totm dec 2023 Artemis Discussion Thread

[jinnantonix]

On 11/15/2019 at 1:23 AM, sevenperforce said:

I am considering whether a dual-engine design is a better solution. The descent burn is extremely long in most of my evaluations...almost to the point that you'd be burning all the way from LLO continuously.

Correct.  The LLO-Surface transit needs more thrust.    My original design had 2 x OMS for this very reason, but I never liked the design because of the issue of gimballing in case of engine failure.  The ascent needs only a single OMS, adding a second OMS reduces overall efficiency and downmass capability.  Currently the design has 8 x R-4D thrusters to transit from LLO to NRHO.  Perhaps add a whole bunch of thrusters mounted on the descent drop tanks?  8 on each tank + 8 on the capsule = 24x 490N =11.7kN.  That should make a difference.  

Alternatively resurrect the larger and more powerful AJ10-137.  Yeh, nah.

 

On 11/15/2019 at 3:10 AM, sevenperforce said:

If the engines are fixed it is very challenging. If they have some gimbal, it's a little easier, because you can compensate through both gimbal and differential throttling.

This is sort of where I'm thinking....

With drop tanks installed, the descent module almost exactly fills out the Falcon 9 fairing, horizontally. 

Ok so like a big Lockheed Martin type lander can.  Looks a lot like  the AV in my original design. https://www.youtube.com/watch?v=UUWHgPYjFME&t=61s , except much bigger.

Problem:  Add the drop tanks, and the volume increases dramatically.  It's a tricky problem to get it all into a Falcon standard fairing, even horizontally.

 

Edited November 16, 2019 by jinnantonix

[jinnantonix]

Quote

Perhaps add a whole bunch of thrusters mounted on the descent drop tanks?  8 on each tank + 8 on the capsule = 24x 490N =11.7kN.  That should make a difference.  

Tested, and this works perfectly with MJ automation, provided the landing begins at >150km altitude.  The 16x R-4Ds burn at full thrust all the way from orbit to surface (about 20 minutes) and the OMS gently throttles down from around 30km altitude, to landing at around 43% throttle.  Instead of mounting the thrusters on the drop tanks which adds stresses to the radial decouplers, I think the best location would be to mount the R-4D thrusters around the base of the AJ10-190 OMS thermal protection skirt, so the thrusters are left on the lunar surface.   Although I never intended it at the outset, it turns out that this makes the descent vehicle engine layout near identical to the Orion Service Module.  And the re-usable capsule is a full sized 5m diameter Orion pressure vessel with internal airlock.  NASA would love it!
 

EDIT:  Improved design:
 

 

 

Edited November 19, 2019 by jinnantonix

[sevenperforce]

13 hours ago, jinnantonix said:

Correct.  The LLO-Surface transit needs more thrust.    My original design had 2 x OMS for this very reason, but I never liked the design because of the issue of gimballing in case of engine failure.  The ascent needs only a single OMS, adding a second OMS reduces overall efficiency and downmass capability.  Currently the design has 8 x R-4D thrusters to transit from LLO to NRHO.  Perhaps add a whole bunch of thrusters mounted on the descent drop tanks?  8 on each tank + 8 on the capsule = 24x 490N =11.7kN.  That should make a difference.  

Alternatively resurrect the larger and more powerful AJ10-137.  Yeh, nah.

In theory you could spam thrusters around the skirt and use them for hover, translation, and landing with the ascent engine off. That would obviate the need for a frag shield on the main engine or deep throttling. Then maybe go with a Superdraco or a generally thrustier engine.

13 hours ago, jinnantonix said:

Ok so like a big Lockheed Martin type lander can.  Looks a lot like  the AV in my original design. https://www.youtube.com/watch?v=UUWHgPYjFME&t=61s , except much bigger.

Problem:  Add the drop tanks, and the volume increases dramatically.  It's a tricky problem to get it all into a Falcon standard fairing, even horizontally.

This would absolutely require multiple launches. The drop tanks would fall very low.

