totm dec 2023 Artemis Discussion Thread

[jinnantonix]

1 hour ago, ThatGuyWithALongUsername said:

*coughs* https://m.xkcd.com/1244/

LOL.  Why?  Because it offends the purists that a game might have any value as a simulation tool.  That is not saying that it beats real calculations by experienced engineers.

Edit:  And BTW the testing was just to confirm that it is feasible to complete a "reasonably" controlled landing of a 6.5t payload on the moon with a single AJ10-190 OMS (~27kN thrust).

Edited October 28, 2019 by jinnantonix

[ThatGuyWithALongUsername]

47 minutes ago, jinnantonix said:

LOL.  Why?  Because it offends the purists that a game might have any value as a simulation tool.  That is not saying that it beats real calculations by experienced engineers.

Woah there, it's just a webcomic. It's perfectly fine to try random concepts like this in KSP, I've done it before even. I'm just saying there's a *lot* of stuff KSP doesn't simulate, even with RSS/RO, so don't take it fr granted- which you're not.

[jinnantonix]

Hey, no worries, I know i's just a webcomic.  I actually agree that KSP simulations shouldn't be taken too seriously, just making the point that within the bounds of discussion here they are useful illustrations of what is possible and what is not.

[tater]

The simulation of finances in KSP is far, far worse than the simulation of spacecraft (as zeroith order as even that is). The issue is money. If they don't start throwing real money at the traditional contractors, it stays paper. I can see BO working on their part, regardless, heck, I could imagine them buying the ascent stage if needed. Boeing? They're not moving past powerpoint unless they are given a semi-truck full of money first, and right now that seems pretty unlikely. What is the lander likely to get right now, 300M$ split 2 ways?

[jinnantonix]

On 10/25/2019 at 4:44 AM, sevenperforce said:

...the cost to get from TLI to LOP-G is not 800 m/s; that's the round-trip cost for Orion. If you are making a one-way trip from TLI to LOP-G, you only need a 183 m/s powered lunar flyby and a 215 m/s NRHO insertion burn, for a total of ~400 m/s. See page 5 of this paper. I was allowing 430 m/s as this is the value cited in some other papers.

Note that it is not possible to model this in KSP, because there is no such thing as a Lagrange point.  So NRHO cannot be simulated.   Therefore  optimal approach cannot be replicated. 

 

[tater]

 

 

[IncongruousGoat]

5 hours ago, jinnantonix said:

Note that it is not possible to model this in KSP, because there is no such thing as a Lagrange point.  So NRHO cannot be simulated.   Therefore  optimal approach cannot be replicated.

Without Principia, that is.

[tater]

 

[tater]

 

[tater]

 

[sevenperforce]

7 hours ago, jinnantonix said:

Note that it is not possible to model this in KSP, because there is no such thing as a Lagrange point.  So NRHO cannot be simulated.   Therefore  optimal approach cannot be replicated. 

You cannot exactly simulate NRHO but you can model it by placing your station in a circular orbit at 12 million km, slightly ahead of the Mun, with an inclination of about 12 degrees. You'll librate up and down in front of the Mun but never enter its SOI.

48 minutes ago, tater said:

 

Seen on Twitter -- new plan, each astronaut swallows 7 kg of moon rocks.....

[jadebenn]

5 hours ago, tater said:

 

I think this tweet chain distills exactly why I dislike Eric Berger's reporting.

Edited October 29, 2019 by jadebenn

[tater]

12 minutes ago, jadebenn said:

I think this tweet chain distills exactly why I dislike Eric Berger's reporting.

I thought it was amusing.

Then again, I find SLS/Orion amusing/comical (which is deeply sad, I would much prefer to be inspired by such a program, but that is completely impossible). For all the problems that I had with Shuttle, it was novel, and pushed the envelope. SLS/Orion is best at nothing at all. Best at being cut-rate Apollo, maybe? Better toilet facilities than Apollo, it's got that going for it (which to be fair is a non-trivial improvement). Regardless, they've had years, and many, many billions of dollars, they should have characterized sample return logistics ages ago.

