Jump to content

[New] Space Launch System / Orion Discussion Thread


Recommended Posts

15 minutes ago, tater said:

Um, no.

So she's saying that she thinks that the fact that the majority of launches are commercial is somehow less efficient. She's delusional. Minus commercial launches Artemis reaches the Moon, let's see, multiply by.... add... carry the 2...

Never.

 

I may be team anti-SpaceX but I’m not stupid. Commercial is essential to us going back. NASA is only launching crew. NASA only has one rocket and it’s niche is solely crewed launch capability to lunar orbit. They can’t (ignoring shouldn’t) use SLS for such simple cargo as LOP-G. Even at the peak of SLS proposed production pace- it’d be 2030 or later before we even have the same amount of hardware as we would after 5 years using commercial. Falcon Heavy, Ariane 5 and the Atlas V are all trusted vehicles capable of doing the job cheaper, faster and on time.

Link to comment
Share on other sites

As someone on "team anything but SLS", Orion could be launched on New Glenn and have nearly the same capabilities as an SLS block 1 launch for a fraction of the cost, and use the same architecture that's already in place. The only way SLS is useful if if you cancel block 1 and go straight to 1B or 2, and even that is stretching the word useful because its so prohibitively costly and has such an anemic launch rate. 

Link to comment
Share on other sites

3 minutes ago, ZooNamedGames said:

I may be team anti-SpaceX but I’m not stupid. Commercial is essential to us going back. NASA is only launching crew. NASA only has one rocket and it’s niche is solely crewed launch capability to lunar orbit. They can’t (ignoring shouldn’t) use SLS for such simple cargo as LOP-G. Even at the peak of SLS proposed production pace- it’d be 2030 or later before we even have the same amount of hardware as we would after 5 years using commercial. Falcon Heavy, Ariane 5 and the Atlas V are all trusted vehicles capable of doing the job cheaper, faster and on time.

If there is some congressional move to eliminate the large majority of Artemis launches, then it's dead in the water. They would literally have to fly 3 SLS right after each other (faster than they could possibly stack them in the VAB) to accomplish this, and that's without Gateway, I'm just talking about a lander stack to NRHO, with Orion going last and just hanging out (with some Gateway part already there, launched by a previous SLS---which of course cannot even start happening until Block 1b.

Also, why would you be "team anti-SpaceX"? I'm certainly not "team anti-NASA," after all. I'm against SLS because I think it's not fit for purpose (assuming someone can name me a purpose it was designed for), and at great cost into the bargain. I'm not "team anti-Blue Origin" or team "anti-ULA," either. The more the merrier.

Link to comment
Share on other sites

22 hours ago, tater said:

Um, no.

So she's saying that she thinks that the fact that the majority of launches are commercial is somehow less efficient. She's delusional. Minus commercial launches Artemis reaches the Moon, let's see, multiply by.... add... carry the 2...

Never.

It's a way more complicated issue than you're making it out to be, and I'm quite confident those comments were made in reference to the lander.

If you look behind the scenes, you'll notice that a portion of NASA that was previously on-board with a 3-stage commercially-launched lander design is now pushing for a 2-stage design, with one of the modules launched on cargo SLS.

What's essentially happened is that it's become quite clear that the 3-stage design is too limited to allow use of anything but hypergolics, which basically precludes any future ISRU compatibility, something that quite a few people at NASA think is important. At least one of the bidders seems to think something similar. After all, there would be no need to clarify cargo SLS is on the table for lander bids if someone didn't ask.

Now in a manner not at all dissimilar to what some SLS opponents have done, some people in that camp (such as Cooke) have accused NASA of pursuing the 3-stage design to prop-up commercial launches as industry demand is slumping.

I "bought" this explanation initially, but the guy I talk to at MSFC didn't agree with it. He thinks it's just a realization that came with moving from preliminary studies to actual analysis. In other words, it looked good on paper but now the flaws of that approach are very apparent. He made a pretty strong argument that it wasn't politically-driven in nature, and I found it hard to disagree with him.

