[New] Space Launch System / Orion Discussion Thread

[tater]

8 minutes ago, YNM said:

Apparently 40 tonnes of cargo to TLI, vs 26 tonnes for Block 1.

Yes, 26t is Orion.

So it buys 14t of comanifested cargo. That's not really a "capability," though. What mission objective is accomplished with this additional mass? Can it then send crew to the lunar surface in 1 launch? Nope. Can it get to LLO? Yeah, the 14t could be a LOI stage. Now we'd have Orion in LLO... for reasons.

9 minutes ago, sevenperforce said:

I could do the math on what that would look like if I wanted to......

What was FH TLI throw? 23t?

Call it 14t just to be safe.

Is the additional cost of EUS greater than FH? If so, it's a total waste of time since the cargo it flies could be sent as... cargo at lower cost.

If FH can instead send more cargo mass, then  EUS looks even worse.

 

[RCgothic]

The standard comeback is that Orion can brake 14t of cargo into NRHO and dock it, so more of that 14t can be payload can be cargo than an equivalent un-comanifested 14t payload.

But as FH can throw much more than 14t to TLI and therefore systems to brake and dock, that's a bit irrelevant

[StrandedonEarth]

17 minutes ago, tater said:

So it buys 14t of comanifested cargo.

Use the  extra 14t to build a proper service module, with oodles of propellant and consumables, which could be transferred to wherever it's needed.

Of course, creating such a beast would take even more money.

[tater]

A better SM would improve Orion, but it's then a huge, expensive LV to get a single capsule to LLO.

15 minutes ago, RCgothic said:

The standard comeback is that Orion can brake 14t of cargo into NRHO and dock it, so more of that 14t can be payload can be cargo than an equivalent un-comanifested 14t payload.

But as FH can throw much more than 14t to TLI and therefore systems to brake and dock, that's a bit irrelevant

Yeah, that's a legit claim, but if FH can send 14t plus a little stage with RCS, etc, then it can bring it to Gateway as well. As uncrewed cargo, there is zero requirement for a fast transit (unless it's cryos).

[YNM]

45 minutes ago, tater said:

So it buys 14t of comanifested cargo.

Most likely not going to be used as comanifest, but rather for dedicated 40 t cargo.

EUS is supposed to be the whole of the first SLS w/o upgraded SRBs (that'd be Block 2) - the ICPS being used merely because EUS isn't available.

However, given that the Mobile Launcher that the Block 1B will go on is apparently only going to be finished in 2023... so idk, just like, suit yourself, whatever that can throw 40 t of cargo to TLI, or just don't make 40 t whole cargo to TLI.

Edited January 29, 2021 by YNM

[tater]

59 minutes ago, YNM said:

Most likely not going to be used as comanifest, but rather for dedicated 40 t cargo.

What 40t cargo do they have, and where is it going?

I wasn't aware of any missions even penciled in for anything other than Artemis.

An HLS system as a cargo makes little sense, as that would involve cryos, and they'd need to launch Orion very rapidly afterwards.

59 minutes ago, YNM said:

EUS is supposed to be the whole of the first SLS w/o upgraded SRBs (that'd be Block 2) - the ICPS being used merely because EUS isn't available.

? I wasn't aware Block 2 was even on the table as a thing any time in the next several years.

 

59 minutes ago, YNM said:

However, given that the Mobile Launcher that the Block 1B will go on is apparently only going to be finished in 2023... so idk, just like, suit yourself, whatever that can throw 40 t of cargo to TLI, or just don't make 40 t whole cargo to TLI.

B1b, yes, that;s the use, which is all Artemis (hence Orion) as far as the eye can see. There are zero payloads that exist except Orion.

[sevenperforce]

Just now, tater said:

Yes, 26t is Orion.

So it buys 14t of comanifested cargo. That's not really a "capability," though. What mission objective is accomplished with this additional mass? Can it then send crew to the lunar surface in 1 launch? Nope. Can it get to LLO? Yeah, the 14t could be a LOI stage. Now we'd have Orion in LLO... for reasons.

What was FH TLI throw? 23t?

Call it 14t just to be safe.

Is the additional cost of EUS greater than FH? If so, it's a total waste of time since the cargo it flies could be sent as... cargo at lower cost.