[jinnantonix]

12 hours ago, sevenperforce said:

In theory you could spam thrusters around the skirt and use them for hover, translation, and landing with the ascent engine off. That would obviate the need for a frag shield on the main engine or deep throttling. Then maybe go with a Superdraco or a generally thrustier engine

I am trying to keep the number of thrusters to a minimum, as each additional R-4D thruster reduces downmass payload capability.  I have found that 16 x R-4D thrusters allows for an efficient LLO-Surface transit.  However the thrusters alone produce only 7.8kN thrust, and this is not enough thrust to hover, the OMS at about 45% of maxthrust is required in addition.   Alternatively the thrusters may be switched off prior to landing, and the OMS throttled to about 75% of maxthrust at landing.

A combination of SuperDRACO and DRACO thruster would also be technically viable, however I really like the OMS and R-4D combination - with the Orion Service module using the exact same engines, this would allow Aerojet Rocketdyne some economy of scale on the engine builds, and so reduces the price per unit and also the overall cost of the Artemis program.

 

 

[jinnantonix]

On 11/15/2019 at 3:10 AM, sevenperforce said:

This is sort of where I'm thinking....

 

How about this?  Exactly the same model as being developed, but replace the Orion pressure vessel with a 3.3m diameter Lochheed Martin -type lander can. 

The model is two Mk1 lander cans, clipped into a scaled up structural tube, add top and bottom docking ports, ladder (need a longer one), and R-4D thrusters (4 x directional and 8 x inline). mass = 2.9t.

Of course, it needs to launch separately to the main lunar descent vehicle stack, shown here fitting sideways into a F9 re-usable, assuming it docks in LEO as part of Artemis 3.   

 

 

Edited November 20, 2019 by jinnantonix

[sevenperforce]

1 hour ago, jinnantonix said:

How about this?  Exactly the same model as being developed, but replace the Orion pressure vessel with a 3.3m diameter Lochheed Martin -type lander can. 

The model is two Mk1 lander cans, clipped into a scaled up structural tube, add top and bottom docking ports, ladder (need a longer one), and R-4D thrusters (4 x directional and 8 x inline). mass = 2.9t.

Of course, it needs to launch separately to the main lunar descent vehicle stack, shown here fitting sideways into a F9 re-usable, assuming it docks in LEO as part of Artemis 3.   

 

That's a good start...but I want to try to make the lower module launch vertical and mate horizontal too.

[tater]

My hope for Artemis is that all the CLPS landers work out for them.

[jinnantonix]

On 11/18/2019 at 1:01 PM, sevenperforce said:

That's a good start...but I want to try to make the lower module launch vertical and mate horizontal too.

I have had a go at modelling this, and while it can be done, it is not an improvement on the inline design.  The biggest problem is in modelling the docking procedures.  The craft requires additional avionics and directional thrusters for the docking maneouvres, whereas the inline design can utilise the existing equipment on the FHe second stage or the Cygnus resupply module.

I have made some improvements to the inline design, making the craft shorter and widening the lander leg base for stability.

 

Edited November 21, 2019 by jinnantonix

[jadebenn]

NASA wants to start procurement of an unpressurized lunar rover for the Artemis program.

NASA to seek ideas for an Artemis lunar rover

Quote

Speaking at the SpaceCom Expo here Nov. 20, Tom Cremins, NASA associate administrator for strategy and plans, said the agency will soon release a request for information for an unpressurized lunar rover for use by astronauts on Artemis lunar landing missions.

“We want that [rover] there when the first crews arrive and then be there subsequently to be able to be used potentially autonomously from the Gateway, to conduct operations and to add to the science objectives,” he said.

That RFI, which he said would be released “in the coming weeks,” would propose to eventually develop the rover through a public-private partnership. The work will be led by the Johnson Space Center.

My reaction can be summed up in two words: Heck yeah!

While a pressurized Lunar rover remains the holy grail of Lunar surface exploration vehicles, the capabilities an unpressurized rover provides are still nothing to sneeze at. It was such a game-changer on the late Apollo missions, and it still remains a huge shame it wasn't part of the earlier missions.

