It's a little spooky to see Orion providing its own TLI. Isn't it a bit late in the Orion design effort to be considering this? The requirement would be 443.8 m/s of delta-v I think.
I don't like this since it puts the crew through the radiation belt many more times than necessary.
Also, testing Orion for one day is insufficient for a Lunar mission. Apollo 7 tested the CSM for nearly 11 days in LEO.
My preferred solution is to launch Orion uncrewed to the ISS on a Delta IV Heavy, where crew can transfer to it and perform a 10 day mission in LEO, properly testing all the systems. EM-2 should be a mission that only launches the CPL so that the new Block IB EUS can be tested without risk to the crew.
At this point, I almost consider EM (the propellantless drive) and EM (the SLS exploration missions) about equally likely.
Can someone explain NASA’s fascination with DRO?IMO it takes too much time and Delta V to get to from Earth.IMO it takes too much time and Delta V to get to the Moon from DRO.L1,L2, NRO and even High Lunar Orbits looks better IMO.
while superior and seemingly more "luxurious" than Apollo, such luxury apparently cost it the ability to directly enter low lunar orbit
Quote from: sdsds on 12/01/2016 08:09 pmIt's a little spooky to see Orion providing its own TLI. Isn't it a bit late in the Orion design effort to be considering this? The requirement would be 443.8 m/s of delta-v I think.Orion's delta-V is about 1500 m/s (or 4920 ft/s, as NASA prefers to put it), so it does seem feasible, with plenty of margin for mid-course corrections.
The figures I've seen before were about 600 m/s total for insertion and departure burns on a DRO mission with Orion
But then I had a numerical think about radiation doses during multiple passes through the van Allen Belts once before, in the context of multi-pass aerobraking. To make a long story short, if you have a look at the last attachment to this post, you'll see that the crew of Apollo 13, which made two passes through both van Allen Belts and, like the proposed EM-2 baseline mission, didn't spent a lot of time near the moon, got skin average doses of 2.4 mGy (1 rad = 0.01 Gy). Even if you assume that dose came entirely from the van Allen Belts, which, of course, it didn't, then scaling the Apollo 13 results to EM-2's six passes gives a total dose of 7.2 mGy. That's not a lot: the Apollo 14 crew, for example, got 11.4 mGy.
Following successes and agreements on the Ariane 6 programme, Airbus Defence and Space is particularly pleased by the ESA space ministers’ commitment to manned space activities, notably their green light for ESA to start working on a second European Service Module for the Orion exploration programme. This European contribution will provide the future US-manned capsules Orion with power and propulsion. Airbus is already prime contractor of the first European Service Module for NASA’s Orion spacecraft. The first un-crewed mission, Exploration Mission-1, will be launched in 2018, followed by the first crewed mission to be launched in 2021.
It is probably more accurate to say that in the Constellation architecture the task of lunar orbit insertion was assigned to the Altair lander's propulsion budget rather than the Orion SM propulsion budget. (That was because Altair would have had hydrolox or maybe methalox propellant efficiency.)
Although the notion for a mere lunar flyby feels like a cheap cop-out, I can respect one point of it: the loiter in high Earth orbit. Wasn't there a notion years ago that, during the early flights of Orion, that it was considered wise to check the vehicle out first in an Earth orbit before pushing all the way to the Moon? It feels like a reflection back to that, which is wise given the uncertainties there are for Orion, especially the ESM and the EUS.
If anything frustrates me aside from delays, I'd say it's the inability to decide what orbit or otherwise where in Cis-Lunar space. One year it's Lagrange points, another it's Distant Retrograde Orbit, and now this 'Near Rectilinear Orbit' stuff? Pick a damn orbit for crying out loud!
Quote from: redliox on 12/02/2016 11:58 pmAlthough the notion for a mere lunar flyby feels like a cheap cop-out, I can respect one point of it: the loiter in high Earth orbit. Wasn't there a notion years ago that, during the early flights of Orion, that it was considered wise to check the vehicle out first in an Earth orbit before pushing all the way to the Moon? It feels like a reflection back to that, which is wise given the uncertainties there are for Orion, especially the ESM and the EUS.Yes, and that still seems to be the plan.
Quote from: Proponent on 12/02/2016 07:08 amOrion's delta-V is about 1500 m/s (or 4920 ft/s, as NASA prefers to put it), so it does seem feasible, with plenty of margin for mid-course corrections.The figures I've seen before were about 600 m/s total for insertion and departure burns on a DRO mission with Orion, so even with an additional ~500 m/s for TLI there should be ample margins. Not sure how much that will impact comanifested payload capacity though
Orion's delta-V is about 1500 m/s (or 4920 ft/s, as NASA prefers to put it), so it does seem feasible, with plenty of margin for mid-course corrections.
