NASA HLS (Human Landing System) Lunar Landers

[Steven Pietrobon]

Article by Anatoly Zak for Popular Mechanics on NASA's Lunar lander plans. Article says the lander mass is 45 t (three times that of Apollo) and is split into three 15 t parts: Ascent Stage, Descent Stage and Space Tug. Space Tug takes the stack from the Gateway to LLO where the Space Tug separates. Descent stage goes from LLO to surface. Ascent Stage (with Cabin) leaves Descent Stage behind and goes into LLO. Not sure if the Space Tug is then used to take the Ascent Stage to the Gateway, or if they go their separate ways. The article says that a 22 t tanker is used to refuel the Ascent Stage and Space Tug at the Gateway. That means each new launch requires 22+15 = 37 t of payload to be sent to the Gateway, requiring a dry mass of about 7 t (19%). Alternatively, we can send a 20 t two stage expendable lander directly into LLO which has a dry mass of 5 t (25%) and ditch the Gateway. I know which scheme I would go for! :-)

NASA’s Return to the Moon Could Include a Reusable Lunar Lander

A reusable lander could make the proposed lunar station a more promising idea.

https://www.popularmechanics.com/space/moon-mars/a24115130/nasa-reusable-lander/

[ncb1397]

It seems like an updated lunar module could do the job. Wikipedia lists the Ascent stage as capable of 2220 m/s and the descent stage as capable of 2500 m/s. Of course, this isn't counting the rocks, rover, cameras, film, astronauts, etc. I think we are past the sortie phase though and we are definitely past film and so the requirements may be different. This just has to get them up and down to their equipment pre-placed on the surface. Sample collection can be done with robotic spacecraft. Doing the numbers myself doesn't exactly recreate that, but it is pretty close. That is basically what is required for NRHO to the surface and back give or take.

I think a 15 t+ ascent stage is too big, and that cascades to come up with the 45 t mass. Probably better to keep it at the 30 t at gateway mass so future LVs can lift it all at once (as a precursor to all the fancy in orbit refueling and assembly). A 10 t stage can easily dock that to the gateway after TLI injection leading to a TLI mass of 40 t (maybe a little less). That can be thrown all at once with next generation SHLVs.

But my preferred phase split is sort of opposite what is outlined here, instead of the descent stage being two stages with a space tug, the ascent stage should be two stages. The split is then the following

TLI to NRHO and descent: 3000 m/s
ascent to LLO: 1800 m/s
LLO to NRHO: 900 m/s

This allows enough delta-v on lunar launch that, depending on where it is, it can separate from a malfunctioning ascent stage and either reach LLO or reach the surface again. The only phase of flight that doesn't have a backup is then LLO to NRHO, but you aren't going to hit the surface immediately after shutting everything down so it gives enough time for a rescue (probably the next lander docked at the DSG).
 

[Zed_Noir]

The Popular Mechanics article didn't stated what kind of propellants will be used. I am presuming will be likely HydroLox with less likely choice of MethoLox. The type of propellants selected dictates the size of the vehicle.

[Zed_Noir]

It seems like an updated lunar module could do the job. Wikipedia lists the Ascent stage as capable of 2220 m/s and the descent stage as capable of 2500 m/s.
<snip>

However the Apollo LEM uses Aerozine 50 which is a relatively dense hyperolic propellant that reduces the vehicle size along with higher motor ISP.

It is unlikely that there will be further future usage of Aerozine 50 by anyone after the last Delta II launch. It is a terribly toxic and corrosive substance.

[speedevil]

The Popular Mechanics article didn't stated what kind of propellants will be used. I am presuming will be likely HydroLox with less likely choice of MethoLox. The type of propellants selected dictates the size of the vehicle.

Three stages really make the rocket equation bite a lot less hard.
5km/s with the proposed 60 ton behemoth SSTO hydrolox lander, with 20 tons payload, naively methalox makes it 70 tons, and hypergolics 130 tons.
But, obviously, if you throw away half of the mass of the vehicle on the surface, hypergolics are back more-or-less where you started, and methalox may be considerably better.
(hydrogen is more complex)

[Propylox]

Article by Anatoly Zak for Popular Mechanics on NASA's Lunar lander plans. Article says the lander mass is 45 t (three times that of Apollo) and is split into three 15 t parts: Ascent Stage, Descent Stage and Space Tug. ..The article says that a 22 t tanker is used to refuel the Ascent Stage and Space Tug at the Gateway. ..

