NASA HLS (Human Landing System) Lunar Landers

[Joseph Peterson]

Now back to the Lunar lander we are supposed to be discussing.

My understanding is the descent stage is left on the Moon.  One of the missions this lander could be tasked with is delivering hardware to an ISRU hydrolox plant.  If we can sufficiently protect the descent stage during the ascent stage's launch, descent stages could be repurposed as ISRU hardware.

I posit that commonality between the three stages' propulsion systems is highly desirable.  Commonality means only one set of spare parts is needed, saving valuable mass for other purposes.  Descent stage engines that survive can be used by repair facilities  on the surface.  Alternatively they could be returned to orbit.  

If we are going to go to the Moon to build a hydrolox plant, this looks like a plausible option for delivering the plant.  Working on the assumption that the tanks can store useful things that aren't hydrolox, there should also be a potential market at any other type of permanent facility.  Who knows, perhaps spent descent stages could one day make decent fish tanks.  

I don't like this concept for sites which aren't planned for permanent outposts.  My preference is to limit the amount of payed for launch mass we leave as trash.  Ideally this concept should be cheap enough so that it can be paired with a fully reusable lander.  As I prefer staging in LLO, I would prefer to see the tug repurposed as a LEO/LLO fast transport.  Staging in LLO also allows hydrazine or better chemical propellants to be used.  

I see a proposal that has the potential to survive an architecture change.  There is a possibility for reuse or repurposing all major components.  The usual suspects have the capability to develop the hardware.  As part of a larger effort to bring hydrolox propellant depots to TRL-9, something big needs to retire, and Marshall is the center that I expect would get the bulk of the work.  There is a lot to like here.

Edit: Moved the comment to start the new page correctly.

[A_M_Swallow]

An alternative to throwing away the entire decent stage for each landing is to use drop tanks. This allows reuse of the engines and avionics such as radars.

[MATTBLAK]

Perhaps whatever are the larger tanks - fuel or oxidiser - can be dropped whilst the others remain integral to the stage.

[Oli]

Regardless of Orion's capabilities, isn't the total delta-v from TLI to the surface and back the relevant figure? LLO saves you roughly 500m/s compared to NRO, which isn't much.

It's 730-900 m/s from NRHO to LLO.  Call it 800 m/s.

If it's, say 2000 m/s between LLO and the surface.  Then a fully reusable LLO-based lander needs a delta-V or 4000 m/s, whereas an NRHO-based one needs 5600 m/s.  If Isp is 350 s, then the respective mass fractions are 0.31 and 0.20.  That's a pretty significant difference.

True, though it assumes a fully resuable lander without ISRU or in-space tug from NRO to LLO.

[ncb1397]

Now back to the Lunar lander we are supposed to be discussing.

My understanding is the descent stage is left on the Moon.  One of the missions this lander could be tasked with is delivering hardware to an ISRU hydrolox plant.  If we can sufficiently protect the descent stage during the ascent stage's launch, descent stages could be repurposed as ISRU hardware.

Presumably a "base" could accommodate a launch mount and ascent stages could be moved over so as not to damage descent stages.

[Joseph Peterson]

Now back to the Lunar lander we are supposed to be discussing.

My understanding is the descent stage is left on the Moon.  One of the missions this lander could be tasked with is delivering hardware to an ISRU hydrolox plant.  If we can sufficiently protect the descent stage during the ascent stage's launch, descent stages could be repurposed as ISRU hardware.

Presumably a "base" could accommodate a launch mount and ascent stages could be moved over so as not to damage descent stages.

Another good option to consider.  Have you given any thought to how early into base construction this becomes feasible?

[GWH]

So how do you get to LLO with Orion?

Make EUS last the three days to the Moon and have EUS put Orion into LLO. Orion then has enough delta-V to perform TEI.

And then there was the old ULA paper that replaced the propulsive element of Orion's service module with an ACES stage.
https://www.nasaspaceflight.com/2009/09/ula-claim-gap-reducing-solution-via-eelv-exploration-master-plan/

[A_M_Swallow]

Now back to the Lunar lander we are supposed to be discussing.

My understanding is the descent stage is left on the Moon.  One of the missions this lander could be tasked with is delivering hardware to an ISRU hydrolox plant.  If we can sufficiently protect the descent stage during the ascent stage's launch, descent stages could be repurposed as ISRU hardware.

Presumably a "base" could accommodate a launch mount and ascent stages could be moved over so as not to damage descent stages.

Another good option to consider.  Have you given any thought to how early into base construction this becomes feasible?

A launch mount will have to be brought from Earth, so any time after we have a sufficiently large lander. What is the approximate mass of a launch mount?

The first generation of lander have payloads of up to 100 kg. A second generation flying in 8 or 9 years time have payloads in the 5 tonne range.

Until there are people on the Moon base construction has to use self assembling items or possibly a small robot.

[Nibb31]

Why not use the old Soviet LK architecture? A single set of (redundant) engines that are used for descent and ascent, with internal tanks for ascent, and an expendable frame holding the landing legs and the descent tanks (as well as any one-way unpressurized cargo).

Back in orbit, you just need to refit new descent tanks/legs for the next mission and refuel the accent tanks.

I think that drop tanks are probably better than expending a whole stage.