If FH can instead send more cargo mass, then  EUS looks even worse.

Yep.

Let's do the gorram math then. SLS Block 1 with ICPS can send 27 tonnes to TLI. Orion is 26.52 tonnes at TLI injection so that's the limit of ICPS.

Let's say FH can throw 23 tonnes to TLI, which is probably conservative. 

It costs 730 m/s of dV to get to low lunar orbit and 430 m/s of dV to get to NRHO. With 23 tonnes of injection mass and a 300 s hypergolic insertion stage, it takes 5.1 tonnes of propellant to reach LLO and 3.1 tonnes of propellant to reach NRHO. Borrowing mass fractions from the Delta-K (950 kg empty & 6004 kg props =  15.8% stage mass to prop mass), that means a stage mass of approximately 490 kg for the NRHO insertion stage and 806 kg for the LLO insertion stage. These numbers are conservative because you don't need NEARLY this much thrust for cislunar burns, so your engine mass is going to be lower (300 s is the specific impulse of small pressure-fed Draco thrusters so this is also conservative). So FH can send at least 17.1 tonnes to LLO and at least 19.4 tonnes to NRHO. This is dramatically more than can be co-manifested with EUS and Orion **plus** it arrives at the destination without borrowing any dV from Orion.

 

But wait, there's more!

What if EUS was used in an Earth Orbit Rendezvous architecture?

Orion's service module carries 8.6 tonnes of propellant. Assuming it goes to NRHO, it needs to return itself to Earth entry interface, which costs 410 m/s of dV. Orion's dry mass is (26.52 - 8.6) 17.92 tonnes, so getting back to an Earth entry from NRO is going to cost it 2.54 tonnes of propellant at 316 seconds of specific impulse. Getting from TLI to NRHO costs 430 m/s which is a propellant fraction of 13%. This means the most Orion could actually deliver to NRHO while still retaining enough propellant for return (with NO margin) would be 20.1 tonnes. That's a whole half-tonne more than if you just sent your cargo direct to TLI on FH with an insertion stage!

But hold on. TLI costs 3.2 km/s. The ICPS will have a dry mass of 3.49 tonnes, of which the engine is 301 kg. If the ICPS tankage is 3.189 tonnes to  27.22 tonnes of propellant (11.72% of prop), then the EUS's 129 tonnes of prop mass should correspond to roughly 15.12 tonnes of tankage plus 230 kg*4 = 920 kg of engines for a dry mass of 16.04 tonnes. If EUS can send 40 tonnes to TLI at 460.1 s, then its m₁ would be 40 + 16.04 tonnes which gives an m₀ of 113.95 tonnes in LEO or 57.91 tonnes of propellant in LEO. Tracing the calculations backwards, we know that the staging mass of EUS + 40-tonnes-payload = 185.04 tonnes, which means a burn of 2.19 km/s past staging.

So if EUS launches with only Orion (26 tonnes), it will have a staging mass of 16.04 + 26 + 129 tonnes and reach LEO with an m₁ of 105.3 tonnes, of which 63 tonnes is excess propellant. If you do EOR and already have your extra cargo loitering in LEO, what can you send to TLI with that 63 tonnes of propellant? Getting to TLI requires a propellant fraction of 50.821% at 460.1 seconds, so your maximum mass out of TLI is 123.96 tonnes. Hurrah! You can now co-manifest (with a separate LEO launch) up to 18.66 whole tonnes! Which is less than Orion's carrying capacity and less than FH can send to TLI independently.

EUS is stupid.

Because SLS is stupid.

 

 

[YNM]

2 hours ago, tater said:

What 40t cargo do they have, and where is it going?

I wasn't aware of any missions even penciled in for anything other than Artemis.

An HLS system as a cargo makes little sense, as that would involve cryos, and they'd need to launch Orion very rapidly afterwards.

[...]

? I wasn't aware Block 2 was even on the table as a thing any time in the next several years.

If they're still peddling the lunar surface outpost then 40 tonnes from SLS B1b might actually be a conservative amount. But lord knows how far away those are. SLS B2 would be needed if they're serious about putting permanent habitation down, plus stuff like ISRU, maybe trying to go to the redder orb as well.

