totm dec 2023 Artemis Discussion Thread

[jinnantonix]

10 hours ago, sevenperforce said:

It would be far easier, I think, to replace drop tanks manually using a Canadarm than to master multi-tonne hypergolic propellant transfer. More mass-efficient, too.

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. 

[tater]

Blue, LockMart, and Grumman working together:

Quote

Today, Blue Origin is proud to announce a national team to offer a Human Landing System for NASA’s Artemis program to return Americans to the lunar surface by 2024.
 
Blue Origin has signed teaming agreements with Lockheed Martin, Northrop Grumman and Draper. These partners have decades of experience supporting NASA with human space flight systems, launch vehicles, orbital logistics, deep-space missions, interplanetary navigation and planetary landings.
 
Our combined experience is uniquely positioned to meet NASA’s needs for the Artemis program. Each partner will bring their industry leading solutions to the following roles:

• Blue Origin, as prime contractor, leads program management, systems engineering, safety and mission assurance, and mission engineering while providing the Descent Element that is based on the multi-year development of the Blue Moon lunar lander and its BE-7 engine.
  
• Lockheed Martin develops the reusable Ascent Element vehicle and leads crewed flight operations and training.
  
• Northrop Grumman provides the Transfer Element vehicle that brings the landing system down towards the Moon.
  
• Draper leads descent guidance and provides flight avionics. 

“National challenges call for a national response. We are humbled and inspired to lead this deeply committed team that will land NASA astronauts on the Moon,” said Bob Smith, CEO, Blue Origin. “Combining our partners’ heritage with our advance work on the Blue Moon lunar lander and its BE-7 engine, our team is looking forward to working with NASA in support of the Artemis program.” 
 
“Lockheed Martin has been honored to help NASA explore space for more than 50 years, providing deep space robotic missions, planetary landers, space shuttle heritage and the Orion exploration spacecraft,” said Rick Ambrose, executive vice president, Lockheed Martin Space. “We value Blue Origin’s thoughtful approach to developing human-rated flight systems, and are thrilled to be part of a national team with this mix of innovation and experience. We look forward to safely and sustainably returning our nation to the surface of the Moon by 2024.”
 
“Northrop Grumman’s commitment to put Americans back on the moon dates back over 50 years ago with the delivery of the first lunar lander for the historic Apollo Program,” said Blake Larson, corporate vice president and president of Innovation Systems, Northrop Grumman. “Along with our ongoing work on the Space Launch System boosters, astronaut escape system, and the Gateway habitat, we are proud to be a part of the Blue Origin national team to support NASA’s Artemis program and the ambitious goal to return to the moon by 2024.”
 
“When the nation needs precision guidance, it calls on Draper,” said Kaigham J. Gabriel, President and CEO, Draper. “We guided Apollo to the moon and back nearly 50 years ago. We’re ready to do it again with the Blue Origin team for Artemis.” 
 
It’s time to go back to the Moon, this time to stay.
 
-Gradatim Ferociter

 

[tater]

20 hours ago, tater said:

Interestingly, this LockMart mockup can't be based on Orion at all (looks like they used Altair mockup parts).

 

 

19 hours ago, sevenperforce said:

I wanna see more about that first one. Are those radiators on the front?

Looks like those 2 might stack...

I post that, then finally see this tweet:

 

"Leverages" so it's not Orion at all.

[sevenperforce]

12 hours ago, jinnantonix said:

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. 

Well, they don't necessarily need to be stacked by inline docking; they can also be stacked by tangential/perpendicular couplings, if the couplings allow for high-volume flow and structural linkage.

My thought is to use EOR; launch the lander/ascender on one Falcon Heavy, then launch the expendable tanks on another, couple the two, and use the second FHUS for the TLI. Then the lander/ascender serves as the transit vehicle.

21 minutes ago, tater said:

I post that, then finally see this tweet:

 

"Leverages" so it's not Orion at all.

Is there an engine under there?

If it is supposed to be reusable then presumably they are planning for propellant transfer through the forward docking port.

What's the bit with the golden tanks? Is that supposed to be a transfer vehicle? It wouldn't need landing legs.

[tater]

34 minutes ago, sevenperforce said:

Well, they don't necessarily need to be stacked by inline docking; they can also be stacked by tangential/perpendicular couplings, if the couplings allow for high-volume flow and structural linkage.

My thought is to use EOR; launch the lander/ascender on one Falcon Heavy, then launch the expendable tanks on another, couple the two, and use the second FHUS for the TLI. Then the lander/ascender serves as the transit vehicle.

Is there an engine under there?

If it is supposed to be reusable then presumably they are planning for propellant transfer through the forward docking port.

What's the bit with the golden tanks? Is that supposed to be a transfer vehicle? It wouldn't need landing legs.