Edited November 21, 2019 by jadebenn

[mikegarrison]

4 hours ago, jadebenn said:

The capabilities an unpressurized rover provides are still nothing to sneeze at. It was such a game-changer on the late Apollo missions, and it still remains a huge shame it wasn't part of the earlier missions.

With any rover you still have the same issue ... you can't get too far from the ascent vehicle. If you are too far to walk back, then a rover failure becomes a single point crew-death failure. (This is, by the way, an issue I have faced right here on Earth. It's risky to go out snowmobiling by yourself, because it's way, way too easy to get out in the snow far too far to walk back.)

Edited November 21, 2019 by mikegarrison

[kerbiloid]

Spoiler

2 hours ago, jadebenn said:

NASA wants to start procurement of an unpressurized lunar rover for the Artemis program.

Don't they have youtube in NASA to just have a look at KSP rovers?
What else could be ever added?

Spoiler

Say, this one.

 

 

Edited November 21, 2019 by kerbiloid

[sevenperforce]

19 hours ago, jinnantonix said:

I have had a go at modelling this, and while it can be done, it is not an improvement on the inline design.  The biggest problem is in modelling the docking procedures.  The craft requires additional avionics and directional thrusters for the docking maneouvres, whereas the inline design can utilise the existing equipment on the FHe second stage or the Cygnus resupply module.

I have made some improvements to the inline design, making the craft shorter and widening the lander leg base for stability.

I like the increased stability.

Multidirectional thrusters on the lower stage are necessary, I believe, for the purposes of docking at LOP-G. Docking while connected to FHe upper stage is a non-starter; NASA would not entertain having an upper stage, even a safed one, meaningfully close to LOP-G. I think we can obtain much better performance and more downmass if we skip the Cygnus resupply module.

[jinnantonix]

4 hours ago, sevenperforce said:

Multidirectional thrusters on the lower stage are necessary, I believe, for the purposes of docking at LOP-G. Docking while connected to FHe upper stage is a non-starter; NASA would not entertain having an upper stage, even a safed one, meaningfully close to LOP-G. I think we can obtain much better performance and more downmass if we skip the Cygnus resupply module.

The LHe second stage directional thrusters are only used for remote controlled docking in LEO prior to TLI.  The LHe second stage is decoupled near LOP-G.  At LOP-G the lander refuelling vehicle docking is completed by using directional thrusters on the Cygnus. 

I don't think skipping the Cygnus is an option.  In the Integrated Exploration Manifest, logistics resupply appears in NASA's basic plan for every Artemis mission.  Food, water, oxygen and instruments, spares, etc. for a remote space station and lunar landing are needed for 4 crew over 3 weeks in space.  Also Cygnus is also the only mechanism I can see to dispose of the LLO-NRHO stage hypergolic fuel tank after the lander capsule/habitat docking at LOP-G.

 

Edited November 21, 2019 by jinnantonix

[sevenperforce]

34 minutes ago, jinnantonix said:

At LOP-G the lander refuelling vehicle docking is completed by using directional thrusters on the Cygnus. I don't think skipping the Cygnus is an option.  In the Integrated Exploration Manifest, logistics resupply appears in NASA's basic plan for every Artemis mission.  Food, water, oxygen and instruments, spares, etc. for a remote space station and lunar landing are needed for 4 crew over 3 weeks in space.  Also Cygnus is also the only mechanism I can see to dispose of the LLO-NRHO stage hypergolic fuel tank after the lander capsule/habitat docking at LOP-G.

Resupply is definitely necessary, and it would be great to be able to do each lunar sortie and resupply with a single TLI, but provisions for sending Cygnus resupply to TLI independently is fine too. How much dV does Cygnus have? I assume it's more than enough to get from TLI to LOP-G.

I'm confused about the hypergolic propellant tank. If it is only there to transfer propellant into the onboard tanks of the capsule, then why not drop it when you drop the ascent module? For that matter, just do the propellant transfer directly from the ascent tank...or even directly from the drop tanks.

