Does anybody believe that in the current political environment that NASA's budget will grow along with growth in GDP?
That is why I think that the focus on a L2 or DRO gateway is essential. If it turns out that we don't have enough money for Mars, the L2 Gateway is a good fall back destination.
Furthermore, it should be easier to form international and commercial partnerships for a L2 or DRO gateway.
Quote from: yg1968 on 07/07/2014 03:01 pmThat is why I think that the focus on a L2 or DRO gateway is essential. If it turns out that we don't have enough money for Mars, the L2 Gateway is a good fall back destination.But unless it is recognized as being absolutely essential, and not just a fallback choice, I don't think it will get funded. We just don't have the money or political will to sustain 2nd choices.
Quote from: Coastal Ron on 07/07/2014 03:15 pmQuote from: yg1968 on 07/07/2014 03:01 pmThat is why I think that the focus on a L2 or DRO gateway is essential. If it turns out that we don't have enough money for Mars, the L2 Gateway is a good fall back destination.But unless it is recognized as being absolutely essential, and not just a fallback choice, I don't think it will get funded. We just don't have the money or political will to sustain 2nd choices.It's not essential for Mars. It's essential because it is the next logical step in exploration. Furthermore, it's also a middle ground for those that would prefer that we first land on the Moon prior to going to Mars.
The strange thing about this study (and the Boeing proposal) is that it leaves very little room for commercial partnerships. The only option for commercial companies is that there seems to be some pre-mission assembly of the crew/transit hab and some post-mission refurbishment of the habitats that is required at the HEO/DRO staging point. Presumably the asssembly and refurbishment could be done by commercial companies.
Quote from: yg1968 on 07/09/2014 11:41 pmThe strange thing about this study (and the Boeing proposal) is that it leaves very little room for commercial partnerships. The only option for commercial companies is that there seems to be some pre-mission assembly of the crew/transit hab and some post-mission refurbishment of the habitats that is required at the HEO/DRO staging point. Presumably the asssembly and refurbishment could be done by commercial companies.That's not surprising, NASA is basing everything on SLS and Boeing is the prime contractor for SLS. With international support and big commercial rockets in the near future, NASA can always change the plan to take advantage of these commercial services. But that depends on Congress and where they want the money spent.
The path to Mars runs through cis-lunar space and we can exploit the beneficial features of this region in a relatively low-risk environment. We also can benefit from international and commercial partnerships to prepare our hardware and gain experience for human missions beyond and on to Mars. High Earth orbits, the DRO around the Moon to which EM-1 and EM-2 will fly, and the Earth-Moon Lagrange points are all orbital locations in which deep space systems can be tested and operational procedures validated while still close enough to Earth to safely recover systems in the event of problems. Cis-lunar space is ideal for the advancement of deep space systems such as human deep space habitation.
Various international partners are interested in both robotic and human missions to the lunar surface, and NASA will likely go with them in some way. U.S. commercial entities also have interest in robotic lunar missions through NASA’s Lunar CATALYST program, which aims at enabling commercial provision of lunar landing services. NASA exploring the possibility of utilizing one of these commercial landers to place a Regolith and Environment Science and Oxygen and Lunar Volatile Extraction (RESOLVE) payload onto the lunar surface later this decade, an early test of ISRU with lunar regolith. Consistent with the GER, a web of international, NASA and commercial partnerships will yield both robotic and crewed spacecraft around and on the Moon. Additionally, many of our international partners want to send humans to the lunar surface. NASA may participate at some level, as the lunar surface affords some benefit in partial Earth-gravity operations. But NASA’s human spaceflight focus is on advancing technologies and operational experience in long-duration missions in the cis-lunar proving ground, using DRO missions, on the path that leads to Mars.
We also are laying the foundation for partnerships with both other nations and the US commercial sector. This will be an evolving roadmap; we will fill in more detail—and some major pieces—in the months and years to come as options and partnerships materialize and mature.