[tater]

 

[tater]

 

[jinnantonix]

Here is a KSP simulation of Artemis 3 mission proposed for mid 2024, with a lunar lander comprising a re-usable habitat pod and an expendable transit vehicle which is fully integrated at launch.  No refuelling is required.  The vehicle has a mass of 44 tons at launch and includes a single AJ10-190 OMS engine at 26.7 kN thrust and Isp = 319.  The re-usable lander habitat pod  is a variant of the Orion pressure vessel using same jigs and construction methodology, smaller and lighter, and with extra thrusters for return from the moon from LLO to NHRO.  The lunar lander is delivered using two Falcon Heavy launches: the first launch gets the craft to LEO, the second launch has a payload comprising a small docking unit with avionics to allow remote controlled docking of the FH second stage with the lander in LEO.  This docked craft thrusts to 70% of TLI.  The lander then uses it's own engine to proceed to the LOP-G.  Subsequent missions launch the same expendable craft, minus the habitat pod, which docks at the LOP-G.

Edit:  A big thanks to @sevenperforce for the fundamental concepts in the mission design.

 

 

Edited November 3, 2019 by jinnantonix

[jinnantonix]

Not shown in the above video. 

• When the Ascent Vehicle/habitat pod reaches LOP-G after the lunar surface mission it still has an empty inline drop tank attached.  This design proposes that prior to the crew returning to Earth, the empty Cygnus logistics module is used to dock with this drop tank, and detach it from the AV.  The Cygnus then decelerates for lunar impact and disposal.
• Considering the several docking procedures required at LOP-G it makes sense that the Canadarm be available, potentially delivered on the Artemis 2 mission,
• Subsequent missions use exactly the same process, except the habitat pod remains at the LOP-G and is re-used.  An avionics module with docking port is used to remote control transfer the expendable assembly from Earth to the LOP-G for each mission.

Additional thought.  During the descent phase the last radial drop tanks are ejected about 1000m above the surface.  It is important that at this late stage of the descent, that the descent vehicle will need to have some lateral velocity, otherwise the craft may encounter debris at the landing zone.  Even so, after several proposed lunar landings in the Shackleton Crater, these drop tanks will be randomly littering the surface.  It may make more sense to land with the descent vehicle drop tanks still attached.

Edited November 2, 2019 by jinnantonix

[jadebenn]

@jinnantonix One minor error I noticed in your video: The SLS's LES and the Orion fairing panels should stage before the EUS fires up its engines, not after.

Edited November 2, 2019 by jadebenn

[Retro Starship]

7 hours ago, jinnantonix said:

Here is a KSP simulation of Artemis 3 mission proposed for mid 2024

That is just awesome @jinnantonix!! I saved both this video as well as @tater stunning Artemis videos in my youtube addto's. Man this is going to be so cool!  

[sevenperforce]

On 11/2/2019 at 2:28 AM, jinnantonix said:

Not shown in the above video. 

• When the Ascent Vehicle/habitat pod reaches LOP-G after the lunar surface mission it still has an empty inline drop tank attached.  This design proposes that prior to the crew returning to Earth, the empty Cygnus logistics module is used to dock with this drop tank, and detach it from the AV.  The Cygnus then decelerates for lunar impact and disposal.
• Considering the several docking procedures required at LOP-G it makes sense that the Canadarm be available, potentially delivered on the Artemis 2 mission,
• Subsequent missions use exactly the same process, except the habitat pod remains at the LOP-G and is re-used.  An avionics module with docking port is used to remote control transfer the expendable assembly from Earth to the LOP-G for each mission.

Additional thought.  During the descent phase the last radial drop tanks are ejected about 1000m above the surface.  It is important that at this late stage of the descent, that the descent vehicle will need to have some lateral velocity, otherwise the craft may encounter debris at the landing zone.  Even so, after several proposed lunar landings in the Shackleton Crater, these drop tanks will be randomly littering the surface.  It may make more sense to land with the descent vehicle drop tanks still attached.

Loved it!

Nice job with figuring a way to dispose of the hab drop tank. I had struggled with this. Your solution permits a nice closed-loop sortie without necessarily needing the Canadarm, though having one is obviously a good idea.

Did you consider reducing the number of drop tanks and using the Falcon upper stage to perform the powered flyby and LOP-G insertion?

Landing with the drop tanks still attached makes for a rather surprisingly higher landed mass. The drop tanks will have 1-2% residual props and their added weight means the landing legs and structure needs to be heavier. Additionally, that extra weight during the landing means more propellant utilization for the ascent stage, which means a bigger ascent stage tank, which increases mass all the way up. Hovering is the most wasteful part of the whole event so you want absolute minimum mass for the hover. Using lateral velocity disposal seems ideal if it can be managed.