If it's just Gateway station then even the Block 1 Artemis is overkill - plus commercial launchers would be able to do this soon after (we have FH and DIVH already, maybe if Vulcan Heavy could be accelerated it'd soon amount to 3, plus there's SpX's Starship + Booster a little further ahead) so yeah if Gateway is all they're ever planning then it's absolutely unnecessary. (Zvezda is 23 tonnes, JEM is 24 tonnes, so even the largest modules have good safety margin with SLS Block 1, and other launchers - likely FH or Vulcan Heavy - can launch them, just.)

Which is why I hope it doesn't stop at Gateway only. But that'll take a while to settle...

Edited January 29, 2021 by YNM

[tater]

The current issue is cost vs capability.

Unless Block 1b can accomplish some useful mission, I'm not sure what the point of it is.

What 40t cargo exists? The Dynetics lander? Parts of the National Team lander? Can they sit around waiting on a second SLS launch within a few weeks? Is it worth 2 billion or more (not even counting B1B dev costs) to send such a cargo when they might be sent in 3 parts otherwise at a small fraction of the cost?

[YNM]

29 minutes ago, tater said:

What 40t cargo exists? The Dynetics lander? Parts of the National Team lander? Can they sit around waiting on a second SLS launch within a few weeks? Is it worth 2 billion or more (not even counting B1B dev costs) to send such a cargo when they might be sent in 3 parts otherwise at a small fraction of the cost?

Well idk, imagining like a few rovers and permanent habs and stuff for the surface, which would be somewhat sensible to be put on SLS with EUS thanks to the volume.

But yeah like they'd probably be in production only once we have an alternative from the private US sector as well. If the first SLS were off the ground a few years ago we might be looking for them sooner, but alas we aren't.

[tater]

33 minutes ago, YNM said:

Well idk, imagining like a few rovers and permanent habs and stuff for the surface, which would be somewhat sensible to be put on SLS with EUS thanks to the volume.

But yeah like they'd probably be in production only once we have an alternative from the private US sector as well. If the first SLS were off the ground a few years ago we might be looking for them sooner, but alas we aren't.

Of the 40t sent towards the Moon. About 6 tons needs to be spent to get it to LLO (assuming an I_sp of 465s)

With an Apollo like dv budget, that means maybe around 21t could be landed on the surface including the dry mass of the spacecraft (not bad). So if the goal was landing a hab and rover, such a LV might be a decent choice. The program would of course still need a crew vehicle and crew lander on top of that, so the rover and hab need to have decent longevity, and have to be landed in such a way that follow-on landers don;t harm them with ejecta from their engine plume regolith interaction ,

So that is a use case for a cargo SLS, essentially direct to the lunar surface, to preposition mission elements on the surface.

Maybe in such a case, the crew lander could be a bare bones affair, even less capable in terms of living space, etc, than the Apollo LEM... Oh, wait, it has to be substantially more capable, because Orion stinks. Why? Because NRHO means that the lander needs to be bigger (NRHO and back with more crew, so more props), and give the required abort capability, safety is not a few hours away, even with phasing, it's possibly days away because of the eccentric NRHO. Hence more stores/consumables.

So to get to a decent cargo use case we need...

1. the hab/rover idea above as the cargo.

2. A B1b with the excess capacity used so that Orion can go to LLO (because it pretty much takes all of what SLS can do to get that bloated capsule into a useful orbit).

3. Some commercial launch(es)to get a lander pre-positioned in LLO.

#3 could then be a much less substantial lander. The 17.1t to LLO (per @sevenperforce) with FH would do nicely. Make something akin to the LEM as a sortie lander. The crew does EVA to the pre-positioned hab.

 

Mars DRMs had similar habs massing ~17t I think (landed).

(I believe that is a 2 deck, 8.4m diameter hab)

Instead of the MAV sent ahead, a tiny lander/ascent vehicle is used, and the hab is sent ahead.

Edited January 29, 2021 by tater

[tater]

The above would have been a far better pitch by Boeing than what they did pitch, or the current landers (except Starship, which is a descent stage, ascent stage, and vast hab).

Huge, expensive launch (get some of those SLS dollars!) of what is in effect a trivial tube with some engines, mostly empty space.