[jinnantonix]

4 hours ago, sevenperforce said:

Resupply is definitely necessary, and it would be great to be able to do each lunar sortie and resupply with a single TLI, but provisions for sending Cygnus resupply to TLI independently is fine too. How much dV does Cygnus have? I assume it's more than enough to get from TLI to LOP-G.

I'm confused about the hypergolic propellant tank. If it is only there to transfer propellant into the onboard tanks of the capsule, then why not drop it when you drop the ascent module? For that matter, just do the propellant transfer directly from the ascent tank...or even directly from the drop tanks.

The Cygnus has limited dV but does not need it here, as it relies on the Orion SM or LHe second stage to provide the NRHO insertion.  The Cygnus also has a painfully low thrust, and is really only suitable for orbital rendezvous and burn to suborbital path (disposal).

The lander capsule/habitat can needs to be very light, ideally it does not need a permanent propellent tank for the fuel needed to go from LLO to NRHO. But yes, it is an option to just pump enough fuel into the capsule, and drop the last tank just prior to circularising in LLO.  I just figured if the Cygnus needs to de-orbit, then why not take an empty tank too, and lighten the capsule/habitat can.

 

 

[tater]

Here's a rover (needs different tires, obviously):

[kerbiloid]

2 hours ago, tater said:

Here's a rover (needs different tires, obviously):

Flat surfaces need greater thickness.

[sevenperforce]

19 hours ago, jinnantonix said:

The lander capsule/habitat can needs to be very light, ideally it does not need a permanent propellent tank for the fuel needed to go from LLO to NRHO. But yes, it is an option to just pump enough fuel into the capsule, and drop the last tank just prior to circularising in LLO.  I just figured if the Cygnus needs to de-orbit, then why not take an empty tank too, and lighten the capsule/habitat can.

That was my point, originally. I was initially saying we should have the capsule with no onboard propellant tanks and feed it during transit from an external drop tank. That requires development of a high-flow bipropellant coupling but does not require the development of micro-g propellant and pressurant transfer.

If we are putting tanks in the capsule and transferring in propellant and pressurant, then it will return to LOP-G with nearly dry tanks and nothing that needs disposal.

[jinnantonix]

1 minute ago, sevenperforce said:

That was my point, originally.

Yes, and you convinced me that lightweight habitat can and disposal of the last drop tank on a Cygnus was the right solution.  But as a I say, both options should work, and have pros and cons.

[jinnantonix]

On 11/22/2019 at 6:19 PM, kerbiloid said:

Flat surfaces need greater thickness.

[jinnantonix]

Not sure if anyone is subscribing to Apple TV, but the series For All Mankind is a very interesting show for space buffs.  In particular with regard to the Artemis Program, Episode 5 Into The Abyss includes a landing on the rim of Shackleton Crater.

Spoiler Alert

Spoiler

https://www.vulture.com/2019/11/for-all-mankind-recap-season-1-episode-5-into-the-abyss.html

Spoiler Alert!  The landing on the crater rim is unsuccessful in discovering water ice in the sunlit area of the rim, which in my opinion is not surprising.  However the intrepid crew abseils several hundred meters down the craters near vertical rim wall, and find water ice in a depression in the wall.  Personally I find this unlikely, as I see no reason why cometary material (the most likely source of water ice on the moon) would lodge in the crater wall.  I think the more likely site for finding water would be on the crater floor, and arising from comet impacts within the crater area, and falling to the floor.  There is no mention nor discussion of landing on the crater floor, nor any revelation about how future missions would successfully mine water from a sheer crater wall.   

More discussion here

Edited December 3, 2019 by jinnantonix

[tater]

The recent update by @jadebenn in the SLS thread got me thinking about the entire SYSTEM that SLS/Orion is, and how bad it is (again). Certainly in how it has been discussed by NASA (Gateway, etc).