Anyway, it's just a complicated issue all around. The HLS lander has long-since outgrown the co-manifested payload capacity of Block 1B, and sizing it down to fit on FH is doable, but maybe not desirable. A separate cargo SLS launch is looking relatively attractive at this point - at least for the descent stage.

Edited by jadebenn
Link to comment
Share on other sites

2 hours ago, jadebenn said:

If you look behind the scenes, you'll notice that a portion of NASA that was previously on-board with a 3-stage commercially-launched lander design is now pushing for a 2-stage design, with one of the modules launched on cargo SLS.

Cargo SLS and a cryo lander would required 2 SLS launches within days of each other. That's not a thing.

2 hours ago, jadebenn said:

Anyway, it's just a complicated issue all around. The HLS lander has long-since outgrown the co-manifested payload capacity of Block 1B, and sizing it down to fit on FH is doable, but maybe not desirable. A separate cargo SLS launch is looking relatively attractive at this point - at least for the descent stage.

How, when a non-hypergolic would necessarily have to fly at virtually the same time as the crew launch.

Link to comment
Share on other sites

 

20 minutes ago, tater said:

Cargo SLS and a cryo lander would required 2 SLS launches within days of each other. That's not a thing.

How, when a non-hypergolic would necessarily have to fly at virtually the same time as the crew launch.

There will be two SLS MLs by the time frame the lander is relevant. SLS has an on-pad time of about a week. The only hiccup is that one of the MLs is designed for Block 1 and the other for Block 1B. Thus:

  • Equip one of the unused VAB high bays for Block 1B
  • Stack a crewed Block 1 SLS on ML-1 and a cargo SLS Block 1B on ML-2
  • Roll the crewed SLS Block 1 out and launch it.
  • Have the crew loiter at the Gateway
  • Roll the cargo SLS Block 1B out and launch it
  • Have it rendezvous with the Gateway

Bam! A feasible two SLS launch architecture!

The only long-term issue would be whether to fly Block 1 indefinitely, or bite the bullet and have a gap of no landings for a little while while ML-1 is upgraded to handle Block 1B.

Edited by jadebenn
Link to comment
Share on other sites

The Apollo TLI stack (CSM/LM) was 45.2 tons.

That's a reasonable minimum for doing lander sorties. The Orion CSM is 26t, and Block 1b can throw maybe 37t to TLI. They might squeeze very slightly more, but nothing like 45.2 tons. SLS cannot do Apollo, even with a much smaller CM.

A reusable lander makes no sense at all, BTW. ISRU on the Moon is not a thing. It might be, I hope it is some day, but not now, and certainly not for the next X human landings. A reusable lander is something like the LockMart design they have been floating for Mars. It's an SLS launch, but it's a LEO SLS launch, as it masses 62 tons (22t dry)---that's around 4600 m/s dv, BTW). Given the dry mass, it can get to the Moon, and will have some 15t of props left for LOI (meaning it uses its own RL-10s to get to the Moon). Now we have an empty lander in lunar orbit that requires 40 tons of propellants (it uses most of the remaining 15 tons of props to do the ~1800-1900m/s LOI burn). How do you propose to refill it so that it can land (needs a full tank to do so)? It's cryo, so we can't refill it over months. SLS can only TLI 37 tons, some of which must be dry mass. So we send a reusable lander, then 2 more SLS to fill it, then a 4th for the crew?

12 minutes ago, jadebenn said:

Bam! A feasible two SLS launch architecture!

Assuming a throw away lander that can manage NRHO to lunar surface with the Ascent stage returning to NRHO, then yes.

Now they just need to actually make EUS, and massively improve their ability to make SLS stuff so that they could launch 2 virtually at once.

 

EDIT: alternately, the LockMart lander goes to Gateway, and the LOI burn is a few hundred m/s, and it needs slightly less refilling, but has to spend that dv to get to LLO anyway (4600 m/s is close for a RT from Gateway to the Surface and back).

