[New] Space Launch System / Orion Discussion Thread

[tater]

46 minutes ago, jadebenn said:

Those are programmatic minimums. In that same thread on NSF, someone dug up the ESD requirements, which, while incomplete, paint a much different picture.

Cool, that link doesn't work for me. Probably needs a redirect from a parent page.

Odd that NASA would accept 1:75 though. Seems pretty rough, glad to see SLS/Orion is ahead of that.

[RCgothic]

They do like to milk the "SLS is the most powerful rocket ever" propaganda. It's not.

SLS will, assuming Superheavy doesn't fly with at least 14 engines before next February, briefly hold the title of most thrust at liftoff of any rocket ever.

Most powerful (total impulse) is still Saturn V.  60t total to TLI can't be argued with until Block 2, if that ever happens.

Most powerful (instantaneous power) is probably also Saturn V.  Thrust times velocity, I'm pretty sure S-IC is producing more power at centre engine cut off and outboard-engine cutoff than SLS is at BECO. SRBs have a vaguely decaying thrust profile.

And Superheavy is rapidly arriving to take all of these titles for itself if SLS doesn't hurry up.

Edited March 19, 2021 by RCgothic

[tater]

4 minutes ago, RCgothic said:

Most powerful (total impulse) is still Saturn V.  60t total to TLI can't be argued with until Block 2, if that ever happens.

Do they claim 60t to TLI on Block 2? With Orion? (cargo TLI mass is better than with Orion presumably because of LES mass combined with a different trajectory compatible with safe crew abort)

Heck, that's almost useful... not sure what the cutoff is for a lander that also gets stuck with the LOI burn in LLO. I want to say I figured it was closer to 65-70t for the whole stack at TLI.

Edited March 19, 2021 by tater

[RCgothic]

11 minutes ago, tater said:

Do they claim 60t to TLI on Block 2? With Orion? (cargo TLI mass is better than with Orion presumably because of LES mass combined with a different trajectory compatible with safe crew abort)

Heck, that's almost useful... not sure what the cutoff is for a lander that also gets stuck with the LOI burn in LLO. I want to say I figured it was closer to 65-70t for the whole stack at TLI.

That'd be SLS ~48t payload to TLI plus ~15t EUS after burnout ~=63t total.

Saturn V was ~60t to TLI including S-IVB.

 

Of course Saturn V sent over 48t payload to TLI as well, so in terms of useful work done it'd still be a tossup. It's just that S-IVB is lighter. Hence the argument.

Edited March 19, 2021 by RCgothic

[RyanRising]

4 hours ago, sevenperforce said:

Total first-stage thrust at liftoff:

[snip]

• Saturn V: 35.1 MN
• SLS: 36.6 MN
• N1: 45.4 MN

[snip]

 

1 hour ago, RCgothic said:

They do like to milk the "SLS is the most powerful rocket ever" propaganda. It's not.

SLS will, assuming Superheavy doesn't fly with at least 14 engines before next February, briefly hold the title of most thrust at liftoff of any rocket ever.

Most powerful (total impulse) is still Saturn V.  60t total to TLI can't be argued with until Block 2, if that ever happens.

Most powerful (instantaneous power) is probably also Saturn V.  Thrust times velocity, I'm pretty sure S-IC is producing more power at centre engine cut off and outboard-engine cutoff than SLS is at BECO. SRBs have a vaguely decaying thrust profile.

And Superheavy is rapidly arriving to take all of these titles for itself if SLS doesn't hurry up.

Pretty sure the N1 lifted off a few times, so they can't honestly claim SLS has the highest thrust of any rocket ever even if it does fly. They sure can claim it's the highest thrust flying if it does fly before Superheavy, though.

 

1 hour ago, RCgothic said:

That'd be SLS ~48t payload to TLI plus ~15t EUS after burnout ~=63t total.

Saturn V was ~60t to TLI including S-IVB.

 

Of course Saturn V sent over 48t payload to TLI as well, so in terms of useful work done it'd still be a tossup. It's just that S-IVB is lighter. Hence the argument.

(sorry for double-post, dunno how to insert a quote into a post I'm editing)

Why is the EUS heavier than the S-IVB? 4 RL-10s > 1 J-2? Or did the S-IVB have a common dome where the EUS doesn't. and the insulation required for that is lighter?

