totm dec 2023 Artemis Discussion Thread

[Ultimate Steve]

47 minutes ago, jinnantonix said:

I thought Northrop Grumman was a shoe-in with a modified Cygnus XL, but well done SpaceX.

There are two different providers that will be awarded contracts, I think, so they could still win the second slot.

[jadebenn]

6 minutes ago, Ultimate Steve said:

There are two different providers that will be awarded contracts, I think, so they could still win the second slot.

Indeed, and I very much expect they will.

3 hours ago, Nightside said:

I'm sure the dragon will need a few tweaks to get it to the moon and back, but probably not much.

That looks like a heck of a lot more than "a few tweaks."

[tater]

How would they launch Cygnus to TLI? Antares basically gets it to LEO with some decent margin, but nothing like enough dv for TLI. F9 could do it, actually.

[Ultimate Steve]

1 minute ago, tater said:

How would they launch Cygnus to TLI? Antares basically gets it to LEO with some decent margin, but nothing like enough dv for TLI. F9 could do it, actually.

By the time 2024 rolls around there will be many vehicles to choose from. NGIS should have OmegA by then, and if OmegA doesn't pan out, Vulcan will almost surely be ready. As much cost advantage as SpaceX has, it would be unwise to rely on the Falcon family for all of these cargo launches, although the Falcon family is certainly up to the task.

[tater]

46 minutes ago, Ultimate Steve said:

By the time 2024 rolls around there will be many vehicles to choose from. NGIS should have OmegA by then, and if OmegA doesn't pan out, Vulcan will almost surely be ready. As much cost advantage as SpaceX has, it would be unwise to rely on the Falcon family for all of these cargo launches, although the Falcon family is certainly up to the task.

I totally spaced Omega. Yeah, that works.

 

[jadebenn]

Well, it doesn't look like we're getting Lunar Cygnus after all.

Spaceflight Now's article has some more deets on the contract award, and it looks like SpaceX is slated to be the only provider.

Quote

Mark Wiese, deep space logistics manager at NASA’s Kennedy Space Center in Florida, said the agency considered selecting more than one cargo transportation provider for the Gateway, but eventually settled on picking a single contractor. NASA could open up the Gateway Logistics Services contract to more companies in the future, but there is no specific timetable to do so, he said.

 

[sh1pman]

 

[Nightside]

14 hours ago, jinnantonix said:

I thought Northrop Grumman was a shoe-in with a modified Cygnus XL, but well done SpaceX.

Maybe they couldn’t stomach flying on another rocket if omega doesn’t get off the ground soon. Haven’t heard much about that project lately.

[Nightside]

13 hours ago, jadebenn said:

That looks like a heck of a lot more than "a few tweaks."

I didn’t realize that was a definitive model.

It’s a new form factor for SpaceX but it looks much like every other CTS supply ship. Aside from some increases to fuel cap, And tougher electronics, it’s is a much simpler craft than Dragon 1/2.

[tater]

5 hours ago, sh1pman said:

 

I still think it's pointless.

[Ultimate Steve]

3 hours ago, tater said:

I still think it's pointless.

My personal opinion is that the idea of a lunar station itself is far from pointless, but Gateway's location is kinda pointless, mostly where it is because Orion never got a better service module post constellation. The orbit does offer some advantages above frozen polar llo, like constant sunlight and comms, but not really worth the delta v hit for the Landers imo if we are considering this from strictly an engineering standpoint.

However, the idea of a lunar space station, no matter what orbit, has major benefits in areas outside of engineering. Once gateway or another station is up, canceling Artemis is less politically feasible, as we have permanent expensive infrastructure in place, and if current plans progress, international partners will also play roles in it's construction, adding more support and momentum to manned lunar operations. This should help Artemis be more than just flags and footprints. If an extra few hundred m/s to a detour orbit and disproportionately large landers is what it takes to make this more than just a few missions then a cancellation, then so be it in my opinion.

[magnemoe]

4 hours ago, tater said:

I still think it's pointless.

It makes sense if you do lots of moon landing or set up an large base. In an Starship time it might be, starship can be landed on moon but it require lots of refuelings. Having an reusable lander will require much less fuel even if SSTO. 

[RCgothic]

2 hours ago, Ultimate Steve said:

My personal opinion is that the idea of a lunar station itself is far from pointless, but Gateway's location is kinda pointless, mostly where it is because Orion never got a better service module post constellation. 

SLS can't boost Orion plus a better service module.

[RealKerbal3x]

39 minutes ago, RCgothic said:

SLS can't boost Orion plus a better service module.

And this is what happens when you design a rocket and then work out what you want it to do.

Edited March 28, 2020 by RealKerbal3x

[V_Bomb2001]

8 hours ago, Nightside said:

Maybe they couldn’t stomach flying on another rocket if omega doesn’t get off the ground soon. Haven’t heard much about that project lately.

