This question came up on a different thread, so I thought I would start a specific one to collect everyones thoughts.The subject came up when I responded to a statement from Robotbeat:Quote from: Coastal Ron on 10/05/2014 06:46 pmQuote from: Robotbeat on 10/05/2014 03:04 pmI will say one thing: since both designs chosen were capsules, they are both relevant for any future BLEO missions and should be considered for inclusion by mission planners.None of these vehicles will be evolved for BLEO - they are too small. Be glad to talk on another thread about it if you want...A number of people agreed with Robotbeat, or at least with the idea that Commercial Crew vehicles could be adapted for beyond LEO needs.My reasons for saying that Commercial Crew vehicles are too small is that I think we have learned that for humans to stay healthy in space that they need a lot of room, so future human space travelers are not going to be spending most of their time in a capsule like the Dragon or CST-100. Plus, capsules are really only designed for transporting humans to/from a planet with an atmosphere, so at most my view is that if we take them BEO it's only for use as a lifeboat and for the "last mile" of getting humans down onto a planet. And currently the only planet we know we can land them as currently designed is Earth, so why not leave them orbiting in LEO and just plan to meet back up with them in Earth orbit on the way back?If you think Commercial Crew vehicles will be adaptable for BEO applications, please state what those applications are. For instance, would you envision using a CST-100 for visiting an asteroid or only for trips to the Moon?And if you don't think they are applicable, go ahead and state what your alternative would be.
Quote from: Robotbeat on 10/05/2014 03:04 pmI will say one thing: since both designs chosen were capsules, they are both relevant for any future BLEO missions and should be considered for inclusion by mission planners.None of these vehicles will be evolved for BLEO - they are too small. Be glad to talk on another thread about it if you want...
I will say one thing: since both designs chosen were capsules, they are both relevant for any future BLEO missions and should be considered for inclusion by mission planners.
Quote from: WindyCity on 10/10/2014 01:58 amForgive me if this has been already discussed.Could a BA330 be mated with a Dragon 2 for BEO missions? I don't know what additional ECLSS would have to be added, but from what I've read, the radiation and meteorite shielding of the hab would appear to be adequate for travel in deep space. Also, the BA330 has a propulsion system. Could the hab be stationed in LEO and then hooked up to the crew capsule and then boosted onto an interplanetary trajectory?That is basically what the BA-330 is designed for... and the propulsion system is a 'tug' that moves the entire bit beyond LEO... or beyond whatever location (EML-1/2 for instance). I've not actually heard mention or seen written text that showed docked vehicle like Dragon 2 being accelerated with the BA-330, so the stresses at docking mechanism may be be limiting.Great Article on the topic:http://www.nasaspaceflight.com/2014/02/affordable-habitats-more-buck-rogers-less-money-bigelow/
Forgive me if this has been already discussed.Could a BA330 be mated with a Dragon 2 for BEO missions? I don't know what additional ECLSS would have to be added, but from what I've read, the radiation and meteorite shielding of the hab would appear to be adequate for travel in deep space. Also, the BA330 has a propulsion system. Could the hab be stationed in LEO and then hooked up to the crew capsule and then boosted onto an interplanetary trajectory?
Family of Tugs:The documentation also portrays a family of tugs that could be used in conjunction with Bigelow habitats for use beyond Low Earth Orbit.The fleet consists of the Standard Transit Tug, the Solar Generator Tug, the Docking Node Transporter and the Spacecraft Capture Tug.These tugs could be used to push the various Bigelow Habitats – and other payloads – to specific destinations in LEO, L2, Cislunar space and beyond.The four tugs are designed to be grouped together in various combinations, depending on the mission requirements. Notably, they are sized for launch on SpaceX’s Falcon Heavy rocket.The tugs could be launched independently, prior to rendezvous with other elements in LEO to form a complete transport system. Each of these tugs share propulsion, docking and avionic systems.
The BA 330-DS:The documentation also offers NASA a deep space version of its habitat, the BA 330-DS, for use beyond Low Earth Orbit. The BA 330-DS could be used by NASA, for example, at a Lagrange point or in lunar orbit.The BA 330-DS would be very similar to its LEO version. The main difference would be related to radiation shielding.