Quote from: redliox on 12/02/2016 11:58 pmIf anything frustrates me aside from delays, I'd say it's the inability to decide what orbit or otherwise where in Cis-Lunar space. One year it's Lagrange points, another it's Distant Retrograde Orbit, and now this 'Near Rectilinear Orbit' stuff? Pick a damn orbit for crying out loud!I share your frustration. I think this situation is the natural consequence of politicians telling the engineers what hardware to build, and then compounding the problem by being unwilling to fork over adequate funding for the hardware they've insisted be built.
You are right: the high lunar orbits are all pretty much the same. The spacecraft is floating around vaguely in the vicinity of the Moon, without ever getting very close to it. A good way to think about them is that they are really just orbits around the Earth much like the orbit of the Moon around the Earth, except the presence of the Moon perturbs them somewhat.There's nothing "there" at any of them; they are all just variations on "nowhere." That makes it difficult to get very excited about any them, and I think the NASA public affairs people are aware of that problem.Sadly, one way they do vary that is easy to understand is that some of them would take astronauts further from Earth than any human has ever before traveled. Is that important in some scientific or engineer way? Well, no. But it might be something the kids can get excited about!
@jongoff: I just read your blog post, "Lunar Orbital Facility Location Options," at:http://selenianboondocks.com/2016/04/lunar-orbital-facility-location-options/It makes excellent reading in the context of this thread!I'm curious what your astrogator friends say about the cost (delta-v, delta-t) of moving between an NRO and an EML2 halo. (Or what anyone else's astrogator friends say about it!)If the NRO is (as one of the charts you show seems to indicate) essentially a lunar orbit with perilune of 2,000 km and apolune of 75,000 km the apolune velocity is something like 77 m/s. The circular orbital velocity at that distance is 253 m/s, So the cost to head off from there towards just about anywhere in cislunar space would max out at something like 77 + 253 = 330 m/s.And can't a careful insertion into an EML2 halo orbit be almost free, given enough time?
Quote from: sdsds on 12/06/2016 08:00 am@jongoff: I just read your blog post, "Lunar Orbital Facility Location Options," at:http://selenianboondocks.com/2016/04/lunar-orbital-facility-location-options/It makes excellent reading in the context of this thread!I'm curious what your astrogator friends say about the cost (delta-v, delta-t) of moving between an NRO and an EML2 halo. (Or what anyone else's astrogator friends say about it!)If the NRO is (as one of the charts you show seems to indicate) essentially a lunar orbit with perilune of 2,000 km and apolune of 75,000 km the apolune velocity is something like 77 m/s. The circular orbital velocity at that distance is 253 m/s, So the cost to head off from there towards just about anywhere in cislunar space would max out at something like 77 + 253 = 330 m/s.And can't a careful insertion into an EML2 halo orbit be almost free, given enough time?I'll ask. My guess is that you can move between NROs and EML2 for very low propellant costs, if you're willing to take a lot of time. Orbits like those often have Weak-Stability Boundary tricks you can play. No guarantees on a quick reply though. I'm in proposal/final report writing hell for the rest of the week.~Jon
I put up a thread to discuss orbits and the use around the Moon here:https://forum.nasaspaceflight.com/index.php?topic=41784.0[...] The real question is, afterwards, what orbits will Orions fly...and even furthermore what orbit a Deep Space Habitat/Lunar Space Station would occupy. The lower or more extreme the orbit, the less useful to Mars it becomes, so more solid decisions will need to be made on whether a habitat around the Moon serves the cause for Mars in the long-term.
As far as orbits, for EM-2 I am going to guess NASA is going to stay on the cautious side and downplay it as purely a test primarily in high Earth orbit with the simple lunar flyby partially for cheesecake.
[...] makes this clearly a "test out the new hardware" mission.[,,,]
I'll trust your judgement about what is an option for EM-2.
But note that for Apollo all TLI impulse was provided while in LEO reached from KSC. For EM-2 only the SLS portion of the TLI impulse must be provided in that kind of orbit.
And then there's yet another possibility. The Chinese have published (in the the AIAA Journal of Guidance, Control, and Dynamics) some research on what they call, "Multi Segment Lunar Free-Return Trajectories." In their scheme each trajectory segment is a free return. But they perform a maneuver days after TLI. (It's sort of like where some Apollo flights departed from free return.) I believe that approach might reduce the delta-t and perilune distance penalties.
It looks like Popular Mechanics is reporting the ideas laid out by the Advanced Concepts Office at Marshall as being the "plan of record." Not sure if that's true... but we can hope!Or is Popular Mechanics saying something different than what Smitherman said?https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20160012094.pdf
Quote from: sdsds on 12/10/2016 08:33 pmIt looks like Popular Mechanics is reporting the ideas laid out by the Advanced Concepts Office at Marshall as being the "plan of record." Not sure if that's true... but we can hope!Or is Popular Mechanics saying something different than what Smitherman said?https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20160012094.pdfLooking at the hab options considered they favor something sized like the SLS tankage at 8+ meter diameters.
Since 8 metres diameter is too wide for rail tunnels it will have to be brought in by barge. The workshop will have to be near a river or the sea shore.
