EDIT: Apologies, this belongs in Exploration Alternatives. I've posted it there but can delete this message here.====================================Following a lot of discussion about Phobos, a potential exploration scenario might include:1. Robotic precursor missions, including sample return (Phobos Grunt), and testing of technologies.2. Short stay mission departing from LEO: 30 to 60 days for a crew of 4-6 on the surface of Phobos.3. Long stay mission departing from HEO: Establish permanent base on Phobos using large scale inflatables (http://forum.nasaspaceflight.com/index.php?topic=18759.0) This focuses on part 2.The mission is assembled in Low Earth Orbit. The crew stay in a Bigelow BA 330 module for 6-9 months out, 30-60 day stay, and 6-9 months return. Water is recycled in the service module.The mission is launched using cryogenics. If available, a Jupiter Upper Stage with 175 tons of fuel will launch the stack to a Mars Transfer Orbit. Before Mars arrival, dehydrated waste is jettisoned. The mission uses aerocapture around Mars, and then a quick burn to meet with Phobos. The mission settle as Phobos, where crew spend 30-60 days doing a number of tasks: Drilling in to Phobos and testing methods of regolith processing; Testing water extraction and electrolysis equipment Testing a storm shelter inflating a 5m balloon under the regolith Testing anchoring methods Making observations of Mars possible remote piloting surface vehiclesAt the end of the stay, the crew leave behind the Phobos exploration module and return to Earth Transit (using storable propellants). The mission uses aerocapture around Earth to enter a highly elliptical orbit and then a high orbit. An Orion Capsule meets with the BA-330 to return the crew. The BA-330 and service module remains in orbit. Total mass in LEO is just under 300 tons, of which 175 tons is cryogenic fuel. The storable fuel is 53 tons, and the payload 72 tons. So four Jupiter 232 launches or about 12 EELV launches, plus an Orion crew module (and another one to collect or can it stay in orbit for 18 months.Key components are:Components Mass NotesBA-330 module 23 tons Source: WikipediaService Module 10 tons Incl solar panels, life support, water recyclingReturn supplies 4 tons Heat shield 3 tons Return rocket 5 tons Phobos scientific module 10 tons Outbound supplies 5 tons LEO transfer rocket 12 tons Based on Jupiter Upper StageMass and Delta-V estimates are attached.Is this doable for the mass? Any new developments needed that are not in development?It fits nicely with the Jupiter 246, given a 175 ton fuel capacity in the upper stage. But it would also work with the ULA EELV approach. There's no need for an Altair lander, but some novel ideas will be needed for testing. Thoughts?
Using Bigelow's large LEO hab module (that exists on paper only right now) also doesn't make any sense. You design your module to be as weighing as little as possilble. A BA330 is overkill in volume and doesn't provide the capabilities required for a Phobos mission, much less efficient GCR shielding. You also need to take your Orion with you, you need it for reentry on your way back.
Even with water recycling as currently done on the ISS, you have a 15-20kg per person requirement per day for supplies.For a 4-crew to Phobos mission and an opposition class 500 mission, that adds up to at least 30mt. You calculate for 9mt.Using Bigelow's large LEO hab module (that exists on paper only right now) also doesn't make any sense. You design your module to be as weighing as little as possilble. A BA330 is overkill in volume and doesn't provide the capabilities required for a Phobos mission, much less efficient GCR shielding. You also need to take your Orion with you, you need it for reentry on your way back.For a reasonable Phobos mass budget for a opposition class 440 day mission to Phobos using chemical propulsion, look here http://www.astronautix.com/craft/phoion88.htm
Too big a volume does not matter, we are not in an atmosphere. The extra mass has an effect but fortunately it is mostly air at low density.
One of the advantages of returning to L1 or L2 is that the returning Transfer Vehicle can rendezvous with a waiting Earth lander (capsule). The Orion never needs to leave Earth orbit. That saves a significant amount of propellant.
The required thickness of GCR shielding does need determining. Possibly by performing animal experiments at an L2 spacestation.
1. I thought a Bigelow might be overkill for 4 crew, but it's the only one on the drawing board. I suppose a simple polyethylene space capsule would be lighter.
2. Orion doesn't need to leave Earth Orbit. Return rendez-vous is in HEEO.
3. 15-20kg seems very high.
solution: reduce your crew to two, just like zubrin "athena"
1. The BA330 is not constructed to be a deep-space hab.2. Why would you want to carry a 23mt hab all the way to Mars, if you really only need to develop a 5-10mt hab for that purpose? You design your hab for the mission you need it for, you don't use overly large and heavy structures for that purpose. It will cost you enormously mass-wise if you do so without gaining anything from it.
