Author Topic: NASA's Artemis Program Updates and Discussion Thread 3  (Read 708418 times)

Offline TheRadicalModerate

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Re: NASA's Artemis Program Updates and Discussion Thread 3
« Reply #40 on: 07/31/2019 09:05 pm »
Except I'm not sure your calculations are right because that "70t to LEO" number is old, old, old and has not been used in any SLS materials for the past 2 years. The modern figure is 95t to LEO.

95 t to LEO assumes the ICPS is depleted to reach 200 km circular LEO. I haven't seen any evidence that the Block 0 version can do 95 t without ICPS. It would be about 75 t but very sensitive to final burnout mass because the core stage is extremely large.

It's also pretty sensitive to gravity drag.  After SRB jettison, the core + 70 t payload still has a T/W of not quite 1.

Offline Mammutti

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Re: NASA's Artemis Program Updates and Discussion Thread 3
« Reply #41 on: 07/31/2019 09:19 pm »
https://twitter.com/BoeingSpace/status/1156655836514738177

Quote
Farther and faster: The next stage of America’s Moon rocket is taking shape to dramatically reduce travel time in space and carry more on a single flight. The Boeing-built @NASA_SLS Exploration Upper Stage will fly on Artemis-3.


Offline dglow

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Re: NASA's Artemis Program Updates and Discussion Thread 3
« Reply #42 on: 08/01/2019 12:04 am »
https://twitter.com/BoeingSpace/status/1156655836514738177

Quote
Farther and faster: The next stage of America’s Moon rocket is taking shape to dramatically reduce travel time in space and carry more on a single flight. The Boeing-built @NASA_SLS Exploration Upper Stage will fly on Artemis-3.

Wow, so Boeing got it back. Good job.

This means EUS will be man-rated for its first flight.

Online jongoff

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Re: NASA's Artemis Program Updates and Discussion Thread 3
« Reply #43 on: 08/01/2019 03:59 am »
The original approach was reusable.

Now with 2024 objective expendable is allowed for a Mark I version of the architecture, the sustainable, reusable version coming later.

With the usual risk to be stuck with the first one. How to justify to develop a new architecture when you have one which works?

As a European I could provide the example of Ariane 5 ECA which was supposed to be an interim solution waiting for the Vinci engine but I am sure there are many in the US.

As someone who worked in for several years in what was supposed to be a temporary Marine Corps building in Mojave that was built during WWII, I can tell you that there are few things more permanent than a temporary solution...

IOW, I totally agree with your concern. If we skip reusability for speed, it'll just make things easier to cancel down the road. Lander reusability doesn't have to be that hard either. There are several ways to get it from day one without requiring a lot of headache.

~Jon

Offline Steven Pietrobon

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Re: NASA's Artemis Program Updates and Discussion Thread 3
« Reply #44 on: 08/01/2019 07:59 am »
Except I'm not sure your calculations are right because that "70t to LEO" number is old, old, old and has not been used in any SLS materials for the past 2 years. The modern figure is 95t to LEO.

My simulations show 89.0 t payload to LEO. If you include the empty iCPS at 5.2 t, that gives an IMLEO of 94.2 t, close to your 95 t figure.

http://www.sworld.com.au/steven/space/sls/
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline jadebenn

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Re: NASA's Artemis Program Updates and Discussion Thread 3
« Reply #45 on: 08/01/2019 08:02 am »
My simulations show 89.0 t payload to LEO. If you include the empty iCPS at 5.2 t, that gives an IMLEO of 94.2 t, close to your 95 t figure.

http://www.sworld.com.au/steven/space/sls/
Well now I don't know who to believe.

To clarify, you're getting both of those figures with an empty ICPS?
« Last Edit: 08/01/2019 08:04 am by jadebenn »

Offline jadebenn

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Re: NASA's Artemis Program Updates and Discussion Thread 3
« Reply #46 on: 08/01/2019 08:07 am »
The original approach was reusable.

Now with 2024 objective expendable is allowed for a Mark I version of the architecture, the sustainable, reusable version coming later.

With the usual risk to be stuck with the first one. How to justify to develop a new architecture when you have one which works?

As a European I could provide the example of Ariane 5 ECA which was supposed to be an interim solution waiting for the Vinci engine but I am sure there are many in the US.

As someone who worked in for several years in what was supposed to be a temporary Marine Corps building in Mojave that was built during WWII, I can tell you that there are few things more permanent than a temporary solution...

IOW, I totally agree with your concern. If we skip reusability for speed, it'll just make things easier to cancel down the road. Lander reusability doesn't have to be that hard either. There are several ways to get it from day one without requiring a lot of headache.

~Jon
If NASA starts relaxing the requirements for later landers: start worrying. Otherwise I think we're fine. If the engineers know it's going to be a part of the design from the get-go, they'll factor that into the initial design, so that they're not having to re-do the whole thing a few years afterwards.

Offline Steven Pietrobon

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Re: NASA's Artemis Program Updates and Discussion Thread 3
« Reply #47 on: 08/01/2019 08:14 am »
Well now I don't know who to believe.