Assume it needs even 30t of props. What sends 30t of props to Gateway, quickly? 2 FH launches? Is 1 week apart even possible (what about boiloff?). Also, all future missions need the full 40t.

 

Edited by tater
Link to comment
Share on other sites

I should say a reusable lander makes no sense at all with the SLS architecture.

If it can come back to where the propellant is, or if there is a system capable of cost-effectively bringing propellant to it by the Moon in 1 go, then it is. Ie: if there was some LV system that could get 40t to Gateway, then fly back to do it again, that would totally enable this. Of course such a system might be able to skip Gateway and get to the lunar surface and back as well if it had legs...

Link to comment
Share on other sites

13 minutes ago, tater said:

That's a reasonable minimum for doing lander sorties. The Orion CSM is 26t, and Block 1b can throw maybe 37t to TLI. They might squeeze very slightly more, but nothing like 45.2 tons. SLS cannot do Apollo, even with a much smaller CM.

I was unaware that each Apollo landing was done with two Saturn V launches. :P

Seriously though, I think you've misunderstood what I said. The SLS Block 1B wouldn't co-manifest the lander with Orion. It would carry only the lander. Orion and its crew would come up separately on the SLS Block 1.

Link to comment
Share on other sites

15 minutes ago, jadebenn said:

I was unaware that each Apollo landing was done with two Saturn V launches. :P

Seriously though, I think you've misunderstood what I said. The SLS Block 1B wouldn't co-manifest the lander with Orion. It would carry only the lander. Orion and its crew would come up separately on the SLS Block 1.

I didn't misunderstand, I threw in the Apollo baseline for what a minimal lunar surface sortie would take mass wise. The bare minimum is 45 tons to TLI, regardless of the number of launches (where the TLI is to LLO).

Orion CSM is actually lighter than Apollo CSM, but the capsule itself is much heavier, so it has less propellant. A minimal lander would be the Apollo LM (16.4 tons). That of course requires a lander that only ever operates to and from LLO, however. Since Orion cannot do LLO, the lander then has to go from Gateway to the surface, and the ascent stage comes back to Gateway. This is a substantial mass change. In addition, with 2 launches the lander ALSO has to do the LOI burn, which at least at Gateway is not so bad. The end result is that the lander doesn't need 4400 m/s, it needs maybe 1000 m/s more (a few hundred for LOI at Gateway, and 7-800 m/s to LLO) to get to the surface, and the ascent stage needs an extra 7-800m/s to get back to Gateway (less prop because only the ascent stage). So we need a lander with like 6.2km/s of dv (again, this is slightly confusing because the descent stage needs maybe 3200 (LOI+transfer to LLO), and the ascent stage (smaller) needs maybe 3000 m/s).

Looks like that LockMart lander cannot in fact do a surface sortie from Gateway, actually. It needs a tug to/from LLO, it only has RT props from and to LLO. They'd need to lose about 4-8 tons of dry mass, then it could work (all the aero stuff for Mars could go, except they show it launching without a fairing because it has the aeroshell, minus that it needs a fairing.

 

Edited by tater
Link to comment
Share on other sites

36 minutes ago, tater said:
51 minutes ago, jadebenn said:

The SLS Block 1B wouldn't co-manifest the lander with Orion. It would carry only the lander. Orion and its crew would come up separately on the SLS Block 1.

I didn't misunderstand, I threw in the Apollo baseline for what a minimal lunar surface sortie would take mass wise. The bare minimum is 45 tons to TLI, regardless of the number of launches (where the TLI is to LLO).