[jinnantonix]

6 hours ago, sevenperforce said:

Did you consider reducing the number of drop tanks and using the Falcon upper stage to perform the powered flyby and LOP-G insertion?

The drop tank layout used here just fits inside the standard Falcon Heavy fairing shell, but it can definitely be improved to reduce the number of drop tanks.  Double sized tanks, two tanks each for the TLI-NRHO and NRHO-LLO and LLO-Surface tank drops would be feasible.  Two drop tanks ejected prior to landing would reduce surface debris litter.

The Falcon upper stage does not have sufficient fuel to reach TLI, let alone do the fly-by and LOP-G insertion.  I would imagine hydrogen boil off would play a part in that calculation.  Doing all the FH burns within a few hours of launch eliminates any issues and risks around that.

Note that the FH upper stage for the lunar lander launch has some fuel remaining after reaching LEO, which could potentially be used, giving the craft a little extra boost - still nowhere near enough to get the lunar lander to TLI, the OMS still needs to do 3 burns and provide the 44 ton craft approx dV =1500 m/s  to get to NRHO.

 

Edited November 4, 2019 by jinnantonix

[mikegarrison]

I'm not sure I understand how "drop tanks" and "reuseable lander" go together. I guess the next flight brings more drop tanks and then they have to be attached to the lander in lunar orbit? This seems very challenging. It's also an absolutely critical failure point, because if anything goes wrong and the lander does not have enough useable fuel to get back to the LOP-G, the crew is probably dead.

Edited November 5, 2019 by mikegarrison

[kerbiloid]

2 hours ago, mikegarrison said:

I'm not sure I understand how "drop tanks" and "reuseable lander" go together.

Spoiler

 

2 hours ago, mikegarrison said:

attached to the lander in lunar orbit? This seems very challenging. It's also an absolutely critical failure point, because if anything goes wrong and the lander does not have enough useable fuel to get back to the LOP-G, the crew is probably dead.

Anyway not as deadly as flying to Mars and going to return on locally produced methane.

[mikegarrison]

13 minutes ago, kerbiloid said:

Anyway not as deadly as flying to Mars and going to return on locally produced methane.

Presumably one would not *start* flying to Mars unless it was known the methane was already produced.

[kerbiloid]

1 hour ago, mikegarrison said:

Presumably one would not *start* flying to Mars unless it was known the methane was already produced.

1. How could they know that the produced is actually methane, and it will survive in cryotanks for two years until their return.
2. They either need a refuel action on another planet, or returning on a ship which is waiting for them in vacuum and dust storms on another planet with permanently working ISRU euipment.

(An offtopic starts here in sense of Artemis.)
 

Spoiler

Anyway I believe that until they have a fully reusable rocket delivering 80 t to the lunar surface the whole lunar idea makes not much sense.
While having it they can not just deliver heavy equipment to build a serious base, but also can have:

A lunar base with ice mining on surface. Crew of 12 (2 x 6).

A refuel station on lunar orbit. Crew of 3.

A fully reusable sixpack-crew lander with no expendable/reattachable parts and bimodal propulsion unit: ammolox/hypergolics.
Delivers surface crew in shifts by 6, to let the surface station always have some personnel.
So, there are always two landers parked at the surface base. (And probably one more as a backup).

A long-lasting interorbital tanker-tug with bimodal propulsion unit: hydrolox/ammolox.

Having such rocket they can deliver water and liquid oxygen from the Moon, ammonia and UDMH from the Eath, easily produce NTO onboard from the terrestrial ammonia and lunar oxygen.

Then the scheme could be:

***

Orbital tanker-tug is on LEO. It has full hydrolox tanks and empty water tank.

Lunar base stands on the Moon and has tanks full of water and an electrolysis plant and HTP plant.

Two similar lunar tankers stand at the base. One with water tank on top as payload, another one with liquid oxyfen tank. They are two to make all landers have similar docking mass.
They are ~100t heavy on launch and ~60 t heavy on docking.
Though if the water and the oxygen can be delivered in same tank, then just one lunar tanker makes two flights per expedition.
A lunar tanker has unimodal hydrolox propulsion unit and is fueled with lunar hydrolox and lunar HTP for RCS needs.
It delivers to the orbital station lunar water, liquid oxygen made of lunar water, and lunar HTP.