Huge, expensive launch of an improved SLS (read: more expensive, hence more to Boeing) with Orion/EUS.

Commercial launch of a far simpler small lander that is just a taxi (this is easily possible since the LEM would fit and could be sent to LLO by FH).

Edited January 29, 2021 by tater

[RCgothic]

5 hours ago, sevenperforce said:

Yep.

Let's do the gorram math then. SLS Block 1 with ICPS can send 27 tonnes to TLI. Orion is 26.52 tonnes at TLI injection so that's the limit of ICPS.

Let's say FH can throw 23 tonnes to TLI, which is probably conservative. 

It costs 730 m/s of dV to get to low lunar orbit and 430 m/s of dV to get to NRHO. With 23 tonnes of injection mass and a 300 s hypergolic insertion stage, it takes 5.1 tonnes of propellant to reach LLO and 3.1 tonnes of propellant to reach NRHO. Borrowing mass fractions from the Delta-K (950 kg empty & 6004 kg props =  15.8% stage mass to prop mass), that means a stage mass of approximately 490 kg for the NRHO insertion stage and 806 kg for the LLO insertion stage. These numbers are conservative because you don't need NEARLY this much thrust for cislunar burns, so your engine mass is going to be lower (300 s is the specific impulse of small pressure-fed Draco thrusters so this is also conservative). So FH can send at least 17.1 tonnes to LLO and at least 19.4 tonnes to NRHO. This is dramatically more than can be co-manifested with EUS and Orion **plus** it arrives at the destination without borrowing any dV from Orion.

 

But wait, there's more!

What if EUS was used in an Earth Orbit Rendezvous architecture?

Orion's service module carries 8.6 tonnes of propellant. Assuming it goes to NRHO, it needs to return itself to Earth entry interface, which costs 410 m/s of dV. Orion's dry mass is (26.52 - 8.6) 17.92 tonnes, so getting back to an Earth entry from NRO is going to cost it 2.54 tonnes of propellant at 316 seconds of specific impulse. Getting from TLI to NRHO costs 430 m/s which is a propellant fraction of 13%. This means the most Orion could actually deliver to NRHO while still retaining enough propellant for return (with NO margin) would be 20.1 tonnes. That's a whole half-tonne more than if you just sent your cargo direct to TLI on FH with an insertion stage!

But hold on. TLI costs 3.2 km/s. The ICPS will have a dry mass of 3.49 tonnes, of which the engine is 301 kg. If the ICPS tankage is 3.189 tonnes to  27.22 tonnes of propellant (11.72% of prop), then the EUS's 129 tonnes of prop mass should correspond to roughly 15.12 tonnes of tankage plus 230 kg*4 = 920 kg of engines for a dry mass of 16.04 tonnes. If EUS can send 40 tonnes to TLI at 460.1 s, then its m₁ would be 40 + 16.04 tonnes which gives an m₀ of 113.95 tonnes in LEO or 57.91 tonnes of propellant in LEO. Tracing the calculations backwards, we know that the staging mass of EUS + 40-tonnes-payload = 185.04 tonnes, which means a burn of 2.19 km/s past staging.

So if EUS launches with only Orion (26 tonnes), it will have a staging mass of 16.04 + 26 + 129 tonnes and reach LEO with an m₁ of 105.3 tonnes, of which 63 tonnes is excess propellant. If you do EOR and already have your extra cargo loitering in LEO, what can you send to TLI with that 63 tonnes of propellant? Getting to TLI requires a propellant fraction of 50.821% at 460.1 seconds, so your maximum mass out of TLI is 123.96 tonnes. Hurrah! You can now co-manifest (with a separate LEO launch) up to 18.66 whole tonnes! Which is less than Orion's carrying capacity and less than FH can send to TLI independently.

EUS is stupid.

Because SLS is stupid.

 

 

And if we're talking about EOR, Falcon Heavy can send 32t if it meets that cargo in orbit.

And 32t is conveniently 2x reusable F9 launches. Which might be, say, 1) Dragon with the trunk used as a mission endurance module, and 2) An LLO insertion/return stage based on Dragon XL.

[YNM]

9 hours ago, tater said:

So that is a use case for a cargo SLS, essentially direct to the lunar surface, to preposition mission elements on the surface.