That doesn't make a lot of sense. Can I get a consensus on implied masses?
Descent Stage: 1mt structure + 14mt propellant
Ascent Stage: 3mt structure + 7mt propellant
Space Tug: 5mt structure + 15mt propellant

[M129K]

The article states the following:

As a result, the expendable descent stage, which would arrive with each new Orion crew (as well as propellant for the ascent engine), could have a minimum size, while the space tug could be used for multiple ferry trips.

It seems to imply that the space tug could perform multiple missions before needing to refuelled, so all that would be needed for an individual lunar sortie is a single launch of Orion+propellant+descent stage. Still, that would be something on the order of 45+ tons to TLI, so definitely too heavy for a single Block 1B SLS. Is this supposed to be a two-launch per sortie affair, in which every mission requires one 22 ton tanker and one Orion+descent stage launch?

[TrevorMonty]

Why not go straight to single stage reuseable lander? DV required is 5kms for round trip.
A 10t 360isp Methane lander needs 32t fuel. Can be LOX fuelled with ISRU, lighter methsne coming from earth.
 A 10t 460isp Hydrogen lander needs 21t fuel. Can be fully fuelled with ISRU

[M129K]

Lockheed Martin's 62 ton lunar lander can only land 1 ton of payload to the lunar surface, versus the ~15 tons of this notional design. If you don't have a separate descent stage actually building the kind of base you need to enable large scale ISRU is very difficult.

[jongoff]

Lockheed Martin's 62 ton lunar lander can only land 1 ton of payload to the lunar surface, versus the ~15 tons of this notional design. If you don't have a separate descent stage actually building the kind of base you need to enable large scale ISRU is very difficult.

That was 1 ton of payload in addition to a crew cabin. A cargo-only version would have a lot more payload. And if you based your depot in a high polar LLO like you ought to for surface ops, you could probably get north of 15tons of delivered payload out of a lander that size. Possibly closer to 20-30mT. I'd have to run some numbers.

~Jon

[jongoff]

Lockheed Martin's 62 ton lunar lander can only land 1 ton of payload to the lunar surface, versus the ~15 tons of this notional design. If you don't have a separate descent stage actually building the kind of base you need to enable large scale ISRU is very difficult.

That was 1 ton of payload in addition to a crew cabin. A cargo-only version would have a lot more payload. And if you based your depot in a high polar LLO like you ought to for surface ops, you could probably get north of 15tons of delivered payload out of a lander that size. Possibly closer to 20-30mT. I'd have to run some numbers.

~Jon

Yeah, if you assume the crew cabin is ~10mT of the 22mT dry mass for the LM lander (ie that the lander propulsion section is ~12mT), I get a payload drop-off capability of ~39mT using base your system in LLO. I still get 12mT of drop-off capability if you base your system out of NRHO. This is part of why I think NRHO sucks as a staging point for lunar lander missions--adding another 40% to the round-trip dV is silly.

~Jon

[M129K]

That was 1 ton of payload in addition to a crew cabin. A cargo-only version would have a lot more payload. And if you based your depot in a high polar LLO like you ought to for surface ops, you could probably get north of 15tons of delivered payload out of a lander that size. Possibly closer to 20-30mT. I'd have to run some numbers.

~Jon

The 1 ton payload is also in addition to sufficient propellant to fly back to EML2. If we turn Lockheed's lander into a cargo lander with 39 tons of payload, we just turned it into a bigger version of NASA's notional expendable descent stage; a ~90 ton behemoth of an expendable descent stage you'd have to get into LLO, somehow. Not a reasonable scenario without some very big propellant plants already on the moon.

[Oli]

Lockheed Martin's 62 ton lunar lander can only land 1 ton of payload to the lunar surface, versus the ~15 tons of this notional design. If you don't have a separate descent stage actually building the kind of base you need to enable large scale ISRU is very difficult.