[sevenperforce]

23 minutes ago, RyanRising said:

Pretty sure the N1 lifted off a few times, so they can't honestly claim SLS has the highest thrust of any rocket ever even if it does fly. They sure can claim it's the highest thrust flying if it does fly before Superheavy, though.

Yeah, that's what I was going to say. Obviously the N1 didn't get very high but it certainly launched, and it made both Saturn V and the SLS look wimpy.

24 minutes ago, RyanRising said:

Why is the EUS heavier than the S-IVB? 4 RL-10s > 1 J-2? Or did the S-IVB have a common dome where the EUS doesn't. and the insulation required for that is lighter?

The RL10C-3 is just 230 kg; four of those mass about half what the J-2 massed. I suspect @RCgothic meant that the wet mass of the S-IVB was lower than the wet mass of the EUS. The EUS is going to carry around 129 tonnes of propellant; the S-IVB only carried 109 tonnes of propellant.

I suspected the Saturn V's second stage did much more to get the S-IVB nearly to orbit than the SLS core will do to get the EUS nearly to orbit. I don't know what the dV deficits are, though.

[RCgothic]

Nope, I mean the S-IVB at burnout weighs less than EUS at burnout. 

[tater]

Wiki says Block 2 is 45t payload mass to TLI (presumably not counting the dry mass of EUS).

EUS mass could be counted assuming the payload included residual props, particularly if EUS got some ACES-like tech (IVF) and was used for LOI.

[RCgothic]

Well Wikipedia also defines Saturn V as "most powerful (total impulse)", so I'm being a little generous to SLS by considering a definition of total impulse to be "total mass accelerated to final velocity, multiplied by velocity", thus including its heavier final stage and saying "arguably", because stages without fuel don't count as useful payload, as rightly pointed out.

But if block 5 can only manage 45t payload to TLI and EUS weighs around ~15.6t at burnout, that's just 60.6t.

Saturn V managed 48.5t to TLI and S-IVB weighs 13.5t, then that's about 62t, so SLS won't win even on this metric unless it finds some extra payload somewhere.

 

Bottom lines:

Thrust on the pad is not power.

SLS will probably not have the highest instantaneous power.

SLS probably won't have most payload to TLI.

SLS probably won't have highest total mass (total impulse) to TLI.

SLS will not have most mass/payload to LEO.

[Scotius]

I'm a simple man. What i know is:

Saturn V did her job of delivering her payload to the destination and back. Without the crutch of SRB's strapped to her.

SLS can't do the same even with additional thrust of solid boosters.

Do we even need to compare the two?

[RealKerbal3x]

41 minutes ago, Scotius said:

I'm a simple man. What i know is:

Saturn V did her job of delivering her payload to the destination and back. Without the crutch of SRB's strapped to her.

SLS can't do the same even with additional thrust of solid boosters.

Do we even need to compare the two?

Heck, SLS can't even lift off without two of the world's largest boom sticks.

[kerbiloid]

SLS feeds Thiokol, Saturn didn't.

[tater]

20 hours ago, jadebenn said:

Those are programmatic minimums. In that same thread on NSF, someone dug up the ESD requirements, which, while incomplete, paint a much different picture.

Hey, the link works now. Dunno what my issue was before.

Interesting.

It's odd that they list a number of PRAs for Shuttle, and the numbers are about like the actual LOC rate, but I recall seeing retroactive studies of Shuttle risk that put it an order of magnitude higher for the first... 20 or so launches? (sorry, from memory). Like 1:9 LOC risk, that level, they just lucked out.

Orion seems pretty good at least, though we'll have to see how the new TPS does with Artemis I (that changed since the boilerplate mission flown on DIVH, right?).

[RCgothic]

21 hours ago, RCgothic said:

They do like to milk the "SLS is the most powerful rocket ever" propaganda. It's not.

SLS will, assuming Superheavy doesn't fly with at least 14 engines before next February, briefly hold the title of most thrust at liftoff of any rocket ever.

Haha, wait, N1 had massively more thrust than SLS at liftoff!

Nope, genuinely can't think of a metric under which SLS is most powerful without some sort of qualification.

[insert_name]

2 minutes ago, RCgothic said:

Haha, wait, N1 had massively more thrust than SLS at liftoff!