To clarify, you're getting both of those figures with an empty ICPS?

Payload mass does not include the empty mass of the iCPS (89.0 t). The IMLEO includes the empty mass of the iCPS (89.0+5.2 = 94.2 t).
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline envy887

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Re: NASA's Artemis Program Updates and Discussion Thread 3
« Reply #48 on: 08/01/2019 11:46 am »
Well now I don't know who to believe.

To clarify, you're getting both of those figures with an empty ICPS?

Payload mass does not include the empty mass of the iCPS (89.0 t). The IMLEO includes the empty mass of the iCPS (89.0+5.2 = 94.2 t).

That's with a full duration burn off the ICPS to reach LEO, correct?

Have you run the Block 0 version with no ICPS?

Online JohnFornaro

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Re: NASA's Artemis Program Updates and Discussion Thread 3
« Reply #49 on: 08/01/2019 02:07 pm »
It took me a while before I had the "Duh!" moment on this, but everything makes sense when you realize that the "70 tonnes to LEO" number that's cited for Block 1 SLS means that the SRBs and core can get 70 tonnes to LEO, with no upper stage contribution at all.  That turns out to be close to what ICPS+OSA+ESM+fairings+CM+LAS weighs.  ...

Then the ICPS can get about 27 tonnes to TLI, and that becomes your limit for how heavy the full on-orbit Orion stack can be...

The Orion CM is a relic from the Constellation days...  Throw in a half tonne for the Orion Stage Adapter and you're close to your 27 t limit. ...

And now you see why sinking all that time and effort into supersizing the core stage instead of building a real upper stage was such a waste.

Did I say "build the 70 ton version and start using it"?  Did I?  Why yes, yes I did.
Sometimes I just flat out don't get it.

Online JohnFornaro

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Re: NASA's Artemis Program Updates and Discussion Thread 3
« Reply #50 on: 08/01/2019 02:08 pm »
Except I'm not sure your calculations are right because that "70t to LEO" number is old, old, old and has not been used in any SLS materials for the past 2 years. The modern figure is 95t to LEO.

It's not about the age, it's about the throw weight.
Sometimes I just flat out don't get it.

Online JohnFornaro

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Re: NASA's Artemis Program Updates and Discussion Thread 3
« Reply #51 on: 08/01/2019 02:09 pm »
Except I'm not sure your calculations are right because that "70t to LEO" number is old, old, old and has not been used in any SLS materials for the past 2 years. The modern figure is 95t to LEO.

95 t to LEO assumes the ICPS is depleted to reach 200 km circular LEO. I haven't seen any evidence that the Block 0 version can do 95 t without ICPS. It would be about 75 t but very sensitive to final burnout mass because the core stage is extremely large.

It's close enough!
Sometimes I just flat out don't get it.

Offline envy887

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Re: NASA's Artemis Program Updates and Discussion Thread 3
« Reply #52 on: 08/01/2019 02:42 pm »
It took me a while before I had the "Duh!" moment on this, but everything makes sense when you realize that the "70 tonnes to LEO" number that's cited for Block 1 SLS means that the SRBs and core can get 70 tonnes to LEO, with no upper stage contribution at all.  That turns out to be close to what ICPS+OSA+ESM+fairings+CM+LAS weighs.  ...

Then the ICPS can get about 27 tonnes to TLI, and that becomes your limit for how heavy the full on-orbit Orion stack can be...

The Orion CM is a relic from the Constellation days...  Throw in a half tonne for the Orion Stage Adapter and you're close to your 27 t limit. ...

And now you see why sinking all that time and effort into supersizing the core stage instead of building a real upper stage was such a waste.

Did I say "build the 70 ton version and start using it"?  Did I?  Why yes, yes I did.

Use it for what? There are no 70 ton payloads going to LEO. SLS is pointless without an upper stage.

Online JohnFornaro

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Re: NASA's Artemis Program Updates and Discussion Thread 3
« Reply #53 on: 08/01/2019 03:33 pm »
Did I say "build the 70 ton version and start using it"?  Did I?  Why yes, yes I did.

Use it for what? There are no 70 ton payloads going to LEO. SLS is pointless without an upper stage.

Use it for going to the Moon?  Am I missing something from the thread above?  That 70 tons in LEO is pretty useful?  Which is not to suggest that the gateway, the lander, the transfer vehicle, the lunar base, yada yada yada comes in at 70 tons.
« Last Edit: 08/02/2019 02:14 pm by JohnFornaro »
Sometimes I just flat out don't get it.

Offline envy887

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Re: NASA's Artemis Program Updates and Discussion Thread 3
« Reply #54 on: 08/01/2019 04:28 pm »
Did I say "build the 70 ton version and start using it"?  Did I?  Why yes, yes I did.

Use it for what? There are no 70 ton payloads going to LEO. SLS is pointless without an upper stage.