Mars-class missions will require crew life support for many hundreds of days at a minimum; a deep space habitation capability (hab) is critical for mission success. It is essential that the hab design receive thorough testing in a relevant deep space microgravity and high radiation environment—well before a final design and committing a crew on a Mars mission. The first deep space hab could be provided by a commercial or international partner, and could provide additional resources including power, EVA suits, stowage, science instruments, and advanced life support testing for Mars class missions as well as extend the in-space time of crewed Orion missions. The hab element also could facilitate additional docking ports to open the cis-lunar space to commercial and international missions in concert with or in addition to the Orion flights. In keeping with our space infrastructure reuse principle, a deep space hab also could provide a dual purpose, in addition to proving systems for Mars missions, by potentially serving as a staging point for lunar surface robotic science or human missions sought by our international partners. Based on the early results of orbital mechanics studies, the cis-lunar proving ground is a favorable location to test and develop the Mars class spacecraft systems prior to sending humans to pioneer Mars.
Exploration Augmentation Module Partnership: NASA is investigating concepts for deep space habitation module systems development. The deep space habitation module itself is likely to be provided by a commercial or international partner—or some hybrid of these.
What do you see as the role for commercial partnerships?They could, if we follow the ISS resupply paradigm, deliver the provisions to stock the craft with consumables. This seems to have even less ROI for a supplier than ISS, because it is not like these ships will be leaving every three months, more like ever 26 months.
Of course, several could be undergoing orbital construction at the same time. (Assuming construction is more like docking several modules together and not doing actual construction in space.)
If they build a part of the spacecraft, then it is really no different than NASA doing business with people now. If it is an integral part of the spacecraft, I should think there would be much more NASA oversight, design, and so forth than for something that only temporarily docks with the Mars Spacecraft, such as supply deliverables.
What do you see as the role for commercial partnerships?They could, if we follow the ISS resupply paradigm, deliver the provisions to stock the craft with consumables.
This seems to have even less ROI for a supplier than ISS, because it is not like these ships will be leaving every three months, more like ever 26 months.
Our current mode of construction assumes that transportation is a limitation, so we try to maximize how much we pack into construction elements. If transportation were inexpensive and available then I think we would transition to a mode of construction that more resembles what we do here on Earth - build a shell, and then fill it up and finish it onsite.With current designs of space construction that would likely mean shipping construction modules (inflatable or rigid) ready to be filled up. We did that somewhat on the ISS where the Shuttle would bring up ISPR's and other equipment to be installed.
[...] a mixture of CBM and NDS docking ports [...] a construction module could host several arms
Quote from: A_M_Swallow on 08/17/2014 03:18 am[...] a mixture of CBM and NDS docking ports [...] a construction module could host several armsI agree these could happen. I even think they probably should happen. I just don't see evidence NASA's "Evolvable Mars" planners agree with us!
Interesting interview with astronaut Al Worden. It discusses the need for a gateway among other things:http://www.americaspace.com/?p=72340
Here is a recent presentation at the January NAC (HEO Committee) meeting:http://www.nasa.gov/sites/default/files/files/2-20150112-NAC-Crusan-v6.pdfSee also this presentation by Gerst:http://www.nasa.gov/sites/default/files/files/NAC_HEO_Gerst4final-1.pdf
[...] has it 'gone dark?'
This is summary of Evolvable Mars Campaign (EMC ).[...]http://spirit.as.utexas.edu/~fiso/telecon/Craig_6-10-15/
Apparently not.Quote from: TrevorMonty on 06/11/2015 01:24 amThis is summary of Evolvable Mars Campaign (EMC ).[...]http://spirit.as.utexas.edu/~fiso/telecon/Craig_6-10-15/
Interesting, the Hybrid approach uses chemical propulsion only in the vicinity of Mars for capture and escape. I suspect that simply increasing the SEP systems mass and propellent would do these same maneuvers and replace the chemical propulsion entirely while being lower in total mass. But it would likely take longer to complete the maneuvers as they look to be making very efficient use of the Chemical propulsion where it is used.
The use of Lunar Gravity assists is almost a 3rd form of propulsion and looks very clever.
