Point to point is best served with ground based transport... IMHO...Look at the Crawlers pulling sleds overland near the south pole, for an earth bound example... Or the Alaska Highway circa 1950's using trucks and crawlers... as another... Electric Drive machines to build and maintain unpaved roads between bases and mines...Electric Drive transports to travel the roads with people and materials...From a least cost and least trouble to get going standpoint... This is the best early way to move TONS around Mars...My opinion...
I wonder if the accurate Earth point-to-point relies on GPS? If so, accurate Mars p2p might be difficult?
Quote from: freda on 12/08/2017 07:17 pmI wonder if the accurate Earth point-to-point relies on GPS? If so, accurate Mars p2p might be difficult?No. If a Martian GPS system is not ready in time for Mars P2P. Then terrain contour-matching navigation with radar should suffice. The technology is quite mature. The USAF use it with their cruise missiles since the early 80's.
It might be a good idea initially, but eventually a good ground transportation system would be needed. Hyperloop would probably be best as it would not be affected by Martian dust storms, hub to hub. All terrain electric ground rovers and trains may come first. BFS would probably require too much fuel to process unless traveling half way around Mars.
Quote from: spacenut on 12/08/2017 06:59 pmIt might be a good idea initially, but eventually a good ground transportation system would be needed. Hyperloop would probably be best as it would not be affected by Martian dust storms, hub to hub. All terrain electric ground rovers and trains may come first. BFS would probably require too much fuel to process unless traveling half way around Mars. Hyperloop on Mars wouldn't require tubes. That is why it is being developed and operated at a half percent of an atmosphere.
Was wondering if BFS could be used for sub-orbital hops around Mars delivering people and cargo to different sites on Mars. With just the header tanks full and a mostly full cargo hold (say 100 tons) how many hops could it make on Mars?
Quote from: spacenut on 12/08/2017 06:59 pmIt might be a good idea initially, but eventually a good ground transportation system would be needed. Hyperloop would probably be best as it would not be affected by Martian dust storms, hub to hub. All terrain electric ground rovers and trains may come first. BFS would probably require too much fuel to process unless traveling half way around Mars. One possible solution replace the vacuum Raptors with BNTR engines and use liquefied CO2 as the primary propellant.When it lands the engines operate in power reactor mode and recharge the tanks with Martian CO2.The ISP would not be great but it would be good enough for sub orbital hops on Mars and probably could even achieve orbit.
Since BFS can deliver according to Musk about 1/4th it's to Mars payload upon return to Earth, looking at delta V, BFS could do Mars ptp and return with around that payload both ways. In other words, the entire planet would be accessible.
Quote from: AncientU on 12/08/2017 11:13 pmQuote from: spacenut on 12/08/2017 06:59 pmIt might be a good idea initially, but eventually a good ground transportation system would be needed. Hyperloop would probably be best as it would not be affected by Martian dust storms, hub to hub. All terrain electric ground rovers and trains may come first. BFS would probably require too much fuel to process unless traveling half way around Mars. Hyperloop on Mars wouldn't require tubes. That is why it is being developed and operated at a half percent of an atmosphere.I am not talking 20 or 30 years after colonization begins. Before you build a hyperloop you need somewhere to go. I am thinking 1 settlement and maybe a scattering of outposts. Can a BFR carry enough water to make it worthwhile?
Yes but you have to get them to mars first... On the 1st expedition to Mars musk said it will consist of 4 cargo and 2 passenger BFS's. Once you unload the cargo ships they would be immediately available for use. Why not use them? And what about the drivers? Crossing thousands of miles of Martian desert in a crawler would be a very dangerous thing to do.
Quote from: philw1776 on 12/09/2017 12:59 pmSince BFS can deliver according to Musk about 1/4th it's to Mars payload upon return to Earth, looking at delta V, BFS could do Mars ptp and return with around that payload both ways. In other words, the entire planet would be accessible.That is a pretty good start. That could be useful for substantial crewed missions to anywhere on the planet. No longer a "mission per synod" situation. You are getting vastly better use from your BFS then, same as around earth. It is the travel time that cuts into it's reuse.Anyone prepared to estimate the one way p2p cargo tonnage, if you bring the empty BFS back without refuelling?That could be very useful for setting up a new base, maybe not self sufficient but eg a thorium mine like mentioned above. Or maybe you are just transporting a whole bunch of startup prospecting equipment, from an existing base that no longer needs it, to investigate a new location.
I assume a good early unmanned Mars exploration program would require that a BFS on Mars next to a propellant plant must be able to launch, land at some other point on Mars, then relaunch, land back near the propellant plant and automatically reattach itself.