Us it for going to the Moon?  Am I missing something from the thread above?  That 70 tons in LEO is pretty useful?  Which is not to suggest that the gateway, the lander, the transfer vehicle, the lunar base, yada yad yada comes in at 70 tons.

All of that requires an upper stage, because none of it is actually going to LEO. The 70 tons to LEO with no upper stage spec is pointless, which is why NASA didn't even bother with Block 0.

The only reason to use a HLV to get to LEO is so Orion can do ISS crew rotations. But that's an exorbitantly expensive waste of Orion's BLEO capabilities, and also only requires a 35 t to LEO launcher, not a 70 t launcher.

Offline A_M_Swallow

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Re: NASA's Artemis Program Updates and Discussion Thread 3
« Reply #55 on: 08/01/2019 04:46 pm »
Did I say "build the 70 ton version and start using it"?  Did I?  Why yes, yes I did.

Use it for what? There are no 70 ton payloads going to LEO. SLS is pointless without an upper stage.

Us it for going to the Moon?  Am I missing something from the thread above?  That 70 tons in LEO is pretty useful?  Which is not to suggest that the gateway, the lander, the transfer vehicle, the lunar base, yada yad yada comes in at 70 tons.

All of that requires an upper stage, because none of it is actually going to LEO. The 70 tons to LEO with no upper stage spec is pointless, which is why NASA didn't even bother with Block 0.

The only reason to use a HLV to get to LEO is so Orion can do ISS crew rotations. But that's an exorbitantly expensive waste of Orion's BLEO capabilities, and also only requires a 35 t to LEO launcher, not a 70 t launcher.

To move stuff from LEO to lunar orbit an upper stage is not needed since a reusable space tug can do that job. A couple of RL-10 or methane burning Broadsword engines could power the tug.

Offline TheRadicalModerate

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Re: NASA's Artemis Program Updates and Discussion Thread 3
« Reply #56 on: 08/01/2019 05:00 pm »
Did I say "build the 70 ton version and start using it"?  Did I?  Why yes, yes I did.

Use it for what? There are no 70 ton payloads going to LEO. SLS is pointless without an upper stage.

Us it for going to the Moon?  Am I missing something from the thread above?  That 70 tons in LEO is pretty useful?  Which is not to suggest that the gateway, the lander, the transfer vehicle, the lunar base, yada yad yada comes in at 70 tons.

Here's my guess at how this got so confusing:

In the beginning, nobody at MSFC could imagine SLS ever being used in a pure LEO mission.  They assumed (quite correctly) that all viable SLS profiles were for BEO missions.  So when they were initially asked for payload to LEO, they assumed that what they were really being asked was, "How big is the stack that you're putting into a parking orbit prior to TLI?"  And so they said, "70 tonnes," and that was that.

Then SpaceX came along with FH, and advertised 63 t to LEO.  An obvious criticism of SLS Block 1 was then, "You're going to spend north of $2B a launch and your megarocket only puts 7 tonnes more into LEO than the SpaceX dealywhobber that costs $150M a launch????"

So MSFC realized they had a PR problem, and they fixed it by coming up with a pure LEO number, which is somewhere in the >90 t range if you get all the way to ICPS burnout.  Never mind that there's no fairing for such a launch, and no plans ever to do one.  Now they have a number to fend off SpaceX.

Does it matter how much SLS can throw to your standard 200 x 200 x 28.5 LEO?  Absolutely not--the parking orbit is all we care about.  But that doesn't mean that the SLS guys don't have to measure their... rockets... against all the other guys'... rockets.
« Last Edit: 08/01/2019 05:00 pm by TheRadicalModerate »

Offline whitelancer64

The SLS's parking orbit is 200 km x 1800 km (or so)

For a 1-1 comparison, what could Falcon Heavy put into such an orbit?
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Offline TheRadicalModerate

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Re: NASA's Artemis Program Updates and Discussion Thread 3
« Reply #58 on: 08/01/2019 05:18 pm »

To move stuff from LEO to lunar orbit an upper stage is not needed since a reusable space tug can do that job. A couple of RL-10 or methane burning Broadsword engines could power the tug.

You're basically describing Block 1B, where EUS is a combination of "tug" and "real live second stage like the big boys use on their rockets".

Now, if you're talking about a real reusable tug that does earth-orbit rendezvous with its payload and hauls it somewhere interesting (i.e., a piece of hardware that doesn't currently exist), I can't think of a reason to use SLS.  If you can dream up a 95-tonne payload that a tug can actually handle, you can likely dream up a way of dividing that payload into two pieces and launching it on something that costs vastly less than >$2B a pop.

Offline TheRadicalModerate

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Re: NASA's Artemis Program Updates and Discussion Thread 3
« Reply #59 on: 08/01/2019 05:30 pm »
The SLS's parking orbit is 200 km x 1800 km (or so)

For a 1-1 comparison, what could Falcon Heavy put into such an orbit?

200 x 1800 is about 410 m/s more energy than 200 x 200.  By my model, an FHE could put 55 t into that orbit.

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