Over all the SEP system they are using looks very conservative, it's using older thrusters at modest ISP and low total power ~200 kw which is just 4x more then ARM and well below what had been considered necessary in the past for a human mission. Though it dose use a very long transit time which may not prove feasible, more advanced SEP will likely need to be employed to transit faster but most mission plans like to use what is very near term of off the shelf and optimize for low IMLEO.
Interesting way to capture, but it's pretty useless for visiting the moons or getting to the surface...
Comparing the crew transfer times of Chemical vs Hybrid:2033: 408 vs. 5992037: 637 vs. 7352041: 634 vs. 750Definitely more, but not dramatically so. I was wondering by the way, for a Martian moons mission astronauts will experience zero-g for almost 3 years. Isn't that a dealbreaker?
Quote from: redliox on 06/12/2015 09:15 amInteresting way to capture, but it's pretty useless for visiting the moons or getting to the surface...Both concepts use a crew taxi for getting to lower orbits.
There are 2 recent papers on SEP/Chemical respectively Hybrid which I think are very interesting. Maybe we can discuss them here.Mars Conjunction Crewed Missions with a Reusable Hybrid Architecture by NASA Langley, JPL et al.Combining Solar Electric Propulsion and Chemical Propulsion for Crewed Missions to Mars by NASA et al.Both are attached.
The papers only had SLS as LV no mention of commercial LVs.
Leaving the Orion behind also makes sense, why transport a heavy re enter vehicle alway to Mars and back. For same mass they can get a large habitat.
This is really quite radical considering how much Orion has been hyped as 'TEH vehicle to take us to Mars' but as soon as your looking at a reusable transit vehicle capable of parking into any kind of cis-lunar orbit the need to take the Orion beyond cis-lunar completely disappears and you only need to use it as a taxi-craft to and from the transit vehicle, a purpose for which IS reasonably well adapted for, BUT it makes using an entire SLS to launch for taxi purposes alone horribly inefficient, we could just use a smaller rocket to send Orion trans-lunar, or better yet a long-duration Dragon on FH.
Yea hauling some cargo or fuel with you would certainly help to fill out the SLS block II capacity. It gets tricky though because each mission requires both a crew delivery and a crew retrieval, and it's unlikely that you could combine-dovetail both of these into a single crew-rotation mission like we do on ISS because of the synod cycle. Do all the consumables for a mission combine to that much mass? And if we just had better SEP then wouldn't we have the time and propellent available to bring the transit vehicle to LEO and re-outfit (both propellent and crew consumables) in LEO at vastly lower cost using our Commercial launchers and ISS delivery systems.
Quote from: Impaler on 06/13/2015 07:20 pmThis is really quite radicalI'm at least glad they've acknowledged Orion is more of a dead weight for anything beyond the Moon
This is really quite radical
It gets tricky though because each mission requires both a crew delivery and a crew retrieval
I don't see why. Orion should be capable of staying in cis-lunar space for ~3 years, or not?
Quote from: Oli on 06/17/2015 06:12 amI don't see why. Orion should be capable of staying in cis-lunar space for ~3 years, or not?"~21 days maximum active crew time + ~6 months quiescent operations during lunar habitation" according to the Ames ECLSS System Engineering Workshop.
Ok...so for a Mars mission it would have needed the transfer habitat for...what exactly? Assuming there is a station in cis-lunar space, it could dock there for 3 years...or not?
Quote from: QuantumG on 06/17/2015 06:16 amQuote from: Oli on 06/17/2015 06:12 amI don't see why. Orion should be capable of staying in cis-lunar space for ~3 years, or not?"~21 days maximum active crew time + ~6 months quiescent operations during lunar habitation" according to the Ames ECLSS System Engineering Workshop.Ok...so for a Mars mission it would have needed the transfer habitat for...what exactly? Assuming there is a station in cis-lunar space, it could dock there for 3 years...or not?
There should still be regular crew missions to LDRO space station, even while a Mars mission is in progress. So rotating the Orion shouldn't be a problem. Even if there are no manned trips an unmanned replacement Orion could be used to deliver cargo using commercial LV.
