{snip}I should probably make it clear that I am not arguing against the use of L1/2 stations in the future. Once Lunar sourced propellant is available in sufficient quantity, they make perfect sense. I'm not trying to plan an inner solar system transportation network using existing Lunar propellant production capacity though. What I am trying to understand is how DSG actually helps locating, then building, Lunar production capacity. It would seem to me that it is hard to compete with LLO when SEP can replace ~25% of cargo lander chemical Dv using LLO.
Quote from: Joseph Peterson on 02/18/2018 07:17 pmQuote from: A_M_Swallow on 02/18/2018 10:21 amThe DSG's Power and Propulsion Element (PPE) is a solar powered space tug. A second one can be used to push consumables like food, water and power from LEO to a spacestation orbiting the Moon. Heavy items like habitat building and lunar rovers can also be transferred.Since payload, propellent and lander can arrive separately heavier items can be landed on the Moon from a spacestation than in a single launch.The ideal orbit for the DSG during construction of a Moon Base is probably very different from the orbit of the ship yard for the Mars Transfer Vehicle. Fortunately the DSG's orbit can be changed or a second one built.People could go on direct SLS/Orion flights to the DSG. Most cargo could be launched to LEO on commercial launch vehicles.So your saying we should operate two stations then?{snip}More like 3 spacestations.LEO gateway spacestation to load SEP and chemical tugs.LLO spacestation to garage lunar lander.EML-1/2 spacestation for loading and repair of Mars transfer vehicles.I think the manned Mars trip is 20-30 years away.
Quote from: A_M_Swallow on 02/18/2018 10:21 amThe DSG's Power and Propulsion Element (PPE) is a solar powered space tug. A second one can be used to push consumables like food, water and power from LEO to a spacestation orbiting the Moon. Heavy items like habitat building and lunar rovers can also be transferred.Since payload, propellent and lander can arrive separately heavier items can be landed on the Moon from a spacestation than in a single launch.The ideal orbit for the DSG during construction of a Moon Base is probably very different from the orbit of the ship yard for the Mars Transfer Vehicle. Fortunately the DSG's orbit can be changed or a second one built.People could go on direct SLS/Orion flights to the DSG. Most cargo could be launched to LEO on commercial launch vehicles.So your saying we should operate two stations then?{snip}
The DSG's Power and Propulsion Element (PPE) is a solar powered space tug. A second one can be used to push consumables like food, water and power from LEO to a spacestation orbiting the Moon. Heavy items like habitat building and lunar rovers can also be transferred.Since payload, propellent and lander can arrive separately heavier items can be landed on the Moon from a spacestation than in a single launch.The ideal orbit for the DSG during construction of a Moon Base is probably very different from the orbit of the ship yard for the Mars Transfer Vehicle. Fortunately the DSG's orbit can be changed or a second one built.People could go on direct SLS/Orion flights to the DSG. Most cargo could be launched to LEO on commercial launch vehicles.
I suspect that the DSG, or replacement e.g. Bigelow/ULA depot, will end up in LLO.For the Moon base a Bigelow B330-MDS module would mass 20-30 tonnes. That is payload to the transportation system since the mass of the lander and propellant are additional to that.https://en.wikipedia.org/wiki/B330
Quote from: ncb1397 on 02/18/2018 08:01 pmQuote from: Joseph Peterson on 02/18/2018 07:17 pmWhile this is an interesting thought exercise, I don't see how it gets us closer to the specifications a Lunar lander designed to work with SLS/Orion requires.The solution is an upgraded Orion service module made in the United States. Bump the solar power capability to 20 kw from 11 kw to match NeMO, add Next-C or AEPS engines. Acting as a lunar lander, It could self ferry itself ahead of crew to whatever orbit Orion can reach(might even be considered LLO) with the upgraded service module utilizing the extra lift capability of the Block 1B. The descent modules get re-used on the surface for power, consumable storage, fuel storage. Once you get some sort of fuel production going on the surface, you could look at fueling them and sending them back up to orbit. Orion would just use ESMs until this is available, freeing up Europe to focus on other stuff (like a European lunar hab equivalent to their contribution to ISS).Either that or base the lander at DSG like what seems to be the plan. The difference between 4.5 km/s and 5.5 km/s for a lander isn't exactly a deal breaker.That isn't the current plan though. NASA's RFI requested drop-in replacements for Shuttle OMS engines. I guess the SM tanks could be stretched but that will cut into payload capacity. How long would it take and how much would it cost before an upgraded Orion would be available? How many more SLS launches are needed to send cargo?https://www.nasaspaceflight.com/2018/02/nasa-releases-rfi-new-orion-service-module-engine/Why are you adding a ~20% margin for LLO to surface and back compared to a minimum margin of ~9% for L2 halo orbits?