The golden tank one is a CLPS lander, not crew. The 2 that stack are the LM crew vehicle, and a Blue Moon lander. The BO lander is not the right one, however, Bezos said when they first announced that that the larger payload version was taller (6t vs 3.6t to the surface)

[tater]

Quote

The three-element lander’s descent stage will be powered by Blue Origin’s throttleable BE-7 engine, which burns super-cold liquid hydrogen and liquid oxygen propellants. The Northrop Grumman-made transfer vehicle will also use the BE-7 engine, Bezos said.

From https://spaceflightnow.com/2019/10/22/bezos-says-space-industry-stalwarts-will-help-blue-origin-build-moon-lander/

Assumed the NG contribution was a version of Cygnus. Apparently not.

[sevenperforce]

4 minutes ago, tater said:

Quote

The three-element lander’s descent stage will be powered by Blue Origin’s throttleable BE-7 engine, which burns super-cold liquid hydrogen and liquid oxygen propellants. The Northrop Grumman-made transfer vehicle will also use the BE-7 engine, Bezos said.

From https://spaceflightnow.com/2019/10/22/bezos-says-space-industry-stalwarts-will-help-blue-origin-build-moon-lander/

Assumed the NG contribution was a version of Cygnus. Apparently not.

So, Altair, but with a smaller ascent module and the BE-7 in place of the RL-10.

[jadebenn]

6 minutes ago, tater said:

From https://spaceflightnow.com/2019/10/22/bezos-says-space-industry-stalwarts-will-help-blue-origin-build-moon-lander/

Assumed the NG contribution was a version of Cygnus. Apparently not.

A hydrolox transfer stage? That's a bold move.

[tater]

Note that this puts a lie to any claim that the transfer stage bears any resemblance to Cygnus in a technical way. Totally new vehicle. Cryos, too, which is... bizarre. You'd think that scheduling would make storables what they would want.

[tater]

Just now, sevenperforce said:

So, Altair, but with a smaller ascent module and the BE-7 in place of the RL-10.

Yeah, and a distributed launch scheduling nightmare.

Just now, jadebenn said:

A hydrolox transfer stage? That's a bold move.

Kinda kooky. On the one side they need the 7-800 m/s dv (pushing the entire pander stack!), so high I_sp helps, but the scheduling... seems very, very tight. The benefit of Gateway in this architecture is the ability to stage stuff over time. This basically requires sending everything one after another.

Looks like they have some margin.

[sevenperforce]

1 minute ago, tater said:

Note that this puts a lie to any claim that the transfer stage bears any resemblance to Cygnus in a technical way. Totally new vehicle. Cryos, too, which is... bizarre. You'd think that scheduling would make storables what they would want.

3 minutes ago, sevenperforce said:

So, Altair, but with a smaller ascent module and the BE-7 in place of the RL-10.

...and a distributed launch scheduling nightmare.

The New Glenn user's guide mentions no RCS on the booster but mentions four triaxial RCS thrusters on the upper stage for settling. Some triaxial thrusters are visible here, though this may be artistic license. Pressurization of both stages is confirmed to be autogenous. In the Blue Moon reveal video, we see four triaxial thrusters on the top of the lander and four quintaxial thrusters on the bottom. Bezos discussed that they will use hydrogen boil-off to chill the LOX tanks and then pump the warmed GH₂ into accumulators, along with boiled GOX that goes into its own accumulators. The GH₂+GOX will be used to operate fuel cells, as in the ACES design. 

However, I see no other tanks on the vehicle than the accumulators and the main tanks. If I had to make a wild guess, I would say that the 32 thrusters on Blue Moon are pressure-fed from the accumulators with spark ignition. Alternately, they could be cold-gas thrusters pressure-fed solely from the GH2 accumulators; this avoids the need for ignition altogether. These thrusters can be used for mid-course correction, reducing the impact of boil-off considerably.

[tater]

Yeah, boiloff mitigation buys them... a couple months? That certainly helps. Dunno what the LM stage or the Grumman stage will be able to manage, though.

Send hypergolic Ascent stage ahead, then Blue Descent stage, then transfer stage and then crew?

[sevenperforce]

7 minutes ago, tater said:

Yeah, boiloff mitigation buys them... a couple months? That certainly helps. Dunno what the LM stage or the Grumman stage will be able to manage, though.

Send hypergolic Ascent stage ahead, then Blue Descent stage, then transfer stage and then crew?

Survival on the lunar surface is supposed to run through the lunar night...seemingly multiple cycles, so I expect boil off is low enough for at least a few months, yeah.

The ascent stage is supposed to be reusable. I would think they send the descent stage first, then the crew, then the transfer stage carrying the propellant to refuel the ascent stage. Ordering of the last two is optional.

