To save time and prevent multi-posting, I'm going to post my responses here in one post.
Well, three prototypes for possible habs are in orbit right now.
We call them space stations.
Three prototypes? I know of only two: The ISS and Bigelow's Genesis-II. Unless China has already launched Tiangong-1, that is.
The ISS is really the wrong paradigm for a transit hab vehicle. I think that the Russian Salut-6-class (also used for Mir and ISS) is a good idea, as are the Transhab systems being developed by Bigelow. I understand that there are certain advantages to carbon composite hulls over metal hulls when dealing with high-energy radiation too.
What would my idea solution be? Probably something not dissimilar to the BA-330 Nautilus. Alternately something based on the ATV with a wider semi-rigid composite hab cylinder and maybe an EVA airlock too.
Just for the record, I know that Lockheed have been promoting an Orion/OrionLab combination with a 'cargo' Orion to act as a hab space for long-haul missions. I don't know how realistic that is.
But I don't see this NEO Asteroid visit being any less costly than return moon landing.
This asteroid lander/long term hab module isn't going to be less costly than Altair.
Well... Maybe and maybe not. That I leave in the hands of those who know more about the subject than I.
FWIW, though, a Flexible Path hab/lab module wouldn't necessarily need a propulsion system of its own or the landing hardware and avionics. There may be some savings from that. Remember also that the hab module could possibly be utilised for many different missions including lunar orbiter, EML lab and even flyby missions for the inner planets. However, it is worth remembering that there will be mission equipment such as sensors for the encounter and surface experiment packages.
Remember that an asteroid 'lander' is something of a misomner. The Orion's RCS system will be able to handle the ascent on many NEOs, which have only theoretical levels of gravity. If anything, the engineering would be more like that of an orbit-to-orbit cargo tug which needs to dock with a large object that does not have a docking interface.
It
could end up cheaper.
Hard to get excited about the remote possibility of such a mission 15 years down the line. Way too long from now - we need to do more sooner.
Absolutely. The objective should be to have the first missions as soon after ISS retirement as possible. 2020 at the earliest, IMHO, with the first Orion free-return lunar fly-arounds (to test Orion's systems in the BEO environment) to happen as soon as their is an LV capable of performing TOI (maybe as early as 2016-18).
The longer the program takes to show results, the more likely a funding cut due to loss of interest becomes. The only way around this is to start doing scientifically-dubiouis but press-worthy 'milestone' missions as soon as possible. The obvious first ones would be the first Orion lunar free-return fly-around, followed by an Apollo-8-style lunar orbiter, possibly including an EML-to-LLO transfer.
I am personally a fan of the idea of a 'Moonlab' at EML-1. This allow NASA (and its international partners) to develop experience in BEO flight (and life-support technologies) without getting too far from Earth if there are problems. It also gives a fairly easy-to-reach destination for multiple flights for those years when there are no departure windows to more distant destinations available.
I'm sure that mmjieri will thank me for mentioning this: An EML-1 lab would also be in range of commercial crew and cargo vehicles launched by F-9H- or EELV-class LVs.
Opposition class, chemical propulsion based Mars missions (flyby or short orbital) require about 450 days. 6 months = 180 days.
Correct.
On the other hand a conjunction-class chemical mission is 180 days (6 months) outbound, eighteen months on the surface and 180 days back. That's a total of 900 day mission duration with an enormous amount of science possible on the Martian surface, whilst the opposition-class allows you just 30 days in LMO and even less on the surface; literally not worth the investment in the transfer vehicle (IMHO, anyway). Conjunction-class also offers a shorter free-return abort orbit (2 years)
and does't require the technically-challenging Venus flyby.
No reason for the Hab to be as expensive as Altair with its massive propulsion system. I do wonder however how Orion is going to move about since it depended on Altair for lunar orbit insertion. Anybody having some knowledge as to how they are planning to deal with that?
The simplest way to handle this would be to retain the EDS for as long as possible and use it for the orbit matching burns (it would be somewhat exaggerated to call it an 'orbital insertion' burn). I know that NASA has been thinking of using a Node/Centaur combo for the GEO construction mission. Maybe a version of Centaur, or maybe the ACES-41 four-engine Centaur evolution, could be used as a deep space propulsion module.