[New] Space Launch System / Orion Discussion Thread

[Meecrob]

By the above logic, it was "irresponsible" to pursue anything larger than ancient Chinese black powder rockets.

[ZooNamedGames]

17 minutes ago, Meecrob said:

By the above logic, it was "irresponsible" to pursue anything larger than ancient Chinese black powder rockets.

Except we used them and knew what would happen? It’s scaling up by leagues instead of incrementally that’s the problem.

[sh1pman]

1 hour ago, ZooNamedGames said:

don’t have is the knowledge of how those vehicles will behave under the circumstances of acceleration

Fortunately, centrifuges exist. 

[tater]

1 hour ago, ZooNamedGames said:

It’s only weaker with larger builds due to the increased stresses involved- and its not that we can’t but that we aren’t prepared for what we don’t know with such scales. Could we make a massive multijoint vessel with 8 modules to speed off to Mars? Yes, we have the vehicles and the technology to do so- what we don’t have is the knowledge of how those vehicles will behave under the circumstances of acceleration, deep space flight or anything else since we haven’t made something to those scales. We don’t know what could happen- not that those make it impossible to do- just irresponsible to take risks and to wave potential unknowns just because we’ve done something far smaller and simpler than such a larger task as I described.

This makes no sense at all. They know the specs on the docking adapters. They are either good enough, or they improve them. It's trivial.

I find it bizarre that testing via doing it is required for this one aspect of SLS/Orion, yet for the rest, modelling and part testing on the ground is fine (yet other entities testing by flying and iteration (the same thing) are somehow bad, and will take longer (because "not Lockheed Martin" is doing it).

It's a docking port under compression. at something on the order of 1g. It's not a big deal, and can (and has been, I'm sure) modeled.

[Nightside]

1 hour ago, Meecrob said:

By the above logic, it was "irresponsible" to pursue anything larger than ancient Chinese black powder rockets.

This may be true...

[tater]

2 hours ago, ZooNamedGames said:

Except we used them and knew what would happen? It’s scaling up by leagues instead of incrementally that’s the problem.

There's nothing about docking two things together and placing them under acceleration along the long axis through the docking port that is incredibly esoteric. Unknown territory would be docking 2 things, then spinning them for gravity, for example, that would require extensive modeling, assuming the current docking system could even do it. The docking mecanism works in a hard dock via hooks that pull the two vehicles into compression, and lock it. Adding marginally more compression... not a big deal. (note if they wanted to, they'd redesign it for even that case, and test it via modeling)

 

I'd add that NASA Design Reference Missions for Mars have had Orion stuck at the front, or on the SIDE of vehicles expected to do a TMI, then TEI burn. Not an issue, unless NASA was clueless when they did those mission architectures.

Edited September 14, 2019 by tater

[ZooNamedGames]

2 hours ago, sh1pman said:

Fortunately, centrifuges exist. 

The size of the ISS?

[tater]

NASA seems to think you can "travel" with Orion stuck in both compression, and sheer on a docking port. Go figure.

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20160014801.pdf

[sh1pman]

17 minutes ago, ZooNamedGames said:

The size of the ISS?

Just test the weak parts. Docking rings and connections. Mass can be simulated with concrete blocks.

[Meecrob]

On 9/13/2019 at 9:58 PM, ZooNamedGames said:

The size of the ISS?

In this case, size/mass does not matter. Physics is pretty cool that way. If I push 1kg with 1N of force, it will accelerate at 1m/s². If I push 2kg with 2N of force, it will accelerate at 1m/s². If I push 1,000,000kg with 1,000,000N, it will accelerate at 1m/s². I have never actually done any of these examples myself, but I know the answer with certainty because it is a physical law. It MUST be true. For example, Japan has many skyscrapers that are designed to be earthquake-resistant, yet also has many small structures that are completely destroyed by earthquakes. The size/mass of the building has nothing to do with earthquake-resistance. All that matters is that over a certain acceleration, structural integrity is compromised. Now lets say you have a hypothetical spaceship that accelerates at the same rate that a typical earthquake does. You could radially attach that skyscraper to your ship, and it would withstand the ship's acceleration, no problem, but if you attached the small structure not designed to be earthquake-resistant, it would fail under the ship's acceleration.

On 9/13/2019 at 7:39 PM, ZooNamedGames said:

It’s scaling up by leagues instead of incrementally that’s the problem.

I would propose that we are not scaling up at all. It may be easier to look at it as a ratio or fraction. Let Apollo mass (Saturn V + LM + Service Module, etc.) be x and the thrust it required to perform its mission be y. We can say that x/y = Successful Moon Landing. Now lets say we want to send 10x the mass of Apollo on the exact same mission. All other things being equal (Earth escape, TLI, Lunar capture, etc Delta-V), we would deduce that in order to send 10x to "Successful Moon Landing", we require 10y, thus 10x/10y = Successful Moon Landing. But 10x/10y = x/y. The numbers (mass, thrust) may change, but their ratio to eachother is the same and therefore the forces applied are also the same. Both Apollo and "10x Apollo" would have the exact same Delta-V, Thrust to Weight, burn times, orbital period, etc.