Looking at the hab options considered they favor something sized like the SLS tankage at 8+ meter diameters.
I hope the large hab is openly competed. Would the RFP likely be timed before or after completion of EM-2? That is, would any lessons learned from EM-2 need to be carried forward into the hab requirements?
I'm disappointed in the timidity in decision making.Go for the Moon, get into orbit and show some marbles. It was possible in 1968, I would hope it's possible 50+ years later.
Quote from: wannamoonbase on 12/14/2016 06:55 pmI'm disappointed in the timidity in decision making.Go for the Moon, get into orbit and show some marbles. It was possible in 1968, I would hope it's possible 50+ years later.I don't think that's a fair thing to say. In 1968, a budget surge had NASA at 4.5% of the federal budget, and most of that was for the manned deep space program. Today NASA is getting about 0.5% of the federal budget and the manned deep space program is only a fraction of that. It's easy for us to sit back and criticize, but these guys have to be very careful with the limited amount of money they are given.
I'm disappointed in the timidity in decision making.-2 fGo for the Moon, get into orbit and show some marbles. It was possible in 1968, I would hope it's possible 50+ years later.
Basically, I'm just restating what redilox said about the budget being much less than Apollo's: with less money, less testing is possible.
Quote from: Proponent on 12/15/2016 01:09 pmBasically, I'm just restating what redilox said about the budget being much less than Apollo's: with less money, less testing is possible.Much appreciated As far as EM-2 itself is concerned, it still seems possible. If anything I just see the ESM as the weak point; both in schedule and for the fact it still limits Orion's performance. It could suffice for some activities, but not directly with lunar landings (as in descending as far as low lunar orbit where that magic happens). Just as the SLS is going to be upgraded, so should the SM for Orion, whether it be American or European-made. However I wouldn't expect an upgraded SM until at least EM-5+ due to the budget.
I think that is certainly possible. I also think is likely we'll see something similar to the 5 Seg boosters. Instead of a whole new design, we'll end up with upgraded versions of the current boosters. Both of which to happen towards end of 2020's.Everyone loves to rag on the EM missions, but there is not a single entity currently bending hardware that comes even close to this type of exploration outside of NASA. SpaceX may get into this game, but that is yet to be seen especially after the financial crunch they're experiencing from the recent failure.Gods Speed to both of them...
The telling time will come, unless I missed it, of ATK being told to start making the 1sts set of SRBs after the current casings are exhausted. Another indicator is the number of SSMEs they have available. Will they last longer than he casings?
Note that the new RS-25Es aren't expected to be built until 2027. 4 flights in 9 years, assuming no delays in production restart.
Quote from: brickmack on 12/16/2016 12:24 amNote that the new RS-25Es aren't expected to be built until 2027. 4 flights in 9 years, assuming no delays in production restart.I don't believe that this still holds true. The most recent EM mission schedule has at least 8 missions by 2029, which would necessitate an earlier production start to RS-25E.
Quote from: Khadgars on 12/16/2016 03:25 pmQuote from: brickmack on 12/16/2016 12:24 amNote that the new RS-25Es aren't expected to be built until 2027. 4 flights in 9 years, assuming no delays in production restart.I don't believe that this still holds true. The most recent EM mission schedule has at least 8 missions by 2029, which would necessitate an earlier production start to RS-25E.Realistically, the 4th would be 2025 at earliest and 2027 would be the fifth, which would necessitate RS25 production. But of course you'd need to start production several years earlier.
"After its maiden flight with a pilot in tow, NASA hopes to begin annual flights to the lunar orbit starting in 2023. All but one of the eight planned missions in NASA's latest flight manifest will be dedicated to the assembly of the mini-International Space Station in lunar orbit. Various pieces of the future habitat will be hitchhiking on each Orion flight."
I said realistically. I'd bet hard cash EM2 isn't launching until 2023 at earliest, then launches every two years after that is most realistic. Which means you can push off RS25 production for several more years.NASA "looking at" something and NASA realistically doing something are two different things.
The one capability that impacts on flight path design of EM-2 is mission duration for the Orion. The flight path needs to be able to be shortened if problems with the mission duration capabilities are found.
how to arrange to approach the moon on both passes
Quote from: Khadgars on 12/16/2016 03:25 pmQuote from: brickmack on 12/16/2016 12:24 amNote that the new RS-25Es aren't expected to be built until 2027. 4 flights in 9 years, assuming no delays in production restart.I don't believe that this still holds true. The most recent EM mission schedule has at least 8 missions by 2029, which would necessitate an earlier production start to RS-25E.This information comes from NASAs defense for sole-sourcing RS-25 from Aerojet. That was less than a year ago, and stated that not only would the 5th flight be in 2027, but that they didn't think Aerojet or any other company could deliver the engines faster because restarting the production line will take so long
"“In order to meet SLS Program flight manifest requirements, production of RS-25 flight engines will be concurrent with the engine recertification effort. The number of new flight engine: to be included as part of this action is six (6)"