Orion CSM is actually lighter than Apollo CSM, but the capsule itself is much heavier, so it has less propellant. A minimal lander would be the Apollo LM (16.4 tons). That of course requires a lander that only ever operates to and from LLO, however. Since Orion cannot do LLO, the lander then has to go from Gateway to the surface, and the ascent stage comes back to Gateway. This is a substantial mass change. In addition, with 2 launches the lander ALSO has to do the LOI burn, which at least at Gateway is not so bad. The end result is that the lander doesn't need 4400 m/s, it needs maybe 1000 m/s more (a few hundred for LOI at Gateway, and 7-800 m/s to LLO) to get to the surface, and the ascent stage needs an extra 7-800m/s to get back to Gateway (less prop because only the ascent stage). So we need a lander with like 6.2km/s of dv (again, this is slightly confusing because the descent stage needs maybe 3200 (LOI+transfer to LLO), and the ascent stage (smaller) needs maybe 3000 m/s).

Hmm.

Let's allow 50% mass growth over the Apollo ascent module, since we obviously wouldn't be satisfied with just replicating Apollo. The ascent vehicle had a wet mass of 4.7 tonnes, of which 2.55 tonnes were props, and had 2.22 km/s of dV. Trying to pull off cryos for the ascent module is just ridiculous, so we'll stick with hypergols. To be generous, we'll boost up to 316 s of isp on the ascent propulsion system, which will get us to 2.42 km/s. Still not enough for the gateway. Let's pile on pure props to get to 3 km/s. That puts us at a wet mass of 8.49 tonnes for the ascent module; we'll round up to 8.6 tonnes to allow for tankage and propulsion system mass growth.

So our cryogenic lander, launched on SLS, needs to deliver 8.6 tonnes from TLI to gateway and then from gateway to the lunar surface. You need 420 m/s from TLI to gateway, 730 m/s from gateway to polar LLO, and 1,870 m/s from LLO to the surface: 3020 m/s. It's going to need margin for correction and boiloff so let's give it 3.1 km/s total to be fair.

Just for a baseline, let's develop our descent module based on the Delta Cryogenic Second Stage formerly used on Delta III, because I suspect it will come out to the right ballpark. Dry mass is 2.5 tonnes; let's grow that to 2.8 tonnes to allow for landing legs and other lander-y stuff. This brings our lunar touchdown mass to 11.4 tonnes, which with a single RL-10 is about one gee. With the amazing 462 s isp of the RL-10, you only need 11.2 tonnes of props to get 3.1 km/s, bringing the total mass SLS must throw to TLI to only 23 tonnes, well within the performance of even SLS Block 1.

So it's doable, but only with cryos.

Link to comment
Share on other sites

8 minutes ago, sevenperforce said:

So it's doable, but only with cryos.

The trouble of course is boiloff, and launch cadence.

What's the minimum time between launches possible for SLS (both technically from a VAB/pad standpoint, and realistically from a production standpoint)?

Does that time frame allow rendezvous at NRHO? Looks like there are a few opportunities each month for TLI to Gateway, so that's at least not too much of an issue (assuming scrubs don't force a wait of a week or more).

Is that architecture cheaper than the alternatives?

Another point: is the very slightly larger lander useful? It seems like any mission that doesn't exceed Apollo surface capabilities is a waste of time. Longest lunar EVA total was Apollo 17, with over 22 hours of surface EVA. All the Apollo evas were jam packed into a short surface stay. I think we'd need more than that, or why bother? (it's not like 2024 is happening, anyway, might as well get it right). Still, there's margin for a bigger lander (most of the "bigger" part is volume, anyway, not mass).

 

Link to comment
Share on other sites

1 hour ago, tater said:

Another point: is the very slightly larger lander useful? It seems like any mission that doesn't exceed Apollo surface capabilities is a waste of time. Longest lunar EVA total was Apollo 17, with over 22 hours of surface EVA. All the Apollo evas were jam packed into a short surface stay. I think we'd need more than that, or why bother? (it's not like 2024 is happening, anyway, might as well get it right). Still, there's margin for a bigger lander (most of the "bigger" part is volume, anyway, not mass).

The HLS (Human Lander System) is baselined with a 7-day surface stay - a little more than twice the length of the longest Apollo stay. For the initial landings, however, the EVA time is supposed to much lower than that full time frame. Because the suits have to be rushed for the first landing, it'll be approximately equal to the Apollo 17 EVA length, despite the longer stay.