Lunar lander of the previous crew stands at the base.
It's fully reusable, with no expendable parts, and has a bimodal propulsion unit: ammolox to land + UDMH/NTO to launch and dock.

***

The lunar tanker carrying water and HTP starts (by hydrolox engine) and docks to the orbital station.
It pumps the water and HTP into the station tanks and returns to the surface.
As the whole procedure takes just several hours, it spends only hydrolox and HTP.

The lunar tanker carrying liquid oxygen does the same.

Now the orbital station is full of water, liquid oxygen, and HTP.

*

Reusable LV starts from the Earth and delivers to the tanker-tug on LEO the only expendable part of it: a cistern of liquid ammonia with attached tank of UDMH.
The LV upper stage returns.

The tanker-tug spends the hydrogen and a half of oxygen for lunar transfer (by hydrolox engine).
On arrival it spends some part of ammonia and the rest of oxygen for lunar insertion and rendez-vous with the lunar orbital station (by ammolox engine). It docks.

It pumps UDMH and most part of ammonia into the station tanks.

Now the orbital station is full of water, liquid oxygen, HTP, liquid ammonia, and UDMH.

*

The orbital station starts producing NTO from the terrestrial ammonia and the lunar oxygen.
It's simple as both components have already been purified on surface.

The interorbital tanker-tug now has onboard remains of liquid ammonia.
It takes corresponding amount of the lunar liquid oxygen and it fills its empty water tank with lunar water.

*

The interorbital tanker-tug starts to the Earth spending the rest of ammonia and the lunar oxygen (by ammolox engine).
It takes 3..4 days to reach the LEO. So, the tanker-tug engages its powerplant (if it's a small nuke similar to the Soviet ones) and the electrolysis plant.
While it's flying to the Earth, it partially splits the lunar water and refuels the hydrolox tanks.

It jettisons the expendable ammonia+UDMH part and lets it burn in the atmosphere.

On arrival it engages hydrolox engines and inserts LEO.
It vents hydrolox tanks.

Now it has empty LH2 and LO2 tanks, and a partially filled water tank.

It sleeps in LEO until the next expedition.
Then, several days before the next LV launch it splits the lunar water and refills the hydrolox tanks preparing to the ammonia delivering.

So, the orbital tug spends some ammonia from the Earth but everything other from the Moon.

*

The previous lunar crew is on the lunar surface base.
They board the lunar lander standing next to the base.
It has empty ammolox tanks and full UDMH/NTO tanks.

The lander starts and docks to the lunar orbital station.
The crew gets into their Orion(-like) ship and returns to the home.

*

The orbital station crew (the gas station personnel) refuels the docked lander with UDMH (delivered from the Earth by the tug) and NTO (produced onboard from ammonia and oxygen).
Also it checks, tests, so on.

*

The next lunar crew gets from the Earth to the lunar orbital station in the Orion(-like) ship.

The lander gets refueled with ammonia and liquid oxygen. (From the station cryotanks, more appropriate as a storage than thin tanks of the lander).

The lunar crew boards the lander, deorbits and lands at the surface base, spending all ammolox and finishing the landing on hypergolics.
Either they vent the ammolox tanks, or a fuel rover sucks out the ammolox remains.

The lander stays fueled with UDMH/NTO for next three months until they return.

*

So, as they have 2x6 on the surface base, and a shift lasts for standard three months, they have to repeat this every six-seven weeks to deliver the next human sixpack.

Also they can support two lesser bases with no ISRU (just a landed Skylab and a heavy rover with a drill) at once in other random parts of the Moon to study it all.

Then the tanker-tug, the landers, the lunar tankers, the plants, the reusable LV , and the small gas-station crew of the orbital station are always in work, as every two weeks there is another expedition, and nothing just stays and waits.

In this case the Moon geological research will be mostly finished in a couple of decades.
All biological studies (on the main surface base at the South Pole) will be finished even earlier (as it is just to realize is 1/6 g closer to 0 g or to 1 g in sense of biological degradation, nothing more).
And then they can build there a lunar hotel with 1/6 g disneyland and start getting money to pay the collected bills.

 

Edited November 5, 2019 by kerbiloid