OmegA has been progressing well recently:

Spoiler

https://spacenews.com/northrop-grumman-completes-static-fire-test-of-omega-rockets-second-stage/

Also, has everybody just forgotten that Gateway itself is basically just a heavily modified Cygnus?

[tater]

1 hour ago, V_Bomb2001 said:

Also, has everybody just forgotten that Gateway itself is basically just a heavily modified Cygnus?

Yeah, the base module stuck to the PPE is just a Cygnus variant, right?

[Barzon]

I've heard rumours of rumours that due to Gateway being pushed off the critical path for 2024, NASA might launch an integrated PPE+HALO, so the Cygnus SM might be removed for the actual HALO module.

[tater]

7 minutes ago, Barzon said:

I've heard rumours of rumours that due to Gateway being pushed off the critical path for 2024, NASA might launch an integrated PPE+HALO, so the Cygnus SM might be removed for the actual HALO module.

While I've never been a fan of Gateway for doing anything interesting, it's popular with international partners I guess, so it has a purpose in that regard. Assuming they can actually contribute anything useful.

[jinnantonix]

54 minutes ago, Barzon said:

I've heard rumours of rumours that due to Gateway being pushed off the critical path for 2024, NASA might launch an integrated PPE+HALO, so the Cygnus SM might be removed for the actual HALO module.

Not sure about the SM being "removed".  Rather I would think modified to provide more dV for NRHO injection of the PPE+HALO.  The current SM has limited thrust, as it only provides for LEO orbital manoeuvres.  Would upgrade of the SM be appropriate, or development of a purpose built booster for NRHO injection?

[jadebenn]

The PPE could almost certainly handle moving HALO to TLI, assuming there's no issues with the really long burns required.

[jinnantonix]

7 hours ago, jadebenn said:

The PPE could almost certainly handle moving HALO to TLI, assuming there's no issues with the really long burns required.

Using ion engines to launch a craft from LEO to TLI is a bridge too far, the final stage of the LV would be preferred, or the upper stage of another LV,  separately launched and docked in LEO. 

I also doubt the PPE ion engines would be used to inject into NRHO, a hypergolic fueled booster would be better suited.  The same booster could be used for NRHO injection of each of the Gateway components.  My money is on a modified Cygnus or SpaceX Dragon SM.

[sevenperforce]

13 hours ago, jinnantonix said:

21 hours ago, jadebenn said:

The PPE could almost certainly handle moving HALO to TLI, assuming there's no issues with the really long burns required.

Using ion engines to launch a craft from LEO to TLI is a bridge too far, the final stage of the LV would be preferred, or the upper stage of another LV,  separately launched and docked in LEO. 

I discussed this once with @tater before in the context of delivering landing modules. The time for the PPE to spiral out from LEO to the moon using ions while carrying substantial mass is something on the order of a year of continuous burn time.

Assumptions:

• 7 km/s from LEO to EML-1 using low-thrust spirals
• PPE propulsion: 4x AEPS Hall thrusters at 14 kW consumption, 2600 s isp, 600 mN each
• Propellant: 5000 kg xenon
• System dry mass (estimate): 3 tonnes
• HALO mass: 3.4 tonnes

Maths:

• Total solar-electric dV: 14,710 m/s (good so far)
• Propellant consumption at max thrust: 94.13 mg/s
• Propellant usage to reach 7 km/s: 2.738 tonnes
• Burn time: 2.71e7 sec or 336.66 days

Not undoable -- Hall effect thrusters have built up 8000-hour burn times in testing -- but challenging. For larger modules it is prohibitive. A notional 30-tonne multistage Artemis crew lander would require 10.4 tonnes of xenon and would take 42 months of continuous thrust, or around 3.5 years.

[tater]

What about throwing it to GTO, then letting the PPE move it from there?

(phasing and rendezvous clearly becomes non-trivial to do distributed launch to a highly elliptical orbit)

[sevenperforce]

3 hours ago, tater said:

What about throwing it to GTO, then letting the PPE move it from there?

You need 1.8-2.1 km/s to circularize from GTO to GEO and then you need 1.4-1.8 km/s to spiral from GEO to EML-1. Lots of essentially zero-energy transfers from EML-1 to EML-2 and NRHO. So around 3.55 km/s. Six months of burn time for the HALO (plus time for the transfer to NRHO), 20 months (and 5 tonnes xenon) for a 30-tonne landing module.

 

[tater]

https://www.docdroid.net/EvbakaZ/glssssredacted-version-pdf

Evaluation of the Gateway supply bids.

Quote

For the remaining three offerors, SpaceX had the lowest overall total evaluated price. SNC had the next lowest price, which was significantly higher than SpaceX’s price. NGIS had the third highest price, which was significantly higher than SNC’s price. The SEB also determined the three offerors’ evaluated prices were reasonable and balanced.

Note that in the above Boeing had already been eliminated because of other problems with the bid, but Boeing's cost was substantially higher than NGIS (unsurprisingly).