However, getting to Mars is literally a long way away, both from a technical and funding standpoint. (A series of articles outlining NASA’s latest – and surprisingly expansive – Mars mission planning will be published over the coming days.)
Mr. Crusan discussed EMC plans for FY 2016. He reviewed a chart on recent accomplishments. He described the challenges involved in transporting crew and cargo to and from deep space. The SLS will be used to transport crew and cargo to cislunar space. The Orion will support crew during that trip. Commercial launch vehicles (LVs) will deliver logistics and small cargo to cislunar space. Habitation will be needed to protect and support crew in deep space for up to 60 days in cislunar and up to 1100 days in the Mars vicinity. Mr. Crusan explained that any initial, short-duration habitation module in the Proving Ground of cislunar space would serve as the initial building block required for Mars-class habitation.
Commercial LaunchUse commercial launch vehicles to deliver logistics andsmall cargo to cis-lunar spaceSmall cargo vehicle to deliver up to 11 t to TLIShroud = 5 m diameter
Common LOX/CH4 Pump-Fed Engine:Thrust: 25 klbfIsp: 355-360 sUp to 15 year lifetime150-500 s burn time5:1 throttlingNear-ZBO storage with90 K cryocoolerLOX/CH4 Pressure-Fed RCS:Thrust: 100-1000 lbf; Isp: 320 s
One thing that Crusan mentionned at the November 4 HEOC NAC meeting is that they have yet to decide if Orion will go to Mars or not. He said that there was arguments in favour of both options (Orion going to Mars or Orion not got going further than the cislunar staging point).
Quote from: yg1968 on 11/07/2015 03:35 pmOne thing that Crusan mentionned at the November 4 HEOC NAC meeting is that they have yet to decide if Orion will go to Mars or not. He said that there was arguments in favour of both options (Orion going to Mars or Orion not got going further than the cislunar staging point).I didn't think the Orion has life for 2-3yr mission see quote from Wikipedia."It is designed to support long-duration deep space missions, with up to 21 days active crew time plus 6 months quiescent.[33] During the quiescent period crew life support would be provided by another module such as aDeep Space Habitat."As returning crew I would feel lot safer reentering in a Orion that has only be in space a few weeks.
Quote from: TrevorMonty on 11/07/2015 06:10 pmQuote from: yg1968 on 11/07/2015 03:35 pmOne thing that Crusan mentionned at the November 4 HEOC NAC meeting is that they have yet to decide if Orion will go to Mars or not. He said that there was arguments in favour of both options (Orion going to Mars or Orion not got going further than the cislunar staging point).I didn't think the Orion has life for 2-3yr mission see quote from Wikipedia."It is designed to support long-duration deep space missions, with up to 21 days active crew time plus 6 months quiescent.[33] During the quiescent period crew life support would be provided by another module such as aDeep Space Habitat."As returning crew I would feel lot safer reentering in a Orion that has only be in space a few weeks.I think this is confusing requirements with capability. The capability could be greater than the requirement. An example of a system that greatly exceeded the endurance requirement is the MER rovers. What is limiting Orion to 6 months in space when it isn't supporting a crew? Radiation? Micrometeroid risk? Consumables? Seems if these are a problem, they can be fixed without adding much mass. Computers can be hardened, an Orion operating in the near Mars environment doesn't need to re-enter so shield damage might not be a problem, add more consumables to offset the leak rate, etc.Some Mars architectures require a taxi in near Mars space to ferry astronauts between the MAV and the MTV or between the MTV and a martian moon hab. Seems that Orion, having been designed to operate in cislunar space, fits these rolls well.
