jinnantonix

If the Blue Origin assumption about ascent vehicle wet mass = 6.5t is practical, then my calculations show that a simpler design can complete the missions with just the 3 launches, and still add a LOP-G component with each mission.

Total mission cost including launch costs. I can't see an architecture that includes a SLS Cargo launch will win - it is just too expensive. In my opinion, any lunar landing mission architecture that includes more than 2 x HLV commercial and 1 x SLS is going to fail, it simply won't get long-term funding approval.

My model has an integrated expendable stage at 27.5t wet mass, including AV and engine(s), DV and transit drop tanks, excluding the reusable crew taxi. From the above table, there is no LV second stage craft that can boost a craft this heavy to TLI, let alone to NRHO. The best option for TLI would appear to be a Falcon expendable second stage which can get the craft to about 75% of TLI. The Falcon Heavy expendable can launch 54t payload to LEO, so this would launch the lunar lander and adding drop tanks to the craft at launch to provide extra fuel to the complete the boost to TLI and then to insert into NRHO. So each Artemis mission would include a Falcon Heavy expendable launch for the lunar lander plus TLI/NRHO insertion drop tanks, a launch of a zero payload Falcon Heavy with expendable second stage which docks with the lunar lander in LEO, plus SLS/Orion with a co-manifested LOP-G component.

Simulation of the 6.5t AV completed My model assumes a smaller lighter Orion-type pressure vessel, the AV has a wet mass of 6.8t, slightly more than the BO assumption to accommodate three engines at AV lift off. The central engine is throttled down for hovering/landing, but assuming it can be throttled up to full in case of an outer engine failure. I still like the 3 inline design for redundancy for ascent vehicle lift off. Since 3 engines are required for descent anyway, it is a trade-off between mass and redundancy (I choose safety first). A single Shuttle OMS or a AJ10-190 as a central engine with two additional outer engines (could be SuperDRACOs or AJ10-190s). The re-usable AV (wet mass 2.7t) , with a transit attachment, a drop tank and single engine or multiple thrusters for insertion into NRHO and rendezvous with the LOP-G . I calculate the extra props, drop tank and engine adds 1.0t to the craft. This may be delivered to the LOP-G initially on a Falcon 9 or Vulcan. The DV + transit drop tanks stage has a wet mass of 27.5t at Earth launch, plus 5.0t additional drop tank for the deceleration and rendezvous at the LOP-G. It is assumed that this is launched to LEO on a Falcon Heavy, thence TLI from any one of the options that @sevenperforce has suggested. Note during NRHO insertion, the engine burns on the three inline engines can be interchanged between central and outer pair to reduce the total number of firings per engine. The craft tests like a dream, in particular the wide landing base reduces the risks around lateral movement at touchdown and landing on a slope.

Yes, that's what I was doing. Just couldn't eyeball the angles right with the powered deceleration. I thought of using the AJ10-118, but that's a beast of an engine, weight 450kg with a huge engine bell. The OMS engine at 29kN thrust would be a good choice and should have just enough thrust at lift-off. Still need to add two engines for the LLO to surface burn though.

Thanks for the link. When I did the station building simulation, I did the rendezvous many times, and without the use of a supercomputer to accurately calculate the optimum path, I was consuming about 800m/s. This is more like the mass of the AV I used in my simulation. I was thinking this was wrong (too light), but now you have confirmed that my original calcs were accurate. This definitely rules out using an Orion pressure vessel (too massive), but I reckon a smaller, lighter vessel could be constructed using the same proven methods, and use Orion's avionics and LS facilities. One issue I am facing with the ascent vehicle: at 6.5t wet mass, a single AJ10-180 at 11kN thrust does not get the AV off the lunar surface efficiently. I prefer the AJ10 Space Shuttle engine for it's proven reliability and throttling capability. My simulation utilised two AJ10-190 engines mounted each side of the AV capsule. This works from a TWR viewpoint, but would mean disaster if one of the engines failed during ascent. A single central SuperDRACO is fine for launching the AV, but as you say, cannot be throttled down to hover when landing the AV alone (after crashing the DV stage). The single SuperDRACO throttled down works fine when landing the DV and AV together, and the latter configuration, while less fuel efficient during landing, allows leaving behind the landing legs at AV launch. In order to transit from LLO to lunar surface three engines are needed ~100kN thrust. The two additional engines could be attached to the DV and left on the lunar surface. Alternatively three inline SuperDRACOs on the AV provides redundancy during the ascent phase.

