Unless I'm misinterpreting, NASA's overview of Orion:https://www.nasa.gov/exploration/systems/orion/about/index.htmlseems to indicate that Orion is intended for flights to Mars, or at least the vicinity of Mars, as well as to the Moon. I'm no expert on Mars missions, but from what I've read, a Mars mission would require a one-way journey of at least six to eight months, depending on the relative positions of the Earth and Mars at the time of launch.Given Orion's Apollo-based design, I'm wondering how Orion will be able to carry sufficient oxygen, food, fuel etc. to support four (or even two) astronauts for such a period of time?
Looking at the Mars Base Camp mission design, as just one example, might help clarify the role Orion is imagined to play. https://www.lockheedmartin.com/content/dam/lockheed-martin/eo/photo/webt/Mars-Base-Camp-2028.pdfNote for example that for the return to Earth, the astronauts leaving the vicinity of Mars are put on a trajectory towards Earth that has them entering the atmosphere at 11.5 km/s. Orion would be taken along with the astronauts to Mars so they could use it to get safely home.
just take enough fuel to decelerate the living quarters into Earth orbit
Actually, all that’s REALLY needed to make Gateway into a Mars Transfer Vehicle, beyond the extra modules already planned, is a beefy chemical transfer stage using some sort of low boil-off or storable chemical propulsion.
Such a sad mission architecture.
Quote from: Robotbeat on 11/09/2020 04:56 pmActually, all that’s REALLY needed to make Gateway into a Mars Transfer Vehicle, beyond the extra modules already planned, is a beefy chemical transfer stage using some sort of low boil-off or storable chemical propulsion.They already are planning a beefy chemical propulsion module with the HLS. If they are able to aggregate the listed gateway components (Orion, Dragon XL, iHAB, PPE, HLS, HALO, ESPRIT) like they currently plan to, they could probably mount a mars orbital mission with a smaller crew with minimal modifications to some of the components. I'm waiting on more data on each of the HLS providers and the down-select to confirm this. But gateway wouldn't be useable in lunar orbit for a few years and isn't the most efficient vehicle for the job.
Yes, if they improve it a bit by qualifying it for longer duration and keep it attached to a much larger Mars Transfer Vehicle.Gateway is a lot like a Mars Transfer Vehicle except with a bit too small of a propulsion element. Double or quadruple the PPE, add another module or two for more space and supplies, and you’ll have a complete Mars Transfer Vehicle. (Probably need a chemical kick stage module to speed TMI and maybe capture at a high Mars orbit.)
Quote from: Hauerg on 11/09/2020 05:22 pmSuch a sad mission architecture.I basically agree with this assessment. The architecture is built around a subservience to the rocket equation, and the notion that propulsion gets prohibitively expensive the "further out" you use it. (In this case the returning Orion is so "far" from its launch site that it has essentially zero propulsion budget remaining and relies on atmospheric braking to slow down.)As many have opined, the solution to breaking the tyranny of the rocket equation is to produce propellant somewhere along the way. And the surface of Mars sure seems like a great place to do that!
Quote from: sdsds on 11/09/2020 05:40 pmQuote from: Hauerg on 11/09/2020 05:22 pmSuch a sad mission architecture.I basically agree with this assessment. The architecture is built around a subservience to the rocket equation, and the notion that propulsion gets prohibitively expensive the "further out" you use it. (In this case the returning Orion is so "far" from its launch site that it has essentially zero propulsion budget remaining and relies on atmospheric braking to slow down.)As many have opined, the solution to breaking the tyranny of the rocket equation is to produce propellant somewhere along the way. And the surface of Mars sure seems like a great place to do that!You misunderstand the MBC architecture in several ways.1. Water delivery is intended only for the first few years, and is actually one of the key distinctions it offers over other architectures. Coupled with a reusable single-stage lander, this allows a single expedition to visit multiple points on the surface over the span of a few months, not being tied to a single base. ISRU can come later (and is inherently compatible with a hydrolox lander and transfer vehicle), but would force each landing site to be semi-permanent, with a large industrial setup and months stay time at minimum. MBC allows that to be deferred until an ideal permanent site can be selected, and once this transition is made, nothing changes for the existing reusable hardware other than adding the ISRU plant. Even the Water Delivery Vehicles are meant to be repurposed as permanent depot modules once ISRU is established2. No, the returning Orion doesn't do a direct entry from a Mars-Earth interplanetary trajectory. The whole stack enters lunar orbit at the end of the mission, then Orion returns as normal. This allows most of the mission hardware to be reused. Carrying Orion along at all is... questionable, given you could just as well have Orion stay in lunar orbit to drop off and pick up the crew, but the idea is that it allows for more abort options (both on departure and return), and also allows Orion to be dual-use for visiting Phobos/Deimos
I imagine that the best 'parking spot' for the MTV would be one of the EML halo orbits. Hence Gateway - I think that NASA's forward planning for Mars is already assuming that they won't take an Orion all the way to Mars and back.
Quote from: Ben the Space Brit on 12/01/2020 08:48 amI imagine that the best 'parking spot' for the MTV would be one of the EML halo orbits. Hence Gateway - I think that NASA's forward planning for Mars is already assuming that they won't take an Orion all the way to Mars and back.Yes, most of the architectures I've seen lately use NRHO (that's because SLS can't really do payload to LEO and NASA assumes SLS - let's not rehash this argument please) and have Orion serve pretty much solely as a crew transfer vehicle.