Author Topic: NASA examines options and flight paths for SLS EM-2 mission  (Read 31173 times)

Offline Khadgars

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Re: NASA examines options and flight paths for SLS EM-2 mission
« Reply #60 on: 12/15/2016 10:13 pm »
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?

My understanding is that there are 16 RS-25 engines to use, which is enough for 4 SLS missions.  I believe there are enough casing (18) for the first 8 SLS missions with 2 casing for spares.  Knowing that, RS-25E production will have to begin at least 4 years before new 5 Segment casings do.

https://www.nasaspaceflight.com/2016/11/orbital-atk-srb-plans-competitiveness-em-1-beyond/
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Offline mike robel

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Re: NASA examines options and flight paths for SLS EM-2 mission
« Reply #61 on: 12/15/2016 10:39 pm »
Thanks for that, so RS-25s are the thing to watch for...I stand corrected.

Offline brickmack

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Re: NASA examines options and flight paths for SLS EM-2 mission
« Reply #62 on: 12/16/2016 12:24 am »
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.

Offline TomH

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Re: NASA examines options and flight paths for SLS EM-2 mission
« Reply #63 on: 12/16/2016 12:55 am »
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.

Thinking along that time line, assuming that ITS does eventually fly, that will certainly be the death knell of SLS and Orion. Favoritism aside, with no bashing, that's just reality.

Offline Robotbeat

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Re: NASA examines options and flight paths for SLS EM-2 mission
« Reply #64 on: 12/16/2016 01:29 am »
Same goes for New Armstrong and its lander thing. Yeah, 2027 is quite a long ways out... That's 3 presidential terms away.
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Re: NASA examines options and flight paths for SLS EM-2 mission
« Reply #65 on: 12/16/2016 04:21 am »
Can you guys tie that thought back into EM-2 flight path options? Should those assumptions about non-NASA capabilities and the potential demise of SLS/Orion play into the orbit selection decision?
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Online oldAtlas_Eguy

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Re: NASA examines options and flight paths for SLS EM-2 mission
« Reply #66 on: 12/16/2016 02:52 pm »
Because of the possible commercial competitors going through development and testing at the time of EM-2, SLS/Orion needs to prove out the full set of capabilities to show it is ready for any mission design that fits within the SLS/Orion systems capabilities box.

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.

If the mission duration capability is not tested then a latter flight will have to test it and have the flight path abort for shortened mission duration. Meaning the Orion is not ready for any mission but still requires more testing.

The end item is that hopefully the SLS or SLS/Orion by 2027 has conducted 3 operational flights. Some combination of the Europa missions and Orion missions.

Offline Khadgars

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Re: NASA examines options and flight paths for SLS EM-2 mission
« Reply #67 on: 12/16/2016 03:25 pm »
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.

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.
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Offline Robotbeat

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Re: NASA examines options and flight paths for SLS EM-2 mission
« Reply #68 on: 12/16/2016 04:50 pm »
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.

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.
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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Offline Khadgars

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Re: NASA examines options and flight paths for SLS EM-2 mission
« Reply #69 on: 12/16/2016 05:28 pm »
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.

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.

Not necessarily.

Quote
"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."

EM-1 - 2018
EM-2 - 2021
EM-3 - 2023
EM-4 - 2024
__________
EM-5 - 2025
EM-6 - 2026
EM-7 - 2027
EM-8 - 2028
EM-9 - 2029

I suspect we will see production of RS-25E much earlier than you are proposing as NASA is looking at for at least one mission per year.
« Last Edit: 12/16/2016 05:29 pm by Khadgars »
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Offline Robotbeat

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Re: NASA examines options and flight paths for SLS EM-2 mission
« Reply #70 on: 12/16/2016 06:06 pm »
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.
« Last Edit: 12/16/2016 06:07 pm by Robotbeat »
Chris  Whoever loves correction loves knowledge, but he who hates reproof is stupid.

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Offline Khadgars

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Re: NASA examines options and flight paths for SLS EM-2 mission
« Reply #71 on: 12/16/2016 06:27 pm »
Considering NASA's own safe cadence is one flight per year, I would disagree with that assessment.  We shall see.
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Offline okan170

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Re: NASA examines options and flight paths for SLS EM-2 mission
« Reply #72 on: 12/16/2016 06:39 pm »
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.

2023 was the date if ESA decided not to provide the EM-2 SM.

https://forum.nasaspaceflight.com/index.php?topic=41649.msg1614880#msg1614880

Offline RonM

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Re: NASA examines options and flight paths for SLS EM-2 mission
« Reply #73 on: 12/16/2016 06:40 pm »
NASA states they are planning for one flight per year starting with EM-2. That's what we should be discussing, but in a different thread. This thread is about EM-2 options.

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Re: NASA examines options and flight paths for SLS EM-2 mission
« Reply #74 on: 12/16/2016 09:14 pm »
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.

That's a good observation. A trajectory is better if it allows prompt Earth return with low delta-v, while still allowing a long duration nominal mission.

It wasn't one of the options discussed in the article but I'm curious if a "double figure 8" would rate highly on this metric? Loop around the Moon. Then loop around the Earth, loop around the Moon again, and then return to Earth for reentry.
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Offline Proponent

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Re: NASA examines options and flight paths for SLS EM-2 mission
« Reply #75 on: 12/17/2016 03:50 pm »
You could manage a second pass to the moon's orbit, but I don't see how to arrange to approach the moon on both passes while keeping the mission short enough.

Offline brickmack

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Re: NASA examines options and flight paths for SLS EM-2 mission
« Reply #76 on: 12/17/2016 07:26 pm »
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.

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

Online sdsds

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Re: NASA examines options and flight paths for SLS EM-2 mission
« Reply #77 on: 12/18/2016 07:56 am »
how to arrange to approach the moon on both passes

Hmm. In a non-rotating frame the outbound leg of a standard free return looks just like an elliptical Earth orbit until lunar approach. And the return leg looks like an elliptical Earth orbit too after lunar departure. But the line of apses of those two orbits aren't the same: while we were inside the lunar Hill Sphere doing our swing-by our whole orbital ellipse got twisted around.

So on an Earth swing-by <wild waving of hands> the same thing could happen. The line of apses of the approach and departure trajectories could get twisted such that we were once again going to approach the lunar Hill Sphere.

I suppose rather than wildly waving my hands I ought to ... actually do a simulation or something.
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Offline Khadgars

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Re: NASA examines options and flight paths for SLS EM-2 mission
« Reply #78 on: 12/18/2016 04:00 pm »
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.

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

Not necessarily true.  The contract is for production restart that runs through Sept 30th 2024 that also includes 6 engines

Quote
"“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)"

You are referring to the part in the document that states the 5th set wouldn't be needed until 2027, which imo was due to the uncertainly of the SLS manifest at the time the contract was awarded over a year ago.  That doesn't preclude delivery of RS-25E before 2027 nor does it not allow for additional units to be purchased to meet the needs of a now, more clear SLS manifest. 

To be clear, additional contract(s) for RS-25E will need to be secured to provide clarity and the required capability above what is on the books now. 

Might I suggest we bring this conversation into a new thread for EM-3 onward, as we've gone far OT.

« Last Edit: 12/18/2016 04:20 pm by Khadgars »
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