Longer EVAs should be possible with better suits - the lander isn't the limiting factor there. This is actually a thing that will be improved if the landing date slips: The lunar suit designs could really use the extra time.

Edited by jadebenn
Link to comment
Share on other sites

1 hour ago, tater said:

What's the minimum time between launches possible for SLS (both technically from a VAB/pad standpoint, and realistically from a production standpoint)?

Production is the bottleneck. The ML would be the bottleneck, if not for the fact that there's going to be two of them now. I'm pretty sure you'd max-out the VAB before you maxed-out pad 39B, though that's highly dependent on how long stacking takes.

You might be able to make pad  39B the bottleneck if you had all 3 of the NASA high bays stacking SLSes on 3 Mobile Launchers, but that's literally peak-Apollo levels of rocket production. The loss of pad 39A to SpaceX hurts redundancy, not launch cadence.

Link to comment
Share on other sites

Still, I don't see a cryo lander as a good idea unless there is already a prop depot (something that makes little sense at the Moon if the props come from Earth, IMHO), or IVF is already flying at the very least. I think it's bad entirely from the logistical standpoint. EoR can give you windows most days. Scrub (a common thing with all LVs)? No worries. NRHO has a period of something like 6.5 days I think. If it takes you a week to get out to the pad, then the next launch is really 13 days from the first launch, not 7 (assuming there's a window every week). There might be some slop there by adjusting the TLI burn, assuming there's margin to do this. Even if the window is a few days, that is setting up timing issues, since each scrub day might have an opportunity the next day using some margin, or the following with more excess props required, etc. This could also possibly impact the LOI burn as well (margin required for this on the lander, though faster transit might come out in the wash vs boiloff).

Still, with 1 flight a year on crew, you could very well end up with Orion stuck at Gateway, and they run out of time for a landing attempt (second SLS waiting to leave). I think I'd prefer the lander be there ahead of time.

Edited by tater
Link to comment
Share on other sites

1 hour ago, tater said:

The trouble of course is boiloff, and launch cadence.

What's the minimum time between launches possible for SLS (both technically from a VAB/pad standpoint, and realistically from a production standpoint)?

I did allow for boiloff.

Launch cadence isn't as big of an issue if you have a little extra propellant margin. You can send Orion to the Gateway and if they need to extend their mission by an extra two weeks because the second SLS slips, nbd.

1 hour ago, tater said:

Another point: is the very slightly larger lander useful?

I would say no.

Though the architecture does allow for the same lander to drop 10 tonnes of downmass on the moon as a precursor. So that's nice.

Link to comment
Share on other sites

Why does the NASA graphic on Artemis-1 have such a bizarre mission length?

26-42 days? DRO is 6-23 days, return transit to Earth (outbound not listed) is listed as 3-11 days.

That implies that getting to DRO takes 17 days, min? (min DRO+min transit back to Earth = 6+3)

Seems like the min mission must be closer to12-13 days, not 26.

Forgot image:

Artemis1_mission-map_2019.jpg

Link to comment
Share on other sites

1 minute ago, tater said:

That implies that getting to DRO takes 17 days, min? (min DRO+min transit back to Earth = 6+3)

Point 12 on the graphic states that Orion remains in DRO for 6-23 days.

IIRC, transit to NRHO takes 7 days, and transit to LLO takes 3.

Link to comment
Share on other sites

52 minutes ago, jadebenn said:

Point 12 on the graphic states that Orion remains in DRO for 6-23 days.

IIRC, transit to NRHO takes 7 days, and transit to LLO takes 3.

The chart is Artemis-1, there is no LLO, it's not NRHO, it's DRO.

So minimum DRO is 6 days. Minimum return on that graphic says 3 days. That's 9 days. The bottom says the minimum duration of the total mission is 26 days. That means that transit to DRO must take 15 days according to the NASA graphic.

(I'm saying their graphic is clearly wrong)

Link to comment
Share on other sites

This thread is quite old. Please consider starting a new thread rather than reviving this one.

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...