Quote from: guckyfan on 12/03/2015 07:52 amI have thought of a fully refueled tanker and a fully fueled MCT going to TLI together. The tanker then transfers its fuel to the MCT and does a direct return to earth while the MCT goes to land and relaunch from the moon. It's the most fuel efficient mission profile. The tricky part is rendezvous and refuelling on the way to the moon.Obviously you dual launched the MCT and the tanker from a couple of nearby launch facilities at the same time. Unless you think there will only be one launch pad for the BFR.
I have thought of a fully refueled tanker and a fully fueled MCT going to TLI together. The tanker then transfers its fuel to the MCT and does a direct return to earth while the MCT goes to land and relaunch from the moon. It's the most fuel efficient mission profile. The tricky part is rendezvous and refuelling on the way to the moon.
Quote from: Zed_Noir on 12/03/2015 07:28 amQuote from: Impaler on 12/02/2015 08:04 pm...In any event this type of lunar mission, even without crew would be an excellent shake-down mission for the MCT as it would duplicate many of the aspects of a Mars mission.Have you consider using unmanned MCT tankers in LEO and LLO to top off the MCT lunar lander's prop tanks? In case of LLO for both descent & ascent from the Lunar surface.No that would be very inefficient. The MCT has a 75 mt dry mass which would be moved all the way to LLO to do a job that could easily be done by a mere tank with a ~5% dry mass fraction. I would put that tank on a SEP tug which is how both the propellants and MCT will be moved from LEO to the staging point for the lunar landing.If we need more propellant then I would just move the staging point closer to the moon as I described, this easily brings the cargo delivery mass to over the 100 mt design goal and the MCT will almost have a volume limit just like every vehicle which means we can't just arbitrarily increase useful cargo even if we have the DeltaV to push it on paper it still needs to fit into the vehicle.Speculation about 'MCT Tanker' is in my opinion misguided, the vehicle would be a terrible tanker due to it's dry mass which is highly specialized for other functions. The LEO tanker will be a stretched 2nd stage which will transfer propellant to SEP tugs which will move propellants beyond LEO.
Quote from: Impaler on 12/02/2015 08:04 pm...In any event this type of lunar mission, even without crew would be an excellent shake-down mission for the MCT as it would duplicate many of the aspects of a Mars mission.Have you consider using unmanned MCT tankers in LEO and LLO to top off the MCT lunar lander's prop tanks? In case of LLO for both descent & ascent from the Lunar surface.
...In any event this type of lunar mission, even without crew would be an excellent shake-down mission for the MCT as it would duplicate many of the aspects of a Mars mission.
Quote from: Zed_Noir on 12/03/2015 10:02 amQuote from: guckyfan on 12/03/2015 07:52 amI have thought of a fully refueled tanker and a fully fueled MCT going to TLI together. The tanker then transfers its fuel to the MCT and does a direct return to earth while the MCT goes to land and relaunch from the moon. It's the most fuel efficient mission profile. The tricky part is rendezvous and refuelling on the way to the moon.Obviously you dual launched the MCT and the tanker from a couple of nearby launch facilities at the same time. Unless you think there will only be one launch pad for the BFR. They can take a month or two to launch and refuel both in LEO, just the way they would assemble a Mars fleet to launch into a launch window. What's the problem?
Quote from: guckyfan on 12/03/2015 10:24 amThey can take a month or two to launch and refuel both in LEO, just the way they would assemble a Mars fleet to launch into a launch window. What's the problem?Was thinking of a LEO prop depot for the refueling. So if you dual launch, you minimized the time needed to complete the mission. You way is also workable.
They can take a month or two to launch and refuel both in LEO, just the way they would assemble a Mars fleet to launch into a launch window. What's the problem?
Since you will need the tankers in whatever form for the Methane & Lox propellants for Mars missions anyway. Using them even inefficiently might be a better trade than developing a separate SEP inspace vehicle with a different propellant (Xenon) that is not readily available in large quantities.IMO the MCT tanker will not be too different from the MCT. Otherwise you will be developing yet another vehicle that can be reuse. Presuming you version of the MCT tanker is not expendable.It is cheaper to developed a single general purpose vehicle than 3 different specialized vehicles in parallel.
Quote from: Zed_Noir on 12/03/2015 10:38 am[snip]IMO the MCT tanker will not be too different from the MCT. Otherwise you will be developing yet another vehicle that can be reuse. Presuming you version of the MCT tanker is not expendable.It is cheaper to developed a single general purpose vehicle than 3 different specialized vehicles in parallel.Tankers are needed but they are hardly a 3rd vehicle, they are just stretched 2nd stages with a nose cone covering a Xenon/Krypton tank and a hose port. This can launch and deliver 100 mt of propellants of varying combinations, either all Metho-Lox from residuals or SEP propellants.
[snip]IMO the MCT tanker will not be too different from the MCT. Otherwise you will be developing yet another vehicle that can be reuse. Presuming you version of the MCT tanker is not expendable.It is cheaper to developed a single general purpose vehicle than 3 different specialized vehicles in parallel.
The SEP tugs would have an integrated Xenon/Krypton tank for it's own use or around 50 mt and a Metho-Lox tank for offloading to the MCT, around 150 mt would be sufficient. These tanks should mass 5 and 2.5 mt respectively and the rest of the vehicle would only come out to around 10 mt meaning it can be launched mostly fueled on the BFR.A vehicle this size is going to be a lot simpler to design and produce then the MCT itself which goes through incredible stresses and flight regimes. The SEP is basically made of off the shelf satellite parts, Solar panels and Hall thrusters both of which are going to be mass produced by SpaceX in it's Satellite Swarm.
Two tankers refuel 1 SEP with MethoLox and Xenon to make a delivery of Metho-Lox to EML1. One tanker refuels two SEPs with just Xenon to move two MCT's to EML1. That's 3 fuel launches and 2 MCT so a 2:5 ratio for cargo delivery. Nearly doubling the LEO to Mars efficiency at the cost of a small SEP tug that should be a fraction of the cost of the vehicles that are already necessary.
A single-stage BFR is not likely to be a good cargo or liquid ferry to LEO, much less to GTO. Payload mass fractions on a single stage are very small. You can expect a *reusable* single stage rocket-based launch vehicle to be extraordinarily difficult to do with any payload at only 360-380s Isp.
essentially a reusable second stage with a long-loiter package and refueling capability
Are you on L2, Burninate?