lo Mars orbit. It should be a spacecraft that is built for a fifty or more year lifetime, say, and used at least fifty times, say.Why low Mars orbit?
It's not a straight-forward trade.