The goal is for it is supposedly human BLEO, and the only destination in the realistic future that is BLEO is the lunar surface (we're no where near TRLs for Mars).

OK, so the only possible SLS mission is the Moon, fine. Since SLS cannot do the Moon in one launch, ANY architecture is distributed launch. It COULD do the Moon, if Orion was dumped in favor of a direct copy of Apollo for the CSM and LM (assuming the 45t to TLI is accurate). So that's a counterfactual to play with, cancel Orion, start over with a new capsule, then SLS becomes a Moon rocket that can actually do Moon missions. I'll leave that as an exercise for the reader.

Another idea is the Boeing concept of 2X SLS launches, presumably meeting at high lunar orbit. This is incredibly expensive even at the "no-way-it's-true" $800M/launch number (note that that is just the booster cost, Orion is a billion itself, and any lander will be similar (or more)). Using more realistic numbers of marginal cost makes it worse, and using the next best number, total post dev cost including program costs divided by launches its amazingly expensive, and using the best number by far---total program cost including dev over launches it's so astonishingly expensive to be silly to consider.

The current other Artemis scheme is also LOR, but at Gateway. This is distributed launch with commercial LVs doing most of the work. For some reason LOR is not a problem to some people on this forum, but EOR is deeply troubling. For reasons.

If you did EOR, but did NOT use SLS for Orion (but do use it for the lander), then you dock Orion to the SLS stack with the lander such that the total mass is 45t, and off to TLI. That means a 19t lander, where the lander does much of the LOI burn. Orion can get home from LLO, but cannot do LOI, and still come home. In this case, perhaps there are two LOI burns. One with the lander, and another with some of the Orion CSM props. That might be an architecture to mess with. This results in a sortie lander, clearly, since we're dealing with a LM clone but with more descent props (because LOI burn). If added surface capability is desired, send that ahead. The lander is a LANDER. A taxi. Crew egresses vehicle, then does the mission from a hab that is deployed ahead of time. They board the lander again to leave. Yeah, this is more launches, but the difference here is that while the landers are still used once, the HAB is reused. If you want another giant, expensive SLS launch, once again, use cargo, and design a 45t lander that is the hab. No ascent stage. What is the total dv for LOI/landing? 3100m/s? Looks like you could land 17 of those 45t on the surface. That's a decent sized hab.

Dunno, this seems more sustainable to me. Use minimalist landers, and send the max habitat possible.

Edited December 11, 2019 by tater

[tater]

Note also that while SLS Block 1 will be crew rated, there would be no requirement to crew rate any upgrades to SLS at all in the EOR case. EUS would still need to be, obviously (it's attached to Orion for TLI), but it might have a different standard since it would already be in space (catastrophic failures still being a concern, but LOM failures would simply result in Orion coming home). Any new boosters (BOLE) would not need crew rating, and new RS-25s would not need to be, either.

[jinnantonix]

8 hours ago, tater said:

The goal is for it is supposedly human BLEO, and the only destination in the realistic future that is BLEO is the lunar surface (we're no where near TRLs for Mars).

The advantage of NRHO is that it is a small delta-V from heliocentric orbit.  This makes it the ideal staging post for missions to asteroids, comets, as well as Mars, Venus and other planetary destinations.  
 

Quote

OK, so the only possible SLS mission is the Moon, fine. Since SLS cannot do the Moon in one launch, ANY architecture is distributed launch. It COULD do the Moon, if Orion was dumped in favor of a direct copy of Apollo for the CSM and LM (assuming the 45t to TLI is accurate). So that's a counterfactual to play with, cancel Orion, start over with a new capsule, then SLS becomes a Moon rocket that can actually do Moon missions. I'll leave that as an exercise for the reader.

If the Moon were the only destination then that would make sense.  But the moon is being considered more as a stepping stone, and in particular a place that may be able to provide fuel.   An Apollo style craft would get us to the moon, sure.  But what next?