Quote from: Joseph Peterson on 02/18/2018 07:17 pmWhile this is an interesting thought exercise, I don't see how it gets us closer to the specifications a Lunar lander designed to work with SLS/Orion requires.The solution is an upgraded Orion service module made in the United States. Bump the solar power capability to 20 kw from 11 kw to match NeMO, add Next-C or AEPS engines. Acting as a lunar lander, It could self ferry itself ahead of crew to whatever orbit Orion can reach(might even be considered LLO) with the upgraded service module utilizing the extra lift capability of the Block 1B. The descent modules get re-used on the surface for power, consumable storage, fuel storage. Once you get some sort of fuel production going on the surface, you could look at fueling them and sending them back up to orbit. Orion would just use ESMs until this is available, freeing up Europe to focus on other stuff (like a European lunar hab equivalent to their contribution to ISS).Either that or base the lander at DSG like what seems to be the plan. The difference between 4.5 km/s and 5.5 km/s for a lander isn't exactly a deal breaker.
While this is an interesting thought exercise, I don't see how it gets us closer to the specifications a Lunar lander designed to work with SLS/Orion requires.
If Congress actually cared about humans on Mars, they'd shovel a couple billion per year in SpaceX's direction and get out of the way.
Quote from: Joseph Peterson on 02/19/2018 12:30 am If Congress actually cared about humans on Mars, they'd shovel a couple billion per year in SpaceX's direction and get out of the way.That is not how it works. the congress never directly funds a company.
More like 3 spacestations.LEO gateway spacestation to load SEP and chemical tugs.LLO spacestation to garage lunar lander.EML-1/2 spacestation for loading and repair of Mars transfer vehicles.I think the manned Mars trip is 20-30 years away.
LLO does not seem necessary nor offer any significant advantage.
Quote from: Jim on 02/26/2018 12:24 pmQuote from: Joseph Peterson on 02/19/2018 12:30 am If Congress actually cared about humans on Mars, they'd shovel a couple billion per year in SpaceX's direction and get out of the way.That is not how it works. the congress never directly funds a company.Except of course that it (bizarrely to a European) mandates specific rockets for specific missions, thereby ensuring the manufacturers of those rockets get funded.
Quote from: IRobot on 02/26/2018 02:26 pmLLO does not seem necessary nor offer any significant advantage.It can, if you use it to avoid having to take your TEI fuel (and possibly rocket engine) down to the moon and back.
Wouldn't ELM-1 or 2 be a better location for a station and design a lander to be refueled there? Most companies and countries can reach these locations with existing rockets.
Space activities will always be mass limited. Colonisation will also be very money limited. Astrobotic Technology are currently charging $1,200,000 per kilogram to land a payload on the Moon. Even if larger landers get the price down to $100,000/kg transporting ten tonnes of fuel would cost10,000 * $100,000 = $1,000,000,000Bigelow claims it will sell you a spacestation for that billion dollars (placement extra).
Err...If we're dragging other providers claims into it, SpaceX claims to be able to do it (eventually) for around $50/kg, not $100000/kg.https://forum.nasaspaceflight.com/index.php?topic=41682.msg1731818#msg1731818(Assuming numbers applicable to making passenger transport plausible, and detanking and retanking in LEO and LLO with another vehicle. )Even more near-term launchers (including SLS) can probably comfortably beat $100000/kg.
Quote from: speedevil on 02/26/2018 10:21 pmErr...If we're dragging other providers claims into it, SpaceX claims to be able to do it (eventually) for around $50/kg, not $100000/kg.https://forum.nasaspaceflight.com/index.php?topic=41682.msg1731818#msg1731818(Assuming numbers applicable to making passenger transport plausible, and detanking and retanking in LEO and LLO with another vehicle. )Even more near-term launchers (including SLS) can probably comfortably beat $100000/kg.These figures are to the Moon's surface not to LEO." around $50/kg"Which decade?
For a 20 tonne payload that is $1,562,000,000 / 20,000kg = $78,100/kg
Quote from: A_M_Swallow on 02/27/2018 10:09 amFor a 20 tonne payload that is $1,562,000,000 / 20,000kg = $78,100/kgNo, it is not.See this thread.In short, 100% reusability slashes costs a lot. If it works, which is a more appropriate topic in other threads.