When you mention building use the Canadarm, are you assuming using the existing facilities at ISS? The problem I see with this is the size of the second stage of the LV that is needed to launch the fully assembled lunar lander from LEO to TLI. There will also need to be a 800m/s burn from TLI to LOP-G rendezvous, and assume that there will be small prop drop tanks included so these can be jettisoned prior to LOP-G to LLO transit? These numbers seem very low. At lunar landing, the DV will still have some fuel in the mostly empty tanks, plus lander legs and decouplers. I calculate approx 3.2 tonnes for that, we agree on that. Then there is static payload (science equipment, rovers, etc) and 2 weeks of life support, what mass are we assuming here? How about the airlock? Is all this included in the 2.8 tonnes you mention above? My calculations are higher than yours. Assuming crew taxi is 4.0t AV dry mass including payload, LS etc, adding AV props and tank and DV components, I am getting 15.1t wet mass immediately prior to landing on the surface. One down-throttled SuperDRACO is fine for that. What am I missing here?

I never said it was easier or less risky around the moon. Nor do I think it is easier to do it in LEO. They both have challenges, and in my opinion equally difficult. However the whole idea of Artemis and LOP-G is to have a facility with comms, robotics, life support etc that can be used as a staging post, not just for lunar missions but also for deep space. No point in building it if you are not going to use it.

Assembly in LEO? Hmm, that seems a bit contrary to the LOP-G concept. I am more inclined to build the tanks a bit larger with extra fuel for the dV=800 and (same as the AV) use RCS thrusters to decelerate to rendezvous with the LOP-G. There is surely a way for the 3 stages to dock inline at the LOP-G. Utilising the Canadarm for the assembly (especially of of the final stage) is the only hurdle, but it is not insurmountable (pun intended). If Earth controlled docking using thrusters alone were feasible (and I am sure it is) then there are no constraints at all. I see from the Blue Origin announcement they are keen to go down the hydrolox path. Just can't see that as being feasible, hydrogen boil off and resulting constraints around cryogenics mass, as well as launch scheduling and mission logistics, etc...

True. I'll give this some thought, there must be a way to design this so the tanks can be launched fully fueled on a commercial LV (eg Falcon Heavy) and stacked by inline docking at the LOP-G. The problem is that each launch need to include an expendable transit vehicle to decelerate each component to rendezvous at the LOP-G, dV ~ 800m/s.

Tend to agree, but depending on the approved lunar lander design, I think it is feasible to send a crew to LOP-G and to land a robotically controlled prototype. The lander could crash, or not successfully return to LOP-G, but as long as Orion delivers the crew safely on the round trip, the Artemis 3 mission would be considered success. Artemis plans up to 5 landings to Artemis 8, and if there are a few uncrewed tests before the first footsteps on the moon, that still fits with the program objectives.

@tater I was responding to the discussion about 200 ton re-usable landers and ion engines, which has nothing to do with Artemis, and is something we would not see until well after the timeline for Artemis has expired. That is unless you believe that Electric Jesus is completing preparations for using Starship to take paying passengers to Mars and back. LockMart certainly thinks so, but with a bit of thought (which LockMart has not yet invested in), it might be possible to actually launch a lunar lander cost effectively with commercial LVs. The Artemis Program doesn't just achieve a crewed landing, it extends to multiple landings, and across the entire construction of the LOP-G and science gathering needed to deliver on Artemis 8 a "Lunar Surface Asset", which I take to mean an ISRU facility. There isn't much use in doing Artemis if there is no way to effectively lift the proceeds of all this effort from the lunar surface, to somewhere it might be used productively. Expect that as Artemis proceeds, assuming it proves ISRU feasible, there will be more requests for research into NTER craft and ISRU facility design and build, and no reason why this would not be contracted out to the private sector.

There is no intention in my mind of these craft being used to land humans on the lunar surface, at least not in the short term. If you look up the thread, I see the immediate requirement for a crewed lunar lander architecture being based around more familiar human rated systems, and in particular a fully expendable hypergolic fueled tug, and a re-usable variant of the Orion pressure vessel with hypergolic thruster engines. This provides the initial landing systems to prove lunar mining and ISRU. Once that is proved, the NTERs provide an automated service for cargo delivery, or perhaps deep space ferrying. Any future human landings on the moons surface would continue to use the already proven human rated systems, although likely the landers will be launched fully integrated and fueled into LLO by BFG or New Glenn cargo LVs and ferried to the LOP-G using an NTER tug.

I am sure having propellant tanks between the engines and humans should be enough protection. Can't see radiation from these engines being a significant hazard, compared to the risks and environmental hazards of being in deep space. Not sure why humans would be "walking around the engines", I would envisage everything to be autonomous, including the lunar mining operation.

