Quote from: MATTBLAK on 10/06/2014 10:54 amIn my opinion (for what it's worth) Orion should have been largely composite in structure, much like the ATK Liberty proposal which I also think might have been a 'mere' 4.5 meters in diameter and doubtlessly thousands of kilos lighter than Orion's large aluminium/lithium etc structures. They did build a composite version of Orion, to see what the issues were. It wasn't any lighter. Ironically, that composite version of Orion then BECAME Liberty. :-) Cheers, Martin
In my opinion (for what it's worth) Orion should have been largely composite in structure, much like the ATK Liberty proposal which I also think might have been a 'mere' 4.5 meters in diameter and doubtlessly thousands of kilos lighter than Orion's large aluminium/lithium etc structures.
So are people thinking that Commercial Crew capsule vehicles (i.e. CST-100 and Dragon V2) could be an interim solution for short duration exploration? For non-NASA missions, or if for some reason the Orion is not available?Or that they could be used more expansively than that?
Quote from: QuantumG on 10/06/2014 02:07 amIt believe it's passing through the radiation belts too many times that TomH may have been thinking about.That's true also, however a habitat returning from Mars would need dozens of passes through the very upper atmosphere on a very high apogee ellipse. It would have no TPS at all and could incur very little -ΔV on each pass. I am no expert in orbital mechanics, however I believe it would take much more than the 2 weeks max you believe it would. That means more mass for food, O2, etc., and you have astronauts watching the Earth go by over and over while they cannot land, likely enduring psychological stress from being so near physically, while still so far away temporally.
It believe it's passing through the radiation belts too many times that TomH may have been thinking about.
IMHO, NASA should be building landers, either for Moon, Mars, or both (preferably Moon) which could double as craft to visit asteroids or Phobos/Deimos. Maybe also a deep space gateway in cislunar space or near Mars, perhaps also Mars habitats and infrastructure, maybe a SEP-based transit vehicle. Launch vehicles and now capsules are totally doable by commercial entities. It's a much better use of restores for NASA to be building landers and such, just buying the services for launch or even now crew taxis and logistics from the likes of Boeing, SpaceX, ULA, Orbital/ATK, Sierra Nevada, and Blue Origin.
That does reduce deep space mission mass. It also means, however, that upon return to Earth, the hab must be decelerated to orbital V prior to rendezvous with a taxi, which means taking the prop with you to deep space and back, or you rendezvous with a tanker prior to Earth arrival. The other choice is a taxi must rendezvous with the hab as it approaches Earth, and you lose the hab.
2. LEO to the region of the Moon and back - this would be a reusable vehicle, likely refueling and refurbishing in LEO. Getting to the Moon is pretty straight forward, but returning to LEO requires perfecting new techniques. But if we can't figure this part out then we're not going to be able to afford to send many people BEO.
If you think Commercial Crew vehicles will be adaptable for BEO applications, please state what those applications are.
It says Dragon v2 dry is about 4,200 kg.
Quote from: ngilmore on 10/06/2014 04:24 pmIt says Dragon v2 dry is about 4,200 kg. I'm pretty sure that's just an unsourced copy-paste from the Dragon v1 mass - it should be significantly higher than that with Superdracos/extra tanks, ECLSS, windows &c. Probably more like 6+ tons dry.
Need to add LAS mass
Quote from: AncientU on 10/06/2014 04:38 pmNeed to add LAS massYes, thank you, even more margin. NASA says the gross liftoff weight of the LAS is 7,314 kg.http://www.nasa.gov/pdf/617408main_fs_2011-12-058-jsc_orion_quickfacts.pdfThe same NASA fact sheet says the total Orion system gross liftoff weight is 31,380 kg.So that should be top line comparison when asking if commercial crew vehicles could be adapted for BEO.
2. LEO to the region of the Moon and back - this would be a reusable vehicle, likely refueling and refurbishing in LEO. Getting to the Moon is pretty straight forward, but returning to LEO requires perfecting new techniques. But if we can't figure this part out then we're not going to be able to afford to send many people BEO.Anyways, that's part of the reason why I don't think today's Commercial Crew capsules are part of the evolutionary line of vehicles that we'll need in the future - I just don't see how they help us scale up the number of people leaving LEO. And isn't that really the goal?
In terms of going to and from the region of the moon direct reentry to earth would probably be the best bet. It costs less in delta V and you get your vehicle back on the ground where it can be inspected and reused(in theory).
To me that's like saying all Boeing aircraft would have to land in Everett WA to be inspected and refueled after every flight. It's hard to scale a transportation system like that.
We have to get past the Apollo paradigm if we want to do more in space.