Quote from: ncb1397 on 11/07/2015 06:30 pmQuote from: TrevorMonty on 11/07/2015 06:10 pmQuote from: yg1968 on 11/07/2015 03:35 pmOne thing that Crusan mentionned at the November 4 HEOC NAC meeting is that they have yet to decide if Orion will go to Mars or not. He said that there was arguments in favour of both options (Orion going to Mars or Orion not got going further than the cislunar staging point).I didn't think the Orion has life for 2-3yr mission see quote from Wikipedia."It is designed to support long-duration deep space missions, with up to 21 days active crew time plus 6 months quiescent.[33] During the quiescent period crew life support would be provided by another module such as aDeep Space Habitat."As returning crew I would feel lot safer reentering in a Orion that has only be in space a few weeks.I think this is confusing requirements with capability. The capability could be greater than the requirement. An example of a system that greatly exceeded the endurance requirement is the MER rovers. What is limiting Orion to 6 months in space when it isn't supporting a crew? Radiation? Micrometeroid risk? Consumables? Seems if these are a problem, they can be fixed without adding much mass. Computers can be hardened, an Orion operating in the near Mars environment doesn't need to re-enter so shield damage might not be a problem, add more consumables to offset the leak rate, etc.Some Mars architectures require a taxi in near Mars space to ferry astronauts between the MAV and the MTV or between the MTV and a martian moon hab. Seems that Orion, having been designed to operate in cislunar space, fits these rolls well.Since the current Orion design is for cis-lunar operations, taking it to Mars would require an upgrade, probably expensive. Simpler to use the current design and not take it to Mars, especially with a reusable interplanetary vehicle that can return to cis-lunar space.Now if there is a requirement to ferry crew in Mars orbit, then it would make sense to use an upgraded Orion instead of developing another vehicle.
I don't see why we can't have several variants of Orion
...and if we do need the ability to ferry crew in Mars orbit it makes a lot of sense to have Orion be that vehicle.
Refueling makes it feasible for one vehicle to serve multiple roles.
Quote from: Robotbeat on 11/11/2015 02:39 amRefueling makes it feasible for one vehicle to serve multiple roles.But the goal here is to reduce the amount of mass that has to be accelerated and decelerated, dropped into gravity wells and boosted out again, thereby reducing the amount of fuel that is needed in the first place.
Why are we focused on reducing amount of fuel? Is fuel really a good stand-in for cost, especially when much of it at the end will be picked up at the destination?
It makes no sense to haul a heatshield around in deep space. It is a waste of propellant to haul it halfway across the solar system and back just so that you'll have it when you return to Earth.
Quote from: Coastal Ron on 11/10/2015 09:18 pmIt makes no sense to haul a heatshield around in deep space. It is a waste of propellant to haul it halfway across the solar system and back just so that you'll have it when you return to Earth.You are assuming that the MTV performs a propulsive capture at Earth, so it can be used again. Once you've done that, you can rendezvous with your reentry capsule. It does make sense to haul a heatshield around in deep space if that mass replaces the prop to do that dV for the capture, IE you allow the MTV to be expended. Cheers, Martin
Quote from: Robotbeat on 11/11/2015 03:34 amWhy are we focused on reducing amount of fuel? Is fuel really a good stand-in for cost, especially when much of it at the end will be picked up at the destination?Well phrased! Picking up propellant anywhere along the way breaks the tyranny of the rocket equation.There's another tyranny, though: funding. I hope NASA is learning the secrets to break that tyranny as well. The current SLS approach is to trickle dollars at all the "right" suppliers. (As an example, I think dollars are still trickling towards Orbital/ATK for "risk reduction" research into advanced solid propellants. But the trickle is so small it gets little or no notice.)Regarding Orion and Mars, I predict we will see NASA trickle dollars towards Lockheed Martin, asking them to do "risk reduction" on Orion-derived vehicles. Perhaps a capsule with a better heat shield, or a variant with no heat shield, etc.
Quote from: Coastal Ron on 11/10/2015 09:18 pmIt makes no sense to haul a heatshield around in deep space. It is a waste of propellant to haul it halfway across the solar system and back just so that you'll have it when you return to Earth.You are assuming that the MTV performs a propulsive capture at Earth, so it can be used again. Once you've done that, you can rendezvous with your reentry capsule. It does make sense to haul a heatshield around in deep space if that mass replaces the prop to do that dV for the capture, IE you allow the MTV to be expended.