My testing shows from a performance perspective NTER is quite capable of lunar descent and ascent. Ultimately a means of autonomously ferrying ore or fuel or propellant to LLO is needed, I just don't see the need for designing and building multiple ship propulsion systems, when a single NTER based system does it all at the best possible efficiency levels. A pair of tugs can ferry raw materials/propellant from the lunar mining facility to the LOP-G ESPRIT module, and another pair can be fueled at LOP-G ESPRIT module for Earth-Lunar transit operations, while in the longer term future another pair could be deployed to conduct deep space transit operations. Human rated vehicles like Orion or Dragon v2 would still be needed, not the least for Earth launch and re-entry. I would envisage another type of craft would be needed for human rated long term (beyond 3 weeks) deep space operations, that would incorporate spin gravity and radiation protection. This craft would be ferried by the NTER deep space tugs.

We can all see that commercial rockets like BFR and New Glenn will be launching big payloads to LEO with re-usable, natural gas powered rockets within a decade, and these will dramatically decrease the cost of payload to orbit. But how suitable are these craft for humans, or for deep space operations? How efficient are they for providing TLI or TMI where there is restricted re-usability due to the limitations of cryogenic fuels? In my opinion for operations beyond LEO we would best use NTER - Nuclear Thermal-Electric Rockets as tugs. These would be robotically controlled re-usable craft used to provide the dV to transit cargo from LEO to lunar orbit, as well as transporting to locations in heliocentric or Martian orbit. With ISP ~550-800, 2 years operation between nuclear refueling (at the ISS?) and enough thrust to launch from the lunar surface, these are the ideal compromise between time and efficiency. Ideally the craft would be refueled with mass propellant - hydrogen or methane for launch or (storeable) ammonia for long term missions, with the propellant manufactured on the lunar surface. Of course, this option all depends on the viability of fuel manufacture at the lunar south pole ... which is what Artemis is all about. We don't get to do any of this funky stuff if there is no raw material for fuels, or ISRU cannot be setup cost effectively.

Some details around manufacturing here: http://spaceflight101.com/spacecraft/orion/ "Installed around the pressure vessel and its various external systems are composite backshell panels with titanium honeycomb cores that provide primary thermal control to the spacecraft as well as micro-meteoroid orbital debris (MMOD) protection using laminate panels. A total of 49 composite panels make up Orion’s outer shell with additional thermal protection layers installed on top. A total of 970 TUFI coated AETB-8 thermal tiles with Space Shuttle heritage are installed on Orion’s backshell to protect the internal equipment from heating during re-entry. These tiles consist of silica glass fibers and have excellent thermal characteristics. The forward bay is protected by a dedicated cover also using composite materials (see section on Orion’s parachutes). In the aft section, Orion’s core structure interfaces with the Heat Shield Support Structure consisting of a titanium skeleton that holds the heat shield. To withstand re-entry heating of up to 2,800 degrees Celsius when returning from Mars, the Orion spacecraft is equipped with the world’s most powerful heat shield which also is the largest ever built with a diameter of just over five meters. The heat shield uses a titanium skeleton that provides the interface points with the crew module and adds strength to the heat shield required for it to withstand the impact with the water at splashdown. The skeleton is held in place by six brackets on the CM aft bulkhead. Fitted atop the skeleton is a carbon fiber skin that provides additional strength and acts as mounting surface for the AVCOAT ablative heat shield material. This structure consists of one center, 18 gore and 18 shoulder panels." Seems to me there is a lot of room for reducing the lander capsule mass by redesigning the outer shell minus the load bearing and heat resistant components. THere is no requirement for chutes nor any of the associated systems. Items like seats could be removed entirely, like Apollo the crew remain in an upright "standing" position during landing, ascent and craft acceleration. Some mass is added for the airlock and RTG and perhaps additional materials for sleeping in lunar gravity.

I tested the model above landing from LLO. The descent stage mass is about 17 tons at touchdown, so the single central SuperDRACO at about 80% thrust hovers nicely, and allows the thrusters to be used to maintain altitude, and adjust laterally to avoid obstacles at the LZ. I reckon the 80% thrust limiter could be preset prior to launch from Earth.

Here is the suggested lunar lander model, including 3 inline Super DRACO engines, Orion pressure vessel with ladder and RTG and additional DRACO thrusters for improved acceleration and redundancy. Ascent vehicle. The Orion pressure vessel upper stage is re-usable and is able to transit from LLO to NRHO using only DRACO thrusters. The upper stage has a wet mass of 4.6 tons (excluding crew and logistics) so could be launched on a Falcon 9 or Vulcan, and transit autonomously to the LOP-G utilising its DRACO thrusters. Since it is re-usable, only one launch is required across the Artemis program. Ascent vehicle launching from the lunar surface after separation from the descent stage. Lander stage 2 is full expendable. Comprises: 4 x drop tanks which are jettisoned after the LOP-G to LLO transit 4 x fuel tanks with lander legs for the descent from LLO to lunar surface 1 x Ascent vehicle tank with 3 x SuperDRACO engines This craft has a wet mass of 31 tons but may be launched (partially fueled) comanifested with the crewed Orion on the SLS, docking directly with the Ascent Vehicle upper stage at the LOP-G Modified Cygnus type refueller able to transit autonomously to the LOP-G, dock and utilise the ESPRIT module to deliver up to 10 tons of payload, including logistics and hypergolic propellant. Two refuelling / reprovisioning missions using a Falcon Heavy LV is required per lunar landing mission.