[jinnantonix]

10 hours ago, sevenperforce said:

Well, they don't necessarily need to be stacked by inline docking; they can also be stacked by tangential/perpendicular couplings, if the couplings allow for high-volume flow and structural linkage.

My thought is to use EOR; launch the lander/ascender on one Falcon Heavy, then launch the expendable tanks on another, couple the two, and use the second FHUS for the TLI. Then the lander/ascender serves as the transit vehicle.

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...

 

 

 

Edited October 23, 2019 by jinnantonix

[tater]

42 minutes ago, jinnantonix said:

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.

Yeah, because autonomous docking and assembly around the Moon is easier and less risky than LEO (this isn't  a poke at you, every time EoR comes up WRT the Moon and Artemis in here rendezvous and docking is somehow hard, but around the Moon it's not. For reasons.)

[jinnantonix]

8 minutes ago, tater said:

Yeah, because autonomous docking and assembly around the Moon is easier and less risky than LEO (this isn't  a poke at you, every time EoR comes up WRT the Moon and Artemis in here rendezvous and docking is somehow hard, but around the Moon it's not. For reasons.)

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.   

Edited October 23, 2019 by jinnantonix

[kerbiloid]

Probably once they had gotten normal comm&comp tech onboard, the low-speed lunar dockings are more comfy, homish, Kerbal.

[sevenperforce]

11 hours ago, tater said:

12 hours ago, jinnantonix said:

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.

Yeah, because autonomous docking and assembly around the Moon is easier and less risky than LEO (this isn't  a poke at you, every time EoR comes up WRT the Moon and Artemis in here rendezvous and docking is somehow hard, but around the Moon it's not. For reasons.)

Right. Plus, Earth orbit assembly allows a single TLI burn, a single lunar powered flyby, and a single LOP-G rendezvous. So it's more mass-efficient by definition, because you have less dry mass going to LOP-G.

If you build the tanks larger, then that's more dry mass wasted at LOP-G, and conceivably more dry mass being hauled down to LLO and even further.

 

[tater]

So the Stretched Blue Moon stage gets 6.5t cargo to the surface. That means the LockMart Ascent stage has 6500 kg (wet) to get crew presumably back to Gateway. It has some crew, and presumably collects rocks, etc, so it needs to have a dry mass under 2.5t by some amount to have the dv to make it back to Gateway.

I'd assume they use the same OMS engines as Orion, or some other AJ-10 variant (so 319s I_sp) because it's survival critical that it works (such a choice gives it just shy of 3000m/s with a 2.5t dry mass).

[sevenperforce]

24 minutes ago, tater said:

So the Stretched Blue Moon stage gets 6.5t cargo to the surface. That means the LockMart Ascent stage has 6500 kg (wet) to get crew presumably back to Gateway. It has some crew, and presumably collects rocks, etc, so it needs to have a dry mass under 2.5t by some amount to have the dv to make it back to Gateway.

I'd assume they use the same OMS engines as Orion, or some other AJ-10 variant (so 319s I_sp) because it's survival critical that it works (such a choice gives it just shy of 3000m/s with a 2.5t dry mass).

Any indication on how the LockMart Ascent stage is supposed to be reused? Are they going to refuel with prop transfer at LOP-G?

If they went with a pump-fed engine they could save enough in tankage dry mass to afford two engines, which gives them engine-out capability.

[StrandedonEarth]

2 hours ago, sevenperforce said:

If they went with a pump-fed engine they could save enough in tankage dry mass to afford two engines, which gives them engine-out capability.

...until you discover a flaw common to both engines, while on the lunar surface. 
Lunar ascent engines are dead simple (open/close valves) because they absolutely have to work. Simplicity beats out complex redundancy. 
 

I want to think they can just use SS to bring the Lockmart AV back to LOP-G...

[sevenperforce]

Upon review of the drop tank architecture...if we are doing hypergolics, there is no need for multiple engines. One will do. A downthrottled vacuum-expanded Superdraco can get no lower than 12 tonnes lunar thrust, so it is just too thrusty. A deep-throttling AJ-10 or comparable engine will need to be used instead. 

@tater gives the BlueMoon+LockMart ascent vehicle a dry mass of 2.5 tonnes, but I'll be a touch more generous and say 2.8 tonnes (assuming 319 s Isp, 2.6 km/s from lunar surface to LOP-G, 6.5 tonnes on the surface). Those 3.7 tonnes of props will require a tankage dry mass of 630 kg and of course 100 kg of AJ-10 engine, leaving the crew vehicle plus control thrusters at a mass of about 2,070 kg.