Quote from: sdsds on 11/11/2015 04:12 amQuote from: Robotbeat on 11/11/2015 03:34 amWhy are we focused on reducing amount of fuel? Is fuel really a good stand-in for cost, especially when much of it at the end will be picked up at the destination?Well phrased! Picking up propellant anywhere along the way breaks the tyranny of the rocket equation.There's another tyranny, though: funding. I hope NASA is learning the secrets to break that tyranny as well. The current SLS approach is to trickle dollars at all the "right" suppliers. (As an example, I think dollars are still trickling towards Orbital/ATK for "risk reduction" research into advanced solid propellants. But the trickle is so small it gets little or no notice.)Regarding Orion and Mars, I predict we will see NASA trickle dollars towards Lockheed Martin, asking them to do "risk reduction" on Orion-derived vehicles. Perhaps a capsule with a better heat shield, or a variant with no heat shield, etc.Agreed, very likely Lockheed Martin will get some funding to research an Orion based taxi. I think it's definitely worth looking into and seeing what the options are.
Unfortunately, modifying Orion for refueling (necessary for this sort of thing to be worthwhile, IMHO) sounds difficult from what Orion people have told me. Although honestly, I think the idea of refueling to them is pretty new... they haven't really considered it! Thus it may not be that bad.
I don't believe the Orion Crew Module Adapter (CMA) provides any way to transfer propellant between the Crew Module and the Service Module. But I suppose the Crew Module's RCS propellant supply could be refilled by transfer through the docking adapter....(If anyone wants to assert the CMA does facilitate propellant transfer between the modules, I'd love to be corrected with a source citation!)
Quote from: MP99 on 11/11/2015 06:49 amQuote from: Coastal Ron on 11/10/2015 09:18 pmIt makes no sense to haul a heatshield around in deep space. It is a waste of propellant to haul it halfway across the solar system and back just so that you'll have it when you return to Earth.You are assuming that the MTV performs a propulsive capture at Earth, so it can be used again. Once you've done that, you can rendezvous with your reentry capsule. It does make sense to haul a heatshield around in deep space if that mass replaces the prop to do that dV for the capture, IE you allow the MTV to be expended. Cheers, MartinOr you return the crew through aerobraking and the MTV eventually maneuvers to capture into Earth orbit through SEP. You pretty much have to use chemical for capture to get the crew down in an expedited fashion otherwise
Quote from: ncb1397 on 11/11/2015 11:25 amQuote from: MP99 on 11/11/2015 06:49 amQuote from: Coastal Ron on 11/10/2015 09:18 pmIt makes no sense to haul a heatshield around in deep space. It is a waste of propellant to haul it halfway across the solar system and back just so that you'll have it when you return to Earth.You are assuming that the MTV performs a propulsive capture at Earth, so it can be used again. Once you've done that, you can rendezvous with your reentry capsule. It does make sense to haul a heatshield around in deep space if that mass replaces the prop to do that dV for the capture, IE you allow the MTV to be expended. Cheers, MartinOr you return the crew through aerobraking and the MTV eventually maneuvers to capture into Earth orbit through SEP. You pretty much have to use chemical for capture to get the crew down in an expedited fashion otherwiseSo, you're saying it makes sense to carry the heatshield even if the MTV is recovered by SEP? Cheers, Martin
Quote from: MP99 on 11/14/2015 08:28 amQuote from: ncb1397 on 11/11/2015 11:25 amQuote from: MP99 on 11/11/2015 06:49 amQuote from: Coastal Ron on 11/10/2015 09:18 pmIt makes no sense to haul a heatshield around in deep space. It is a waste of propellant to haul it halfway across the solar system and back just so that you'll have it when you return to Earth.You are assuming that the MTV performs a propulsive capture at Earth, so it can be used again. Once you've done that, you can rendezvous with your reentry capsule. It does make sense to haul a heatshield around in deep space if that mass replaces the prop to do that dV for the capture, IE you allow the MTV to be expended. Or you return the crew through aerobraking and the MTV eventually maneuvers to capture into Earth orbit through SEP. You pretty much have to use chemical for capture to get the crew down in an expedited fashion otherwiseSo, you're saying it makes sense to carry the heatshield even if the MTV is recovered by SEP? I'm saying that the the MTV does a transfer for a near miss with Earth. A few days before the Earth pass, crew loads up in Orion and does a divert with the service module to interception with Earth. The heat shield is useful here because it is used in place of propellant...
