Quote from: RonM on 07/02/2015 06:10 pmNASA's Mars DRA 5.0 from 2009 had eight launches, seven Ares V and one Ares I.Boeing's "Mission to Mars in Six (not so easy) Pieces" study presented in 2014 has five SLS launches. It uses an EML-2 gateway station.So six SLS launches isn't bad, especially since it doesn't require a gateway station.Mars Direct and Semi-Direct are too minimalist.Yes this is a "simple, cheap" Mars mission by NASA standards.
NASA's Mars DRA 5.0 from 2009 had eight launches, seven Ares V and one Ares I.Boeing's "Mission to Mars in Six (not so easy) Pieces" study presented in 2014 has five SLS launches. It uses an EML-2 gateway station.So six SLS launches isn't bad, especially since it doesn't require a gateway station.Mars Direct and Semi-Direct are too minimalist.
Absolutely, by government standards. Now we'll have to wait and see if the private sector and reusable rockets can lower the cost, but you have to plan on what you got. Right now, that's SLS.
Absolutely, by government standards.
The authors gave a presentation on their proposal a month before publication. The slides (attached) include some additional info and visualizations.
Orbital Mission1) Drop the Phobos base2) Leave Orion in Earth orbit-Reduces flights to 3 SLSs and frees up mass for fuel and supplies instead of dragging out extra vehicles-Lander Mission1) Directly send the DAV to Mars via single SLS2) Leave Orion in Earth orbit3) Minimize number of rendezvouses in Mars orbit involving DAV-Reduces flights at least to 5, possibly 4 SLSs
If we're nominally assuming 2, that means at least 3 years needs to be devoted to building just the rockets for a full-fledged landing party that's an extremely short one-shot deal; I know the government can be wasteful but this seems a lil much.
Overall not obvious improvements to me.
Quote from: RonM on 07/02/2015 10:00 pmAbsolutely, by government standards. Ok then, how would you make it simpler? The landers are about as simple as it gets, the ascent vehicle as well. Those are probably the biggest cost factors, so it makes sense to minimize their complexity. You need to push those landers from HEO to Mars, so you take an EUS because that's availabe. Even without SLS, you need some kind of big stage to do this, and a lot bigger one from LEO (or SEP, but you need a lot more power than 100kw for that).Then there's the habitat, NASA has plenty of experience with that and I'm sure they know what is needed here. They decide to resupply the habitat in HMO, in order to minimize the habitat's mass at departure from HEO and HMO. That helps keeping the MOI and TEI stages small. A 100kw SEP can pre deploy the TEI to HMO in a reasonable time frame, when launched with an SLS towards Mars.One could debate whether it would make sense to go back to cis-lunar space and not take Orion with them, but I guess that's a close call.For an expendable architecture with SLS available, I don't see it getting any simpler (short of Mars direct nonsense).
Yes, for an expendable architecture with SLS, it really can't get simpler than this. But I think you missed my point about the private sector, especially since you removed it from my quote. I was trying to avoid turning this thread into another "the company that shall not be named" thread. You know, NASA isn't the only group designing a Mars architecture.
Also, remember that SLS was mandated by Congress, not suggested by NASA. While this is a great architecture for using SLS, we might have something better if NASA got to spend five years doing research before designing an HLV. That was President Obama's plan. But, we got SLS instead, so we might as well try to figure out what to do with it.
Also, remember that SLS was mandated by Congress, not suggested by NASA.
While this is a great architecture for using SLS, we might have something better if NASA got to spend five years doing research before designing an HLV. That was President Obama's plan. But, we got SLS instead,
so we might as well try to figure out what to do with it.
Quote from: RonM on 07/03/2015 04:55 pmQuoteso we might as well try to figure out what to do with it.Exactly. Which is what this is. If you didn't work for NASA and weren't convinced more than 4 SLS's would ever be produced you would choose a different architecture. But they do work for NASA and SLS is the designated standard NASA launch vehicle.
Quoteso we might as well try to figure out what to do with it.Exactly. Which is what this is. If you didn't work for NASA and weren't convinced more than 4 SLS's would ever be produced you would choose a different architecture. But they do work for NASA and SLS is the designated standard NASA launch vehicle.