So if that's our goal, let's see what the reusable-crew-taxi-with-drop-tanks approach will get us. Let's say it has Draco thrusters at 300 s Isp and performs the last 200 m/s of LLO circularization after the lander/ascent module ("LAM") is jettisoned. It needs a dV of 930 m/s to circularize and return to LOP-G. It needs 822.3 kg of props and with 139.7 kg of tankage, so our drop tank will mass 962 kg and our "crew taxi" will mass 3,032 kg at LAM separation.

Let's throw on 100 kg for the AJ-10 at 319 s. If we bolt four of those same expendable tanks around the engine on the lander/ascender, we end up with 1.992 km/s on the vehicle, which gets you into LLO easily. Since you only need 1.67 km/s (since the crew taxi does the circularization), you only need 2,606 kg of props for ascent, leaving you with 683 kg of props for final approach and landing.

Of course, on the surface, you're going to need to support the landed mass of 6,297 kg. Let's add the 9.4% structural fraction for landing legs, ladder, and associated compressive structure that will be jettisoned at takeoff (landing mass is 6,889 kg, which can be hovered if you downthrottle to 11.1 kN, or about 25% of max thrust on an AJ-10). That additional 592 kg gives us a lander/ascender dry mass (including the four bolted tanks) of 1,251 kg and means our 683 kg of propellants allow us to handle the last 296 m/s of descent and landing. Accordingly, our transfer vehicle would need to provide 2,304 m/s from LOP-G to the lunar surface.

If we use the lander/ascender's AJ-10 to accomplish that with drop tanks, we will need larger drop tanks with a total of 10.13 tonnes of propellant and 1.72 tonnes of tankage. Remember, however, that the crew taxi is reused every flight, so that's 2,070 kg you don't have to throw to TLI or brake into TLI. With this caveat, the total delivery to LOP-G for each completed sortie becomes 17.35 tonnes. Rendezvous of THAT to LOP-G from TLI requires another 430 m/s, which is 2,624 kg of propellant and 446 kg of drop tankage. Total mass sent to TLI: 20.42 tonnes.

You can easily put 20.42 tonnes into LEO with a triple-core-recovery Falcon Heavy and then send up an expendable Falcon Heavy with a naked upper stage and a docking ring to throw that into TLI.

Edited October 23, 2019 by sevenperforce

[sevenperforce]

I did leave a little bit of optimization on the table with this analysis, based on drop tank size. The size of the drop tank on the crew taxi is constrained -- you don't want to give it much more dV responsibility or you end up with a potential thrust shortfall -- but making the "built-in" tankage on the LAM exactly four times more was arbitrary. I could have made them bigger, which means they take over earlier in the descent, or smaller, which means they would do less of the descent and essentially take over just before landing. Probably best to make them as small as possible, but getting rid of the dry mass of the transfer tanks early is important too.

If the ~20-tonne stack is launched monolithically into LEO, all the drop tank couplings can be performed on the ground, which is obviously preferred. It is hard enough to design drop tanks without having to worry about attaching them on orbit. The drop tank on the crew taxi would of course need to be attached at LOP-G, but since it is not removed until the return, it isn't a "drop" tank in the same way. The tanks would have valves to determine drain priority, which is also straightforward enough. The iterated-drop-tank design has fairly good abort characteristics; the crew taxi can separate and return to LOP-G if there is a problem up through LLO, and can correct a serious thrust/fuel anomaly on ascent by completing part of the ascent on thrusters alone (though it would then need a rescue mission).

The LAM+taxi architecture would benefit from using RD-4 thrusters, which boast higher specific impulse and higher thrust than the Dracos. The extra 4.5% in Isp for the taxi element reduces mass by a few percent all the way down the line. It could also be used in conjunction with a cryogenic transfer stage. If the LAM alone was launched onto TLI, it would need only a small drop tank to brake itself into rendezvous with LOP-G -- almost exactly the size of the one on the crew taxi -- and total mass to TLI would be just 6,473 kg!

Towing that (minus rendezvous drop tank, plus the crew taxi) from LOP-G to within 300 m/s of the lunar surface is still 2,304 m/s, but with cryogens it gets more interesting. Using the RL-10, for example, you only need about 5.5 tonnes of hydrolox in a balloon tank. Of course, that transfer stage needs to get itself to LOP-G, which means it needs RCS thrusters and another 430 m/s of dV, but you only have to throw about 7-8 tonnes to TLI.

[sevenperforce]

On a final note -- I have not yet done the math, but I think it is very close whether an expendable Falcon Heavy could reach LOP-G with the FHUS still attached to the LAM and still have enough kerolox reserves to act as the crasher stage from LOP-G through LLO to the lunar surface. An expendable Falcon Heavy with crossfeed could probably pull it off.

[jadebenn]

This is relevant to the Artemis thread as well; Boeing's lander bid will be SLS-launched:

I don't want to say I called it... but I totally called it. 

Edited October 24, 2019 by jadebenn