Quote from: ncb1397 on 11/11/2015 11:25 amQuote from: MP99 on 11/11/2015 06:49 amQuote from: Coastal Ron on 11/10/2015 09:18 pmIt makes no sense to haul a heatshield around in deep space. It is a waste of propellant to haul it halfway across the solar system and back just so that you'll have it when you return to Earth.You are assuming that the MTV performs a propulsive capture at Earth, so it can be used again. Once you've done that, you can rendezvous with your reentry capsule. It does make sense to haul a heatshield around in deep space if that mass replaces the prop to do that dV for the capture, IE you allow the MTV to be expended. Or you return the crew through aerobraking and the MTV eventually maneuvers to capture into Earth orbit through SEP. You pretty much have to use chemical for capture to get the crew down in an expedited fashion otherwiseSo, you're saying it makes sense to carry the heatshield even if the MTV is recovered by SEP?
Quote from: MP99 on 11/11/2015 06:49 amQuote from: Coastal Ron on 11/10/2015 09:18 pmIt makes no sense to haul a heatshield around in deep space. It is a waste of propellant to haul it halfway across the solar system and back just so that you'll have it when you return to Earth.You are assuming that the MTV performs a propulsive capture at Earth, so it can be used again. Once you've done that, you can rendezvous with your reentry capsule. It does make sense to haul a heatshield around in deep space if that mass replaces the prop to do that dV for the capture, IE you allow the MTV to be expended. Or you return the crew through aerobraking and the MTV eventually maneuvers to capture into Earth orbit through SEP. You pretty much have to use chemical for capture to get the crew down in an expedited fashion otherwise
Quote from: ncb1397 on 11/14/2015 07:22 pmQuote from: MP99 on 11/14/2015 08:28 amQuote from: ncb1397 on 11/11/2015 11:25 amQuote from: MP99 on 11/11/2015 06:49 amQuote from: Coastal Ron on 11/10/2015 09:18 pmIt makes no sense to haul a heatshield around in deep space. It is a waste of propellant to haul it halfway across the solar system and back just so that you'll have it when you return to Earth.You are assuming that the MTV performs a propulsive capture at Earth, so it can be used again. Once you've done that, you can rendezvous with your reentry capsule. It does make sense to haul a heatshield around in deep space if that mass replaces the prop to do that dV for the capture, IE you allow the MTV to be expended. Or you return the crew through aerobraking and the MTV eventually maneuvers to capture into Earth orbit through SEP. You pretty much have to use chemical for capture to get the crew down in an expedited fashion otherwiseSo, you're saying it makes sense to carry the heatshield even if the MTV is recovered by SEP? I'm saying that the the MTV does a transfer for a near miss with Earth. A few days before the Earth pass, crew loads up in Orion and does a divert with the service module to interception with Earth. The heat shield is useful here because it is used in place of propellant...Originally when I brought this up it was not necessarily to debate the overall energy requirements of slowing down for Earth orbit or doing a direct entry with a single vehicle that had a heatshield.The more important issue is that if we know that we will be wanting vehicles that can return more than 4-6 people at a time from Mars (the size of the current Orion), then we should start working on that now. We know SpaceX is, since their MCT is a reusable vehicle that will supposedly carry far more than 6 people at a time. Not that it means they have solved the problem, only that they have decided they don't want to be limited by what the Orion transportation capabilities are.I would imagine the eventual solution will involve either fuel or time, or both. For instance, it could be that some form of SEP will be used by a vehicle returning from Mars to be captured by the Earth-Moon system, but that it will take time (i.e. weeks, months) in order to ultimately slow down and enter LEO when the passengers will be able to transfer to something like the upcoming Commercial Crew vehicles. Or maybe the system will use chemical propulsion and do it much quicker, but it would obviously need to have a higher logistics requirement to maintain that type of system if it's used a lot.So while Orion could be used, it's too limiting by itself to expand humanity out beyond Earth. We'll need something different, something better.