 

 

On 9/13/2019 at 8:47 PM, Nightside said:

This may be true...

Haha, touche

[Nightside]

 

21 hours ago, Meecrob said:

In this case, size/mass does not matter. Physics is pretty cool that way. If I push 1kg with 1N of force, it will accelerate at 1m/s². If I push 2kg with 2N of force, it will accelerate at 1m/s². If I push 1,000,000kg with 1,000,000N, it will accelerate at 1m/s².

Axial thrust isn’t really the limitation, it is oscillations between structures. Of particular concern is a situation where oscillations resonate with the natural frequency of a structure.

21 hours ago, Meecrob said:

Japan has many skyscrapers that are designed to be earthquake-resistant, yet also has many small structures that are completely destroyed by earthquakes. The size/mass of the building has nothing to do with earthquake-resistance.

The force applied does not need to be large enough to destroy the structure all at once. Resonant oscillations are the trouble maker.

A building (or other structure) can be considered as a lollipop, a mass on a stiff spring attached to the ground. If the ground is accelerated in a single burst, the mass will oscillate with a frequency that is defined by its mass, the length of the spring and the stiffness of the spring, this is its natural frequency. 

Of course earthquakes don't come as a single burst, but as waves, and waves have a frequency.  If this frequency is close to the natural frequency of a structure, then the structure will get pushed further and further over with each wave, eventually this is what will topple buildings. Since most structures in a region may be made of similar materials, height is the main differentiating factor. A given earthquake may have a frequency that topples only midrise buildings, but leaves homes and skyscrapers unscathed.  

Because of their sized and cost, skyscrapers and other large buildings are designed to have a natural resonance outside of the expected earthquake accelerations, for extreme cases like Tapei 101 (built on a fault system) they will even something like a Tuned Mass Damper to reduce the shaking in the upper floors.

 

For a spacecraft, the driving oscillations (from an engine) should be easier to study and determine, but the natural frequency of the structure could change over different mission profiles and combinations of different spacecraft docked to each other. 
All of which is to say that mass (and placement thereof) definitely matter, but also that these are issues that are probably addressed on all spacecraft that have propulsion, especially those with large solar trusses and antenna arrays. 

Edited September 16, 2019 by Nightside
gave up typing on phone

[tater]

We're not taling about huge structures here, we're talking about a lunar lander docked to Orion---an eventuality that I'm sure was considered given that a large lander (Altair) was prat of the Constellation Program from which Orion came, and it was precisely an EoR architecture (since even then Orion had an anemic SM, and Altair had to do much of the work).

[Xd the great]

2 hours ago, tater said:

We're not taling about huge structures here, we're talking about a lunar lander docked to Orion---an eventuality that I'm sure was considered given that a large lander (Altair) was prat of the Constellation Program from which Orion came, and it was precisely an EoR architecture (since even then Orion had an anemic SM, and Altair had to do much of the work).

The biggest problem is can the 10,000N required to push the Orion be successfully transferred through a docking port.

[StrandedonEarth]

6 minutes ago, Xd the great said:

The biggest problem is can the 10,000N required to push the Orion be successfully transferred through a docking port.

That’s just an engineering problem, and a relatively simple one (compared to creating these vessels in the first place) at that. There is no reason it can’t be solved, if it hasn’t been already. 

MOAR STRUTS!

[tater]

35 minutes ago, Xd the great said:

The biggest problem is can the 10,000N required to push the Orion be successfully transferred through a docking port.

Altair was supposed to do the LOI burn with Orion (called MPCV at the time) attached.

[ZooNamedGames]

3 hours ago, tater said:

Altair was supposed to do the LOI burn with Orion (called MPCV at the time) attached.

NASA left a lot up to the post concept phase. I’m still wondering how they intended to side-heft a X-15 in those early concepts for an orbital X-15 using the Navajo missile. So something tells me they don’t do all the math and sometime just design things to do what they think will work based on back of the envelope calculations. Which is likely the case for NASA concepts like Altair and Copernicus and any asymmetric builds joined together but docking ports. 

Edited September 17, 2019 by ZooNamedGames

[tater]

Lander stacks are not asymmetric.

Just to be clear: You are saying that Orion is an even worse vehicle than we thought, and it cannot ever be used docked to anything capable of acceleration?

Wow, Orion is worse than I thought, and all those NASA claims of using it for Mars are just so much BS, I guess (if it can't dock to something doing a TLI burn, it can't dock to anything doing a TMI burn, either).

Edited September 17, 2019 by tater

[KSK]

5 hours ago, Xd the great said:

The biggest problem is can the 10,000N required to push the Orion be successfully transferred through a docking port.

Apollo 13 says hi.

PC+2 burn to expedite return journey to Earth performed by lunar module descent engine, putting out around 45,000N. That was also the 'shaved to within an inch of it's life to save weight' spacecraft pushing the substantially heavier CSM through its docking port, without crumpling like a beer can in the process. 

Oh - and the descent engine, or DPS, was indeed used at full throttle. From the flight journal on NASA's own history site.