Orbital mission:- The Phobos habitat provides supplies for the crew, you'd have to add that to the transfer habitat, increasing its mass by maybe up to 10t (note the hab gets resupplied im HMO for the other missions). Also requires the hab to go down from HMO to Phobos orbit, increasing MOI and TEI stage mass. 100kw SEP would likely be too slow to do that for the crewed hab. Note commonality with the Mars landing missions is important.- Requires more delta-v to break the habitat into cis-lunar space. Also would require an additional transfer vehicle from HMO to Phobos orbit (if the hab doesn't go there). But yeah, might not be a bad idea.
Quote from: Oli on 07/03/2015 11:52 amOrbital mission:- The Phobos habitat provides supplies for the crew, you'd have to add that to the transfer habitat, increasing its mass by maybe up to 10t (note the hab gets resupplied im HMO for the other missions). Also requires the hab to go down from HMO to Phobos orbit, increasing MOI and TEI stage mass. 100kw SEP would likely be too slow to do that for the crewed hab. Note commonality with the Mars landing missions is important.- Requires more delta-v to break the habitat into cis-lunar space. Also would require an additional transfer vehicle from HMO to Phobos orbit (if the hab doesn't go there). But yeah, might not be a bad idea.As far as TEI and HMO-Phobos masses, those payloads are already being delivered by SEP-tugs. If you leave the weight of the Orion behind at Earth a 40 mt DSH with a 40 mt stage could break into HMO. Dragging the Orion's weight around is the main thing that would limit a hab's function. Capturing into and then maneuvering between HMO and Phobos orbit (with Deimos in between) is on the order of 3 km/s for a round trip. If the hab arrives with 40 tonnes of hypergolic fuel that's enough for MOI and rendezvousing with Deimos. The delivered stages could readily be used for Phobos operations and returning to Earth. Also, why are you complaining about the hab increasing TEI mass? The plan clearly shows the hab returning to Earth.The number for consumables has always varied with architectures; for Mars Direct it was 7 mt, for DRM 5.0 it was 13 mt. A hab's weight could easily include this with a budget totaling 40 mt; most plans for DSHs put their dry weight in the area of 25 mt. That gives 15 mt not devoted to hardware for crew needs.The lander half is going to be the hard part. The orbital half could reasonably be trimmed down while drawing on existing technology.
The number for consumables has always varied with architectures; for Mars Direct it was 7 mt, for DRM 5.0 it was 13 mt. A hab's weight could easily include this with a budget totaling 40 mt; most plans for DSHs put their dry weight in the area of 25 mt. That gives 15 mt not devoted to hardware for crew needs.
Overall I find the mixing of SEP and Chem in this architecture to be very poor, the SEP is underpowered as it reflects zero improvement on ARM which is ridiculously conservative. The Chem stages don't make use of oberth effects and are big and bulky.This proposal is almost Zubrin like in it's rejection of tech development, even the technologies already under development by NASA right now like HIAD. Did their sand charts assume NASA's tech development budget gets zeroed out and all the money dumped into their program?Lastly the presenters make the absurd claim that "by being specific with out plan our international partners can see themselves IN the plan and will come on board", which would makes sense if your specifics weren't composed of ALL AMERICAN VEHICLES.
- The SEP for ARM has 50kw, this one 100kw. SEP for ARM is expected to launch in 2020, and SEP for the Phobos mission in 2029. There is not a lot of time. Then there's the question of cost. An additional SLS might cost as little as $500m, if you stay within 2 launches per year (which this architecture does, more or less). A 100kw SEP is unlikely to be cheaper (a comsat can already cost as much), ARM costs $2.6bn, development included. I would like to see more powerful SEPs though, especially the hybrid approach which can return within 4 years is very interesting.
ARM costs $2.6bn
That's not to cost to manufacture the SEP, that's the combined cost of all development, an Orion and the SLS that launches it, and ground operations through the course of the mission. The SEP stage development is a pittance of that total and comes out of the NASA tech development budget.As for 9 years between ARM and their Phobos mission date, that is ages in the SEP world. That's the amount of time between Deep Space 1 and the Dawn Probe which was a huge leap forward in capabilities. It is absurd to think that our SEP would stagnate so much that 9 years after ARM we can't do any better then that. Even the ARM SEP developers say it can scale to 300 kw.