Quote from: Coastal Ron on 11/14/2015 07:41 pm...So while Orion could be used, it's too limiting by itself to expand humanity out beyond Earth. We'll need something different, something better.We haven't even landed one person yet. That is the first step before we start thinking about the engineering to move a million. IMO it isn't NASA's job to colonize Mars.
...So while Orion could be used, it's too limiting by itself to expand humanity out beyond Earth. We'll need something different, something better.
It is NASA's job to push the frontiers of the art of the possible. They can show that you can land on the moon and return him back to earth. They can show that you can grow food in Mars soil and live there for a long time.
Let SpaceX do what they are doing and NASA do what they are doing. They don't have to be doing the same thing. Maybe their MCT works better, maybe NASA's system does. I wouldn't put all my eggs in one basket though.
PDF of all the Mars Manned Landing Sites Presentationshttp://www.nasa.gov/sites/default/files/atoms/files/mars-c-abstracts_in_order_of_presentation10242015_0.pdf
Quote from: philw1776 on 12/21/2015 06:13 pmPDF of all the Mars Manned Landing Sites Presentationshttp://www.nasa.gov/sites/default/files/atoms/files/mars-c-abstracts_in_order_of_presentation10242015_0.pdfI've read and heard more about planetary protection recently (for example on thespaceshow) and I think that's going to be a huge issue for manned missions. In fact it looks like there's no way around teleoperation of robotic assets since the regions you want to explore are exactly the ones that need protection. The question then is of course why land at all.
My understanding of orbital mechanics is quite limited. I think a high circular orbit is expensive delta-v wise. Elliptical orbit would be ok but does make rendezvous more restricted. Also would Phobos and Deimos interfere with elliptical orbits, small as they are?
18 tonnes payload to Mars.Transfer between deep retrograde lunar orbit and lunar distance high earth orbit before departure and after arrival in cis-lunar space.This takes up to 200 days, leaving 15 - 200 days for resupply.Crewed missions take 3 Orion (1 for hybrid propulsion stage refurb).2 SLS per year. Crew every other synod.3rd manned mission returns in 2046.No evolution of SLS, Orion, hybrid propulsion stage, or any other system. So optimized that it is hard to see if the evolution of any one element would improve the overall system.32 SLS gives 3600 man-days on Mars. Long gap between crews. Approx. 1.5 martian years.
They need a reusable lander (Hercules is what they call it) to enable a continual presence. Adding more ISRU then allows a build-up of crew to about 16.
No evolution of SLS, Orion, hybrid propulsion stage, or any other system.
The refuelling tankers are sized for SLS but could be made smaller to enable commercial LVs to be used.
Quote from: Zed_Noir on 06/03/2016 11:36 pmQuote from: TrevorMonty on 06/03/2016 08:49 pmThey still need SLS for crew and larger payloads, especially its 8M fairing. Adding commercial LVs to mix should make it more affordable and keep SLS launches to 1-2 a year.Actually it will be zero if the commercial Colonial fleet materialize by about 2025. Can we NOT bring SpaceX into this?
Quote from: TrevorMonty on 06/03/2016 08:49 pmThey still need SLS for crew and larger payloads, especially its 8M fairing. Adding commercial LVs to mix should make it more affordable and keep SLS launches to 1-2 a year.Actually it will be zero if the commercial Colonial fleet materialize by about 2025.
They still need SLS for crew and larger payloads, especially its 8M fairing. Adding commercial LVs to mix should make it more affordable and keep SLS launches to 1-2 a year.
Quote from: Dalhousie on 06/04/2016 02:14 amQuote from: Zed_Noir on 06/03/2016 11:36 pmQuote from: TrevorMonty on 06/03/2016 08:49 pmThey still need SLS for crew and larger payloads, especially its 8M fairing. Adding commercial LVs to mix should make it more affordable and keep SLS launches to 1-2 a year.Actually it will be zero if the commercial Colonial fleet materialize by about 2025. Can we NOT bring SpaceX into this?There are probably people at NASA asking that exact same question!