Quote

The current other Artemis scheme is also LOR, but at Gateway. This is distributed launch with commercial LVs doing most of the work. For some reason LOR is not a problem to some people on this forum, but EOR is deeply troubling. For reasons.If you did EOR, but did NOT use SLS for Orion (but do use it for the lander), then you dock Orion to the SLS stack with the lander such that the total mass is 45t, and off to TLI. That means a 19t lander, where the lander does much of the LOI burn. Orion can get home from LLO, but cannot do LOI, and still come home. In this case, perhaps there are two LOI burns. One with the lander, and another with some of the Orion CSM props. That might be an architecture to mess with.

Agreed. Way too expensive.  This thread has presented many strong arguments that there are workable designs that can achieve the goal at much lower cost.

Quote

If you did EOR, but did NOT use SLS for Orion (but do use it for the lander), then you dock Orion to the SLS stack with the lander such that the total mass is 45t, and off to TLI. That means a 19t lander, where the lander does much of the LOI burn. Orion can get home from LLO, but cannot do LOI, and still come home. In this case, perhaps there are two LOI burns. One with the lander, and another with some of the Orion CSM props. That might be an architecture to mess with. 

A 19t lander would struggle to push the Orion to LLO, and then complete the landing and ascent.  Would like to see your design.

Quote

The lander is a LANDER. A taxi. Crew egresses vehicle, then does the mission from a hab that is deployed ahead of time. They board the lander again to leave. Yeah, this is more launches, but the difference here is that while the landers are still used once, the HAB is reused. 

  This means that the ideal lunar landing site must be found first, and then all subsequent landing is at that site.  This is a very inflexible plan.  Artemis is designed so that the landers can access multiple sites, and choose nearly any location on the moon's surface.

 

[tater]

43 minutes ago, jinnantonix said:

The advantage of NRHO is that it is a small delta-V from heliocentric orbit.  This makes it the ideal staging post for missions to asteroids, comets, as well as Mars, Venus and other planetary destinations. 

There is no possible reason for HUMAN missions anywhere short of Mars in that list.

There's no such thing as a "staging post," either. The propellants need to be dragged up there any dv savings from there is obviated by the need to drag it up there 10t at a time.

 

Quote

If the Moon were the only destination then that would make sense.  But the moon is being considered more as a stepping stone, and in particular a place that may be able to provide fuel.   An Apollo style craft would get us to the moon, sure.  But what next?

If the goal is to use the Moon/NRHO as some stepping stone, SLS is the wrong tool, it's far, far too small, and too expensive to be useful. Any such architecture is distributed, and as soon as you distribute launches, all that matters is cost. SLS fails epically at cost.

I personally don't think lunar props close, economically, except for offsetting landing costs. Maybe I'm wrong. Short of lunar propellants to NRHO, it's no stepping stone at all, it's not worth it to drag props to NRHO, and it's not worth sending people to asteroids/comets at all.

 

Quote

Agreed. Way too expensive.  This thread has presented many strong arguments that there are workable designs that can achieve the goal at much lower cost.

Yeah, I agree that alternate schemes might work, but "Artemis" is tied to SLS.

Quote

A 19t lander would struggle to push the Orion to LLO, and then complete the landing and ascent.  Would like to see your design.

I don't have one. It's way too tight, actually. Looks like I'm about 400-500 m/s short (even splitting the LOI burn with Orion doing what it can while maintaining dv for TEI). That's assuming a LM clone, so all hypergolic. If we could use methlox, I think it might actually work. With ZBO and hydrogen? Works.

 

Quote

  This means that the ideal lunar landing site must be found first, and then all subsequent landing is at that site.  This is a very inflexible plan.  Artemis is designed so that the landers can access multiple sites, and choose nearly any location on the moon's surface.

You don't send people for that, that's what robots are for. Every single human launch will take---even magically eliminating SLS, which won't happen---a billion dollar Orion capsule (plus whatever the SM costs, lol). Assuming the capsule flies on SLS alone, how many robots could be sent for 4.5 billion a year (the cost of a single SLS flight with Orion on top, not counting the ESA contribution of the SM at all)?

Edited December 12, 2019 by tater