Quote from: KelvinZero on 12/09/2017 03:33 pmQuote from: philw1776 on 12/09/2017 12:59 pmSince BFS can deliver according to Musk about 1/4th it's to Mars payload upon return to Earth, looking at delta V, BFS could do Mars ptp and return with around that payload both ways. In other words, the entire planet would be accessible.That is a pretty good start. That could be useful for substantial crewed missions to anywhere on the planet. No longer a "mission per synod" situation. You are getting vastly better use from your BFS then, same as around earth. It is the travel time that cuts into it's reuse.Anyone prepared to estimate the one way p2p cargo tonnage, if you bring the empty BFS back without refuelling?That could be very useful for setting up a new base, maybe not self sufficient but eg a thorium mine like mentioned above. Or maybe you are just transporting a whole bunch of startup prospecting equipment, from an existing base that no longer needs it, to investigate a new location.Off to a Christmas party soon so can't build a spreadsheet model but based on a quick look at existing spreadsheets I'd say a couple hundred tonnes to anywhere with tiny return payload. Plenty. Getting to Mars orbital velocity requires ~4Km/sec Delta V which lets you go pretty much anywhere. Need another 4 Km/sec back but no couple hundred tonnes payload. BFS can do roughly 7Km/sec with a 200 T payload.Gonna be a long time before mines needed for thorium assuming you have the non-existant reactors; easier to hall the minimal thorium mass from Earth than to set up a remote mining base.Again the gating factor is energy to produce the 1100+ tonnes of propellant per round trip flight. For the first several synods it's all about producing enough to get the BFSs back to The Green Hills of Earth. A BIG challenge.
I apologize and retract my statement about P2P and return capability. I realized last night that I did not account for the Km/sec needed for the landing burns each way. Unlike Earth where the atmosphere slows the BFS down to under 0.2 Km/sec and minimal propellant is needed for landing, Mars' atmosphere provides some but far less reduction in velocity. If I can get a good # for the terminal velocity of a craft re-entering from Mars orbit, I could be more specific about the BFS but I no longer believe it can do P2P and back to anywhere on Mars. Sorry for posting mis-information.
I am thinking more of a takeoff from the main base empty of cargo. Land at an outpost and load up with water as a cargo and return with it to the main base without refueling. How many km/sec would be required for a suborbital hop of say, 2000 miles? How much cargo can it bring back to base without refueling?
Quote from: Steve D on 12/11/2017 02:32 amI am thinking more of a takeoff from the main base empty of cargo. Land at an outpost and load up with water as a cargo and return with it to the main base without refueling. How many km/sec would be required for a suborbital hop of say, 2000 miles? How much cargo can it bring back to base without refueling?You'd spend more water making propellant for the flight than you could bring back. Pointless.
Hi Steve, I can't do the numbers, but given the BFS tanks take something like a 1000 tons and the typical payload discussed is in the 50 to 200 ton range, Im not sure it could even carry enough in a one way trip. The cargo you could carry on the second leg of a two way trip without refueling just has to be far far worse even than that.I don't think anyone has been debating the assumption that the absolute #1 requirement for the main base is an access to water, so that the BFS can return home. This was certainly very clear in Elon Musk's presentation.You may be unaware of how much evidence there is for water on mars, even quite near the equator. As a last resort we might even be able to extract it from the atmosphere.https://en.wikipedia.org/wiki/Water_on_Mars
Chemistry makes flying a BFS elsewhere to haul back water is a losing proposition. Takes roughly 9Kg water to yield 1Kg of hydrogen. In other words haul back 90 tonnes of water and get 10 tonnes of hydrogen. You spent a couple hundred tonnes of methane CH4 to do this.
Quote from: KelvinZero on 12/11/2017 04:08 pmHi Steve, I can't do the numbers, but given the BFS tanks take something like a 1000 tons and the typical payload discussed is in the 50 to 200 ton range, Im not sure it could even carry enough in a one way trip. The cargo you could carry on the second leg of a two way trip without refueling just has to be far far worse even than that.I don't think anyone has been debating the assumption that the absolute #1 requirement for the main base is an access to water, so that the BFS can return home. This was certainly very clear in Elon Musk's presentation.You may be unaware of how much evidence there is for water on mars, even quite near the equator. As a last resort we might even be able to extract it from the atmosphere.https://en.wikipedia.org/wiki/Water_on_MarsLots of evidence yes, but until you get your hands on it...... Just trying to see what options the first crews will have if abundant water is not found where they land. I am assuming the first 6 BFSs will not be carrying autonomous electric powered water tanker trucks. What they will have are 4 cargo ships that when emptied could carry large amounts of cargo. If a good source of water is found at a distance that is too far for whatever rovers they have could handle, could a BFS be used for that? I am assuming a suborbital hop would not need full fuel tanks on the BFS. After all it is capable of returning to earth without refueling.