The assumptions are:150 passengers at 500 kg each = 75 tonnes of payloadGuesstimate transit vehicle at 25 tonnesALL vehicles are FULLY reusable from surface to surface.Mass ratios per vehicle are given by the rocket equation.

Quote from: aero on 12/20/2012 01:27 pmThe assumptions are:150 passengers at 500 kg each = 75 tonnes of payloadGuesstimate transit vehicle at 25 tonnesALL vehicles are FULLY reusable from surface to surface.Mass ratios per vehicle are given by the rocket equation.The transit vehicle will weight much more than 25 tonnes... that is the weight of a normal ISS module. Do you think you can fit 150 passengers there?? Better, name an earth vehicle where you can fit 150 passengers and weights less than 50 tonnes!

On the other hand, the passenger density of the Mars transit vehicle should be higher than that of the ISS so using the ISS as a basis will give an unrealistically high estimate of vehicle mass, IMO. I think a better estimate can be derived by scaling the Dragon Crew or the ORION capsule. Argument could be made that the Mars transit vehicle will also transport drygoods and machinery and so will be larger and heavier than just a passenger carrier. I'm looking for a low but realistic mass estimate of the transit vehicle and so want to limit it to a passenger carrier to ovoid an open ended debate about the vehicle type.

Quote from: aero on 12/20/2012 05:00 pmOn the other hand, the passenger density of the Mars transit vehicle should be higher than that of the ISS so using the ISS as a basis will give an unrealistically high estimate of vehicle mass, IMO. I think a better estimate can be derived by scaling the Dragon Crew or the ORION capsule. Argument could be made that the Mars transit vehicle will also transport drygoods and machinery and so will be larger and heavier than just a passenger carrier. I'm looking for a low but realistic mass estimate of the transit vehicle and so want to limit it to a passenger carrier to ovoid an open ended debate about the vehicle type.You can hardly have people in such cramped quarters for half a year. These are not slave transports and the transfer takes longer than sailing fom Africa to America. Also rigorous exercise is necessary for everybody to stay fit.About the fuel, maybe you turn the calculation the other way around. Assume that half of the cost (500,000$) goes for fuel. How much fuel will thay get you? How much is a metric ton of Methane/LNG at the moment?That will give you ~ an upper limit for the needed fuel, assuming the price can be achieved.

On the other hand, the passenger density of the Mars transit vehicle should be higher than that of the ISS so using the ISS as a basis will give an unrealistically high estimate of vehicle mass, IMO. I think a better estimate can be derived by scaling the Dragon Crew or the ORION capsule.

I don't have much confidence in the 150 passenger number but if the rocket equation shows that Isp is reasonable for the mass of fuel purchased from ticket revenue, then I will be more confident in the SpaceX proposal.

Quote from: aero on 12/20/2012 05:52 pmI don't have much confidence in the 150 passenger number but if the rocket equation shows that Isp is reasonable for the mass of fuel purchased from ticket revenue, then I will be more confident in the SpaceX proposal.Propellant costs will be in the noise compared to the vehicle costs.

Quote from: Jim on 12/20/2012 05:57 pmQuote from: aero on 12/20/2012 05:52 pmI don't have much confidence in the 150 passenger number but if the rocket equation shows that Isp is reasonable for the mass of fuel purchased from ticket revenue, then I will be more confident in the SpaceX proposal.Propellant costs will be in the noise compared to the vehicle costs.Jim - I know that - but I am shooting at the $500,000 ticket price, so my unrealistic assumption is that the vehicles have magically been paid for already. After fuel costs are known, and if there is a cash balance, then take out the magic and apply that balance to retire the debt.

which segment propellant costs? Earth to LEO or LEO to Mars?

What if Elon is thinking USD 500,000 for LEO-Mars (surface) one-way ticket only?

If he assumes the passenger is already on orbit (at a Bigelow's hotel, for example), the fuel need will be quite different.In a flourishing space travel market, there's room for Earth-LEO tickets, LEO-LagrangeN tickets, LEO-Moon tickets... with competing hotels/stations in each of these places -- and maybe Moon colonies. In that scenario, LEO-Mars tickets and Mars colonies would be plausible.

That would be a sematics trick. I understand that price is meant to be for the ticket Earth-Mars. If it is realistic though, I doubt.

The cheapest option looks to be to go with a Mars cycler.http://en.wikipedia.org/wiki/Mars_cyclerThat way the massive and expensive Earth to Mars transport craft can be reused multiple times and little propellant is used.Even though fuel is just a tiny fraction of the cost of a launch it becomes expensive once it's hauled up out of the gravity well.

Considering the above, I calculated the Methane/LOX fuel costs assuming a 75 tonne taxi carrying 150 passengers at 500 kg each, for a total dry mass of 150 tonnes. The fuel cost now comes out to be less than $49 million.

Quote from: aero on 12/22/2012 12:09 amConsidering the above, I calculated the Methane/LOX fuel costs assuming a 75 tonne taxi carrying 150 passengers at 500 kg each, for a total dry mass of 150 tonnes. The fuel cost now comes out to be less than $49 million. I still think 75 tonnes is too small. I would think on something over 200 tonnes dry.