077:55:24 Brand: Okay. This is P30, LM maneuver PAD, PC plus 2 hours, starting with Noun 33, 079:27:38.30; plus 0833.0, minus 0050.9, minus 0213.9; N/A, plus 0020.5; 0861.5, 4:24; 272, 081; and the rest is N/A except for comments as follows. Ullage, two jets, 10 seconds; CSM weight, 62480; LM weight, 33452 and the DPS throttle profile is the same as before, 5 seconds at minimum, 21 seconds at 40 percent, and the remainder of the time at Max. Over.

077:56:02 Haise: Okay, Vance. [Garble] 079:27:38.30; plus 0833.0, minus 0050.9, minus 0213.9; N/A, plus 0020.5; 0861.5, 4:24, 272, 081; and the rest N/A. Ullage, two jets, 10 seconds; CSM weight, 62480; LM weight, 33452. DPS throttle profile same as before, 5 seconds, 40 percent for 21 seconds, 40 percent, and the remainder at Max throttle [garble]. [Long pause.]

Emphasis added.

Edit the 2nd. The 'LM lifeboat' concept had also been tested on Apollo 9, including the use of the LM to push the CSM. So this was something that had been prepared and planned for beforehand - it wasn't a last ditch manoeuvre to get the Apollo 13 crew home.

Edited September 17, 2019 by KSK

[ZooNamedGames]

10 hours ago, KSK said:

Apollo 13 says hi.

PC+2 burn to expedite return journey to Earth performed by lunar module descent engine, putting out around 45,000N. That was also the 'shaved to within an inch of it's life to save weight' spacecraft pushing the substantially heavier CSM through its docking port, without crumpling like a beer can in the process. 

Oh - and the descent engine, or DPS, was indeed used at full throttle. From the flight journal on NASA's own history site.

077:55:24 Brand: Okay. This is P30, LM maneuver PAD, PC plus 2 hours, starting with Noun 33, 079:27:38.30; plus 0833.0, minus 0050.9, minus 0213.9; N/A, plus 0020.5; 0861.5, 4:24; 272, 081; and the rest is N/A except for comments as follows. Ullage, two jets, 10 seconds; CSM weight, 62480; LM weight, 33452 and the DPS throttle profile is the same as before, 5 seconds at minimum, 21 seconds at 40 percent, and the remainder of the time at Max. Over.

077:56:02 Haise: Okay, Vance. [Garble] 079:27:38.30; plus 0833.0, minus 0050.9, minus 0213.9; N/A, plus 0020.5; 0861.5, 4:24, 272, 081; and the rest N/A. Ullage, two jets, 10 seconds; CSM weight, 62480; LM weight, 33452. DPS throttle profile same as before, 5 seconds, 40 percent for 21 seconds, 40 percent, and the remainder at Max throttle [garble]. [Long pause.]

Emphasis added.

Edit the 2nd. The 'LM lifeboat' concept had also been tested on Apollo 9, including the use of the LM to push the CSM. So this was something that had been prepared and planned for beforehand - it wasn't a last ditch manoeuvre to get the Apollo 13 crew home.

Apollo- inline thrust. 

Copernicus- asymmetric thrust. 

[Barzon]

10 minutes ago, ZooNamedGames said:

Copernicus- asymmetric thrust. 

How so?

The Orion docked on the underside would remain in LEO or return, iirc. The only Orion on the Mars trip was mounted inline, at the front of the vehicle.l,

[KSK]

17 minutes ago, ZooNamedGames said:

Apollo- inline thrust. 

Copernicus- asymmetric thrust. 

I was replying to the following:

18 hours ago, tater said:

We're not taling about huge structures here, we're talking about a lunar lander docked to Orion---an eventuality that I'm sure was considered given that a large lander (Altair) was prat of the Constellation Program from which Orion came, and it was precisely an EoR architecture (since even then Orion had an anemic SM, and Altair had to do much of the work).

And then XD the Great's reply that "the biggest problem is can the 10,000N required to push the Orion be successfully transferred through a docking port."

 

 

[tater]

There is nothing asymmetric about any thrust structure associated with Artemis landers.

It's basically Altair with a round descent stage. Orion would dock at the top (where the docking port is).

16 minutes ago, Barzon said:

How so?

The Orion docked on the underside would remain in LEO or return, iirc. The only Orion on the Mars trip was mounted inline, at the front of the vehicle.l,

Yeah, that's true, it's from when Orion was MPCV, and only needed a lousy SM because it was to be used the only place it belongs as a CSM by itself (LEO).

Regardless, Orion would be under compression at the docking port from the TMI burn.

[tater]

 

[ZooNamedGames]

The exact idea I’ve felt about it since the beginning. Set a challenging goal so we have to work hard to meet it and even if we fall short- it’s miles further than we were before.

[tater]

12 minutes ago, ZooNamedGames said:

The exact idea I’ve felt about it since the beginning. Set a challenging goal so we have to work hard to meet it and even if we fall short- it’s miles further than we were before.

Um, no.

So she's saying that she thinks that the fact that the majority of launches are commercial is somehow less efficient. She's delusional. Minus commercial launches Artemis reaches the Moon, let's see, multiply by.... add... carry the 2...

Never.