Maybe in such a case, the crew lander could be a bare bones affair, even less capable in terms of living space, etc, than the Apollo LEM... Oh, wait, it has to be substantially more capable, because Orion stinks. Why? Because NRHO means that the lander needs to be bigger (NRHO and back with more crew, so more props), and give the required abort capability, safety is not a few hours away, even with phasing, it's possibly days away because of the eccentric NRHO. Hence more stores/consumables.

So to get to a decent cargo use case we need...

1. the hab/rover idea above as the cargo.

2. A B1b with the excess capacity used so that Orion can go to LLO (because it pretty much takes all of what SLS can do to get that bloated capsule into a useful orbit).

3. Some commercial launch(es)to get a lander pre-positioned in LLO.

#3 could then be a much less substantial lander. The 17.1t to LLO (per @sevenperforce) with FH would do nicely. Make something akin to the LEM as a sortie lander. The crew does EVA to the pre-positioned hab.

Or Block 2. Like I said, sending stuff to the surface would only really be in grasp once something with the lift capability of SLS B2 exist. B1b would be a bit of collecting rags together still.

The problem really is that we've taken all of this forever since Shuttle ended, when using Shuttle-derrived stuff would still makes sense. These days something from a clean sheet design would be as attractive as a Shuttle-derrived things. If anything methalox is going to be the rage when SLS enters regular service...

Edited January 29, 2021 by YNM

[tater]

Block 2 is not really much of an improvement. 46t to TLI vs 40?

The original issue with SLS still stands. It was not designed to accomplish any specific mission.

It's completely fine to make a "jack of all trades" vehicle, but that means it needs to be over-capable so that it can achieve plausible mission goals. Any such vehicle can either accomplish those goals with cadence, or with capability. The cost of SLS was always such that cadence could never be a thing. If lunar operations are on the table as a possible BLEO mission for any concept SLS, then it needed to have maybe 60-70t to TLI as a minimum capability. Anything less than that is effectively useless.

[tater]

 

[Mitchz95]

"Inspections showed the core stage hardware, including its engines, and the B-2 test stand are in excellent condition after the first hot fire test, and no major repairs are needed to prepare for a second hot fire test"

How do you go from MCF (major component failure) to "no repairs needed"? Am I misunderstanding the term?

And wasn't the original test supposed to run for six minutes? Why down to four now?

[RealKerbal3x]

16 minutes ago, Mitchz95 said:

How do you go from MCF (major component failure) to "no repairs needed"? Am I misunderstanding the term?

In this case, MCF just referred to a loss of one leg of redundancy. It's quite misleading.

[tater]

Meanwhile:

 

The SRBs are in 8 pieces. The nose and avionics pieces are stacked above. Then there are the 5 propellant segmens, the bottom one has the nozzle, and a little skirt around that with the sep motors.

Assuming that the above 2 segments are each ~1/6 the cost (the avionics has to cost more than a tube of propellant), each of the above nose cones costs about 78.5 million dollars.

[Mitchz95]

 

Edited February 8, 2021 by Mitchz95

[RealKerbal3x]

Depot.

We can say depot now!

Edited February 9, 2021 by RealKerbal3x

[tater]

Useful post by Steven Pietrobon on NSF regarding simulations of SLS blocks and mentions specific NASA claims as well. His sims: http://www.sworld.com.au/steven/space/sls/

He says that NASA says SLS B1b with Orion is 38t to TLI, and cargo alone 42t.

Useful because the only difference there is presumably the huge mass of the LES, and whatever trajectory changes are required for crew missions such that abort is possible. The latter is something I know about in an academic sense, but I tend to forget about when discussing SLS.

So we have a 9.5% performance hit for including Orion.

 

[RCgothic]

On Jan 25th it sounds like SLS definitively lost Clipper:

 

 

[tater]

 

Given the test is in 3 days, and they probably take 3 days just to set an agenda for a meeting... I imagine the second Green Run slips.

[RyanRising]

I know this absolutely, positively will not and cannot happen, for many, many reasons. But what sort of rocket would it take to send Orion, an appropriately upgraded service module, and a four-person lander on a lunar landing mission single-launch? Expense, debris, and politics aside.