[Markstark]

Gerst briefed this chart today at NAC today

[A_M_Swallow]

Gerst briefed this chart today at NAC today

If the Descent Element is used as a cargo lander without an Ascent Element then it will need its own navigation system and radar. A cost and mass increase.

[Markstark]

There are always trade-offs. I’m just glad reusability is being considered for at least part of this architecture.

[speedevil]

Gerst briefed this chart today at NAC today

If the Descent Element is used as a cargo lander without an Ascent Element then it will need its own navigation system and radar. A cost and mass increase.

GPS is marginally usable from the moon.
https://gsp.esa.int/documents/10192/46710/C4000107097ExS.pdf/0c0e0f30-b9b9-4afc-8fff-eaeb2e1eb616 - on weak GNSS.

It would be interesting to offer a $100K prize to develop a complete software based navigation system that is good to 0.2m or so, for a large target area.

The LRO imagery over the moon is startlingly good - much of the moon is imaged to 0.5m or better, and for one sun angle at least the terrain is basically completely designed for image recognition - unchanging and no atmosphere effects.
Sun angle makes it somewhat more complex.

[ncb1397]

Gerst briefed this chart today at NAC today

If the Descent Element is used as a cargo lander without an Ascent Element then it will need its own navigation system and radar. A cost and mass increase.

Perfect opportunity to plug a historical Apollo video:



So, was the landing radar put there because of the planned but never used lunar truck mode or is it simply the best place to put it to allow for lunar surface line of sight in both hoizontal and vertical orientations?

[Markstark]

Gerst briefed this chart today at NAC today

While briefing this chart, Gerst noted that the three piece architecture allows them to look at using other available rockets and not just SLS. He also hinted at the transfer element (tug use to get from Gateway to LLO) potentially being based on the European Service Module since it has the delta V required. The Ascent Module is sized to have a delta V capable of supporting an abort back to Gateway from any part of its mission profile. He noted that this delta V is similar to what’s required for a Mars Ascent Vehicle. Regarding the Descent module, he mentioned potentially having multiple commercial providers with their owns designs but are compatible with the Ascent Module design. Descent Module would also be used in a cargo configuration.

[A_M_Swallow]

So, was the landing radar put there because of the planned but never used lunar truck mode or is it simply the best place to put it to allow for lunar surface line of sight in both hoizontal and vertical orientations?

The whole of the LEM was expendable so no consideration was needed for a second landing. The landing radar was not used to help the Ascent Stage rendezvous and dock with the Command Module so there was probably no benefit from attaching the radar to the Ascent Stage. The propellant needed to lift the mass could be saved by fitting it to the Descent Stage.

NASA hopes to make the Ascent Stage of the new lander reusable, so by attaching the landing radar to the Ascent Stage it will not have to buy a new radar for each landing.

[A_M_Swallow]

GPS is marginally usable from the moon.
https://gsp.esa.int/documents/10192/46710/C4000107097ExS.pdf/0c0e0f30-b9b9-4afc-8fff-eaeb2e1eb616 - on weak GNSS.

It would be interesting to offer a $100K prize to develop a complete software based navigation system that is good to 0.2m or so, for a large target area.

The LRO imagery over the moon is startlingly good - much of the moon is imaged to 0.5m or better, and for one sun angle at least the terrain is basically completely designed for image recognition - unchanging and no atmosphere effects.
Sun angle makes it somewhat more complex.

I suspect that NASA is planning on using the CoOperative Blending of Autonomous Landing Technologies (COBALT) system.
https://mars.nasa.gov/news/1970/cobalt-flight-demonstrations-fuse-technologies-to-gain-precision-landing-results

[Steven Pietrobon]

For an Isp of 310 s, 2.85 km/s delta-V, and 9-12 t initial mass, the final mass ranges from 3.5 to 4.7 t. I have to seriously question that the development of three different elements for the lander (one or two of them expendable anyway) and all the elements of the Gateway is worth the cost of saving that relatively small mass.

[M129K]

So we're dealing with a mass of the habitable element on the order of ~4 metric tons and a total fuelled lander mass on the order of ~40 tons, assuming it uses hypergolic propellants.

Back in 2013, SpaceWorks did a small lander study, also assuming a payload mass of 4.0 metric tons to and from the moon with L2 as a staging point. A single stage lander fuelled by hypergolic propellants would have a mass of over 60 tons, which is far too heavy for commercial launchers and even SLS, but a single stage hydrolox lander with the same payload would have a mass of 41 tons, similar to the NASA lander, and would be fully reusable. Using hydrocarbons in a fully reusable two stage configuration would also result in a total mass of 37 tons for methane or 42 tons for kerosene, with no individual component being too heavy for commercial launchers.

http://www.sei.aero/archive/AIAA-2013-5479_Presentation.pdf

Using hypergolic propellants seems to force NASA to split the lander into multiple highly specific components, preventing full reuse and increases the risk of a LoM. The only real upside I can think of is that hypergolic propellants don't require the development of long term cryogenic propellant storage, new hydrocarbon engines and/or cryogenic on-orbit propellant transfer, technologies that we will need for an eventual mission to Mars anyway. This lander design seems like an overly specific, complicated technological dead end.

[Markstark]

The deck of charts are now publicly available here: https://www.nasa.gov/directorates/heo/nac-heoc

But these appear to be the most relevant to the current discussion (these are from Crusan’s slides)