I would have thought that building a lightweight airlock internal to the Orion made sense, since it is very roomy and likely there will be only 2 crew for lunar landings. I have been thinking that for greatest efficiency, the craft would leave behind the fuel tanks associated with the descent phase on the surface (like Apollo). Unlike Apollo it would jettison the engines and fuel tank prior to reaching LLO, and have one remaining integrated fuel tank for feeding the thrusters with enough fuel to reach NRHO. Interesting. If it is feasible to reduce the mass by removing re-entry components, each kg saved makes a big difference to the size of the completed craft. I am proceeding with an assumed lander mass of 4.0 tons. Good point. However my understanding is the Dragon2 is more massive even than Orion. Not sure what the mass is with all the re-entry components stripped away. It's obvious that the big cost is getting (I calculate) over 26 tons of propellant to the LOP-G per mission. In the absence of ZBO, delivering storable fuels is expensive.

Anything human rated is going to be expensive, obviously. Fixed price is usually the most expensive means of procurement because the risk is entirely borne by the supplier, so there needs to be contingency built into the price. Lockheed Martin designed their 100% re-usable lunar lander with an Orion pressure vessel for a reason - they must be thinking it will be overall commercially competitive compared to a craft with a brand new, purpose-built AV. Consider the issue of testing, Orion with all its features is already nearly fully tested for human rating. How much would it cost to build an alternative, and test it? Using Orion would appear to be a no-brainer from a commercial perspective. But is it too heavy?

I would suggest then 3 x SuperDRACOs inline. The engines will be fired for LLO insertion (x3), then again for descent from LLO to surface. At landing the outer engines are cut, and only the central engine is fired at 20% thrust with DRACO thrusters providing fine adjustment. If the central engine fails or there is a problem with landing, aborting will involve firing the two outer engines to return directly to LLO. If either of the 2 outer engines fail, the central engine is used at full thrust to return to LLO. These engines are ejected during ascent, just prior to reaching LLO so they will quickly degrade in orbit and impact lunar surface. DRACO thrusters engines are used to complete LLO and go to NRHO for rendezvous with the LOP-G. A new SuperDRACO engine set is delivered with each new descent stage, and replacement of any failed DRACO thrusters deployed by Canadarm at the LOP-G. @tater obviously there is a reason the Orion is so expensive - it has a lot of redundant features for extended space flight for a relatively large crew. Anything with a human rating is going to be tested and proved by R&D to the nth degree. So a suitable human rated lander for 2 weeks deployment on the lunar surface, with all the necessary features, is going to be a costly beast regardless of who builds it. Leveraging features already designed and tested for Orion is only going to help the bottom line. Re-usability of the module will also assist. SSTU Labs model of the Orion capsule estimates that a heavy heat shield with ablator = 796 sufficient for re-entry from lunar orbit, has a mass of 2.9 tons. Their model for an Orion orbital craft (no chutes or heat shield) has a dry mass of 3.4 tons.

I think this option would favour the exclusive use of lower cost SuperDRACO engines (expendable) and DRACO RCS thrusters (re-usable on the AV). Perhaps for pressure vessel - a smaller lighter orbital/non-re-entry version of the Orion capsule, otherwise using identical electronics and facilities?

In my simulation I assumed re-usable AV and TV (all the literature points to this as NASA's preferred option) and redocking in LLO with refuelling only at LOP-G using the ESPRIT module to allow multiple lunar landings with only the DV being expendable (remains on the lunar surface ala Apollo). Technically it works, plane changing was not a big issue, although the craft did need a few days in flight to reach LOP-G, (I don’t have access to a super computer to time launches to the second to allow a minimal rendezvous time). Also I have assumed a very small and probably unrealistic lightweight 2-man AV. I think it makes sense to have a re-usable AV that can travel from lunar surface to LOP-G, and an expendable descent vehicle with a drop tank. The problem I am finding is that for a realistic AV mass, the whole craft requires 5 heavy launches (including SLS/Orion) for each lunar landing. I don't think that is going to be commercially viable.

Scott Manley's take on the Artemis moon lander. Even his 3 stage lander is huge. I like the idea that the transit stage is merely a fuel tank that attaches to the top of the ascent vehicle allowing refuelling in LLO before the Ascent stage returns to the LOP-G. Thrusters could be used to de-orbit the third stage for disposal. This is leading me to believe the most efficient design will be a small, lightweight, 2-man ascent stage, utilising 2 x 2 AJ10-190 engines and 16x hypergolic thrusters on each stage.