QuoteOne of the advantages of returning to L1 or L2 is that the returning Transfer Vehicle can rendezvous with a waiting Earth lander (capsule). The Orion never needs to leave Earth orbit. That saves a significant amount of propellant.True, but there is a delta-v penalty for you to go to EML-1/2 then to Mars orbit and then back to EML-1/2, instead of doing the TMI burn from LEO and do a direct descent with Orion on your way back. The L1 and L2 approach is more complicated and also requires more mass lifted in total. It might be the way forward at some point in the future, but for a single Phobos mission, it doesn't make sense.
QuoteThe required thickness of GCR shielding does need determining. Possibly by performing animal experiments at an L2 spacestation.No, we have a lot of data on GCR and there are countless papers on passive shielding for deep-space missions.
At solar minimum, any mission longer than about 150 days exceeds the maximum tolerable dose for astronauts if you go for minimum shielding (10g/cmē). That being said, a 500 day mission is only possible with GCR shielding of some kind, at least 30g/cmē - which of course can be provided by scientific equipment and polyethylene shielding. But the point is, the BA330 does not provide such shielding and also has an internal structure (mission equipment in the middle of the module instead of on the walls as in the ISS) that does not help. To sum up, the BA330 is a. too large for the purpose and thus too heavy for the purpose, b. designed for LEO and not for deep-space and c. not idle from a GCR shielding point of view. If Bigelow is successful with his inflatable habs in the next years, they might be one of the bidders for a deep-space transhabs. But a specific product from items they advertise right now should not be used for a Phobos mission.
Quote from: A_M_Swallow on 09/20/2009 08:43 amToo big a volume does not matter, we are not in an atmosphere. The extra mass has an effect but fortunately it is mostly air at low density.1. The BA330 is not constructed to be a deep-space hab.2. Why would you want to carry a 23mt hab all the way to Mars, if you really only need to develop a 5-10mt hab for that purpose? You design your hab for the mission you need it for, you don't use overly large and heavy structures for that purpose. It will cost you enormously mass-wise if you do so without gaining anything from it.QuoteOne of the advantages of returning to L1 or L2 is that the returning Transfer Vehicle can rendezvous with a waiting Earth lander (capsule). The Orion never needs to leave Earth orbit. That saves a significant amount of propellant.True, but there is a delta-v penalty for you to go to EML-1/2 then to Mars orbit and then back to EML-1/2, instead of doing the TMI burn from LEO and do a direct descent with Orion on your way back. The L1 and L2 approach is more complicated and also requires more mass lifted in total. It might be the way forward at some point in the future, but for a single Phobos mission, it doesn't make sense.QuoteThe required thickness of GCR shielding does need determining. Possibly by performing animal experiments at an L2 spacestation.No, we have a lot of data on GCR and there are countless papers on passive shielding for deep-space missions.At solar minimum, any mission longer than about 150 days exceeds the maximum tolerable dose for astronauts if you go for minimum shielding (10g/cm²). That being said, a 500 day mission is only possible with GCR shielding of some kind, at least 30g/cm² - which of course can be provided by scientific equipment and polyethylene shielding. But the point is, the BA330 does not provide such shielding and also has an internal structure (mission equipment in the middle of the module instead of on the walls as in the ISS) that does not help. To sum up, the BA330 is a. too large for the purpose and thus too heavy for the purpose, b. designed for LEO and not for deep-space and c. not idle from a GCR shielding point of view. If Bigelow is successful with his inflatable habs in the next years, they might be one of the bidders for a deep-space transhabs. But a specific product from items they advertise right now should not be used for a Phobos mission.
Modifying an existing hab such as Sundancer or a BA 330 would be a lot cheaper then anything you'll save on TMI propellant.This is exactly what they planed back in the 60s by reusing skylab as habitation module.Sometimes the lightest mission is not going to be the cheapest.Payloads esp anything one off usually costs far more then the LV.A 23T launch is only going to cost 90M to 180M double that if you want to send it to Mars.R&D for a custom hab would be what a billion USD?
It's best to go ahead and deal with the extra mass so you get a more reliable vehicle and keep cabin fever at bay.
Besides I would not put a crew of four in anything smaller then 150 cubic meters for a mission of that duration.
It should be noted the Orion will not need a full service module since it's not performing any TEI burns.
Though presently Dragon is the only vehicle with a storage life long enough for a Phobos mission barring use of advanced propulsion.
Orion has a storage life of zero. It exists on paper only. Until there a successful test flight, it can't be used for planning purposes.The fact is that Dragon is closer than Orion is to a test flight. Success isn't guaranteed for either capsule.