>What additional shielding would it need. It already has a water jacket to protect against cosmic rays and solar radiation.
Could they be parked in LEO and refueled as needed?What additional shielding would it need. It already has a water jacket to protect against cosmic rays and solar radiation.
The average dose-equivalent rate observed through the investigation was about 10 times the average exposure on Earth.
It takes about 600 m/s to capture at L1, or to leave L1 for Earth, with a travel time of about 5 days each way. So any capsule will have to carry an additional 1200 m/s of delta-v over what it receives from the launch vehicle. At 320s Isp, that means about 50% extra mass in propellant.For L2 it takes about 350 m/s one-way with a ~9 day travel time. So that's an extra 700 m/s, which at 320s Isp means about 25% extra mass in propellant.That's a significant amount of extra mass needed if going to a Lagrangian point and back.
That's a significant amount of extra mass needed if going to a Lagrangian point and back.
Quote from: metaphor on 10/13/2014 05:47 pmThat's a significant amount of extra mass needed if going to a Lagrangian point and back.Orion is supposed to have ~1.6 km/s in delta-v, so I don't see any problem with that.
Given that NASA is using ESA to build the service module for Orion, I rather doubt they would be as bad as Orion esp. as they could do LEO runs as well as BEO trips.
Quote from: mmeijeri on 10/13/2014 07:14 pmQuote from: metaphor on 10/13/2014 05:47 pmThat's a significant amount of extra mass needed if going to a Lagrangian point and back.Orion is supposed to have ~1.6 km/s in delta-v, so I don't see any problem with that.Well yeah, that's why the service module is there. A commercial crew vehicle would need upgrades like that, that would make it heavier and costlier, in order to go BLEO. In the end it would probably end up somewhat similar to Orion.
SINCERELY doubt it could be as expensive as Orion. The capsule dry mass is far less for Dragon and cst100, just to name one thing.
It's like putting an airport at the top of a mountain. Plane lands on an uphill runway, and stops without needing brakes, then takes off downhill without needing engines to reach takeoff speed.
Quote from: MP99 on 10/14/2014 08:19 amIt's like putting an airport at the top of a mountain. Plane lands on an uphill runway, and stops without needing brakes, then takes off downhill without needing engines to reach takeoff speed.Hey, I know that airport. Never been there, but as a former backpacking/climbing fanatic, I've read about it a number of times:http://www.weather.com/travel/mount-everest-airport-will-terrify-you-photos-20130618Had several daredevil pilots in the family too. Flew in and out of some places almost that scary with my dad.
A 4.2 km/s TMI can either be done in one burn from LEO, or ~3.2 km/s TLI + ~1 km/s post-EML. No advantage here, but no disadvantage, either.
Quote from: MP99 on 10/14/2014 08:19 amA 4.2 km/s TMI can either be done in one burn from LEO, or ~3.2 km/s TLI + ~1 km/s post-EML. No advantage here, but no disadvantage, either. Your analysis is spot on, but I think truth is even better than you suggest. There are paths to EML which combine a chemical burn for LEO departure with electric propulsion to transfer onto the EML-bound trajectory. So looking at required IMLEO, utilizing the amazingly high isp of electric propulsion for a portion of the transfer to EML can be a meaningful win.
I believe this is less true for DRO, but haven't myself done the required math. In either case, rendezvous in the cis-lunar vicinity before departure for Mars has huge mission safety advantages, because abort modes are more accessible. (With classic TMI, you have to look at each moment of a long Earth departure burn and verify there's a safe abort in case of a propulsion failure. With TMI post-EML, the burn -- and thus the vulnerability -- is shorter.)This all leads to the conclusion that EML (or DRO) rendezvous will be the Mars mission mode that one day is actually selected. Commercial crew and cargo to that rendezvous point are in the cards ... sooner or later depending on the stubbornness of those who refuse to admit it.
So looking at required IMLEO, utilizing the amazingly high isp of electric propulsion for a portion of the transfer to EML can be a meaningful win.