That was 1 ton of payload in addition to a crew cabin. A cargo-only version would have a lot more payload. And if you based your depot in a high polar LLO like you ought to for surface ops, you could probably get north of 15tons of delivered payload out of a lander that size. Possibly closer to 20-30mT. I'd have to run some numbers.

~Jon

Yeah, if you assume the crew cabin is ~10mT of the 22mT dry mass for the LM lander (ie that the lander propulsion section is ~12mT), I get a payload drop-off capability of ~39mT using base your system in LLO. I still get 12mT of drop-off capability if you base your system out of NRHO. This is part of why I think NRHO sucks as a staging point for lunar lander missions--adding another 40% to the round-trip dV is silly.

~Jon

I think there are other factors to consider. The table below is from here.

[A_M_Swallow]

If cargo landers are to be based at the Gateway spacestation it will need attachment points. The standard NASA Docking Port is too sophisticated since it has a hatch for people access. A mechanical connector, electrical power, data and control interfaces may be sufficient, providing cargo and the various propellants can be loaded using the station's arm.

[ncb1397]

If cargo landers are to be based at the Gateway spacestation it will need attachment points. The standard NASA Docking Port is too sophisticated since it has a hatch for people access. A mechanical connector, electrical power, data and control interfaces may be sufficient, providing cargo and the various propellants can be loaded using the station's arm.

There will be an station arm, so there will be at least a couple grapple fixtures with power/data. The lander just has to replicate the end effector. Even modules that didn't have them installed had them installed later, like the fixture on the Zarya module.

[A_M_Swallow]

If cargo landers are to be based at the Gateway spacestation it will need attachment points. The standard NASA Docking Port is too sophisticated since it has a hatch for people access. A mechanical connector, electrical power, data and control interfaces may be sufficient, providing cargo and the various propellants can be loaded using the station's arm.

There will be an station arm, so there will be at least a couple grapple fixtures with power/data. The lander just has to replicate the end effector. Even modules that didn't have them installed had them installed later, like the fixture on the Zarya module.

The station's arm can hold cargo landers for a few hours but since between missions landers may be parked for many weeks the arm will be needed for other activities. Commonality amongst grapple fixtures, end effectors and landers is a good idea.

[Nibb31]

Hubble and JWST have been fitted with passive  IDS compatible docking fixtures that only provide a mechanical attachment. I don't see why you couldn't use that.

[A_M_Swallow]

Hubble and JWST have been fitted with passive  IDS compatible docking fixtures that only provide a mechanical attachment. I don't see why you couldn't use that.

Size and weight. The IDS docking port is designed to have a Dragon or CST-100 massing 10-30 tonne attached to the other end of it. The Moon Express MX-1 lunar lander only masses 250 kg (0.25 tonne) when fully fuelled.

[TrevorMonty]

Hubble and JWST have been fitted with passive  IDS compatible docking fixtures that only provide a mechanical attachment. I don't see why you couldn't use that.

Size and weight. The IDS docking port is designed to have a Dragon or CST-100 massing 10-30 tonne attached to the other end of it. The Moon Express MX-1 lunar lander only masses 250 kg (0.25 tonne) when fully fuelled.

From Gateway MX-1 should be able to do round trip to surface and back while returning sample. Could get ride to Gateway in Dragon trunk or attached to Cygnus some how.

[speedevil]

<snip of NHRO being a bad orbit>

I think there are other factors to consider. The table below is from here.

This table bakes in a lot of assumptions, which are not obviously true if your budget is $50B.
To take the most obvious point 'communications' can be fixed by a more-or-less standard commercial GEO sat at L2.

Stationkeeping at 300m/s/year being 'red' is basically an implicit assumption of launch costs.
(that it would be a nontrivial part of a $5B/year to get ~1 ton of hypergols or 200kg of xenon to LOPG).

The above lander would be quite capable of shuttling between LLO and GTO, for example, taking on some 20 tons of cargo in GTO from commercial launches and delivering as stationkeeping propellant.

The table also bakes in an unmodified Orion with no operational changes (stationkeeping on a 10m foil balloon in LLO eliminates the thermal issue, as a silly example).

LLO does complicate power and thermal obviously.

But the table is very, very particular to the design of LOPG, for obvious reasons.