In the context of Red Dragon there will be no possibility of "waving off" the first landing attempt: direct entry is a given; whatever conditions exist (atmospheric, surface or vehicular) at the time of Mars approach are the conditions under which landing must be attempted.Is it fair to ask whether that particular landing paradigm is really the one SpaceX wants to develop and use in perpetuity? Loss of Mission because a low probability condition occurred is a risk that robotic missions can carry. Human spaceflight missions will have a more difficult time with a landing paradigm like that. The solution (ISTM) will be to develop with robotic precursor missions a paradigm for Mars approach and landing that allows for the possibility that adverse conditions might temporarily exist at the time of first approach. A paradigm that allows for a second chance a few days later could not only save a mission but also save the lives of crew!Clearly I am suggesting SpaceX could attempt aerocapture followed by subsequent aerobraking and landing.Connecting the dots: that allows for the terrain relative navigation option.
With the change of a dust storm it could take weeks or months to clear. Once Dragon's it's dropped the service module it will have only a few hours before it runs out of power.I guess aerobraking with the panels still attached is possibility
Quote from: Dalhousie on 03/20/2017 05:28 AMWith the change of a dust storm it could take weeks or months to clear. Once Dragon's it's dropped the service module it will have only a few hours before it runs out of power.I guess aerobraking with the panels still attached is possibilityGood points! I'm dubious about aerobraking with panels attached and thus think the Dragon design isn't likely to go forward as the Mars landing design of choice.For Red Dragon I would want them to have a sensor-guided navigation landing mode and a backup inertial-guided mode as well. I'd want that regardless of whether the sensor-guided mode was using Martian GPS or optical terrain-relative navigation.
Quote from: FutureSpaceTourist on 03/18/2017 10:04 PMCross-posting as shows some on-going Red Dragon work, although discussion of landing site specifics probably best in original landing site thread:Quote from: FutureSpaceTourist on 03/18/2017 09:40 PMQuotePaul Wooster, SpaceX, on Mars landing site selection: looking at sites at latitudes < 40˚, elevation as low as possible. #LPSC2017https://twitter.com/jeff_foust/status/843229275025227777QuoteWooster: identified several candidate sites, but many likely too rocky. Arcadia region looks promising. #LPSC2017https://twitter.com/jeff_foust/status/843229571642286081Edit: from context I think he's talking about Red Dragon landing siteThere's no paper by Wooster listed at LPSC which starts tomorrow. Some sort of pre-conference event?Arcadia is about as flat as they come, would looking like the Viking 2 landing site but perhaps less rocky (there is no medium sized crater nearby). Very boring, but probably with shallow subsurface ice.
Cross-posting as shows some on-going Red Dragon work, although discussion of landing site specifics probably best in original landing site thread:Quote from: FutureSpaceTourist on 03/18/2017 09:40 PMQuotePaul Wooster, SpaceX, on Mars landing site selection: looking at sites at latitudes < 40˚, elevation as low as possible. #LPSC2017https://twitter.com/jeff_foust/status/843229275025227777QuoteWooster: identified several candidate sites, but many likely too rocky. Arcadia region looks promising. #LPSC2017https://twitter.com/jeff_foust/status/843229571642286081Edit: from context I think he's talking about Red Dragon landing site
QuotePaul Wooster, SpaceX, on Mars landing site selection: looking at sites at latitudes < 40˚, elevation as low as possible. #LPSC2017https://twitter.com/jeff_foust/status/843229275025227777QuoteWooster: identified several candidate sites, but many likely too rocky. Arcadia region looks promising. #LPSC2017https://twitter.com/jeff_foust/status/843229571642286081Edit: from context I think he's talking about Red Dragon landing site
Paul Wooster, SpaceX, on Mars landing site selection: looking at sites at latitudes < 40˚, elevation as low as possible. #LPSC2017
Wooster: identified several candidate sites, but many likely too rocky. Arcadia region looks promising. #LPSC2017
The SHARAD radar on MRO indicates potential ice deposits in Arcadia a few meters below the surface. They might be too deep for Red Dragon to drill down to but there are ways it could confirm the ice is there without having to do so.
Green: delay of first Red Dragon mission to 2020 opens opportunity to fly a NASA experiment on that mission. #LPSC2017
How much do duststorms obscure sight really? How low would a lander need to go before getting sight of the terrain? This should be known from observations by the rovers. In the worst of the worst dust storms or with sufficiently high probability to ignore the risk?
Quote from: guckyfan on 03/20/2017 06:50 PMHow much do duststorms obscure sight really? How low would a lander need to go before getting sight of the terrain? This should be known from observations by the rovers. In the worst of the worst dust storms or with sufficiently high probability to ignore the risk?From orbit, they can obscure the surface completely. On the surface I think visibility drops to a km km - it's like a thick smog. I would also worry about contrast effects. The landmarks might be still visible by the contrast might be so low that the system cannot recognise them.Of course the proposed landing site is so flat that there are unlikely to be many useful landmarks anyway.
Quote from: notsorandom on 03/20/2017 04:30 PMThe SHARAD radar on MRO indicates potential ice deposits in Arcadia a few meters below the surface. They might be too deep for Red Dragon to drill down to but there are ways it could confirm the ice is there without having to do so.Meteorite impacts have exposed ice at ~1 m depths at this sort of latitude as I understand.
Quote from: Dalhousie on 03/20/2017 09:06 PMQuote from: notsorandom on 03/20/2017 04:30 PMThe SHARAD radar on MRO indicates potential ice deposits in Arcadia a few meters below the surface. They might be too deep for Red Dragon to drill down to but there are ways it could confirm the ice is there without having to do so.Meteorite impacts have exposed ice at ~1 m depths at this sort of latitude as I understand.Here is an interesting presentation talking about the radar and the terraced impact craters in the area indicating subsurface ice.