Nope, genuinely can't think of a metric under which SLS is most powerful without some sort of qualification.

political willpower?

[wumpus]

1 hour ago, RCgothic said:

Haha, wait, N1 had massively more thrust than SLS at liftoff!

Nope, genuinely can't think of a metric under which SLS is most powerful without some sort of qualification.

Assuming the boosters have more thrust than the shuttle's (presumably that's what the extra segments are for), they will be the most powerful engines ever launched.  SLS in total won't have any such achievements, other than most expensive rocket ever.

[tater]

The SLS 5 segment SRBS have more thrust, and higher Isp than the Shuttle SRBs.

 

[sevenperforce]

On 3/20/2021 at 2:37 PM, RCgothic said:

Haha, wait, N1 had massively more thrust than SLS at liftoff!

Nope, genuinely can't think of a metric under which SLS is most powerful without some sort of qualification.

If SLS launches before Superheavy then it will briefly have the highest thrust of any rocket launched from US soil.

SLS will be the highest-thrust hydrogen first stage ever (it's 22% higher-thrust than the Energia core). So I guess that's impressive, for what it's worth. And of course they do have the thrustiest boomsticks of all time, as pointed out by @tater and @wumpus and @RealKerbal3x.  I suppose you could say that SLS has all the best parts but it's a situation where the whole is less than the sum of the parts.

On 3/20/2021 at 5:37 AM, Scotius said:

Saturn V did her job of delivering her payload to the destination and back. Without the crutch of SRB's strapped to her.

SLS can't do the same even with additional thrust of solid boosters.

A hydrolox stage-and-a-half design is just an inherently crippling design. 

[tater]

I ended up getting into this a little at NSF, though I had written this first, and forgot to hit reply, lol.

What useful crewed mission goal can be achieved with an SLS/Orion flight? Heck, even multiple flights in a cadence that can actually be demonstrated as likely (in which case boil off clearly matters)?

I don't mean an SLS/Orion flight, plus a large, indeterminate number of commercial launches, just SLS.

Anyone paying attention knows the answer already—there are no useful crewed mission goals that can be accomplished by SLS/Orion alone. Not Block 1, not Block 1B, not the notional Block 2. The Orion part is important, BTW.

This is the fundamental problem with it, all the other complaints are secondary (even if many/most of them are entirely valid). If the purpose of SLS/Orion is BLEO human spaceflight broadly speaking, what are useful BLEO human spaceflight missions, and what does SLS/Orion do to accomplish them?

I posted this even at NSF, and the SLS proponents (one of them in this thread) answer other questions, but not that one (the only one that matters, IMHO).

If you must assume many secondary flights of different launch vehicles to create someplace for SLS/Orion to go (Gateway), then shouldn't the system have been optimized from the start to most efficiently deliver crew to distant lunar orbit? In that use case, it's is a transit vehicle like the commercial crew vehicles. It gets people to Gateway, then Gateway supports them. Any excess capability/mass is wasted.

In short, could an SLS-like system have been optimized for just getting a CSM to NRHO, and could it be done with a reasonable cadence and cost? What is the minimum mass CM required to comfortably (or as comfortably as Orion) get 4 humans to NRHO, and back? No excess capacity is required. Could such a capsule maybe cost less than $900,000,000 each? Could a different LV have accomplished this goal?

The Apollo CSM was 28,800kg, slightly more massive than Orion CSM. None the less it was capable of doing the LOI burn for a 45.2t stack at LLO, then sending the CM home via TEI. If the mission goal was NOT to do this, but only to get to a distant lunar orbit, you could have a larger volume capsule (like Orion is), and a smaller SM, since it only needs to do LOI and TEI at a distant lunar orbit, and only for itself. It strikes me this must be possible for less than the Orion CSM costs, and more importantly, for substantially less mass than the Apollo CSM's 28t. The Apollo capsule was ~5550kg. The RT dv for NRHO is only ~900 m/s. A 7 ton CSM (dry) could mass only 10t wet and get to NRHO and back, any additional capacity a LV would obviously be used. Vulcan can do ~12t to TLI. FHe can do over 20. NG could easily do it as well. If distributed launch is permitted, it becomes easier still. Even Atlas V can play. 4 crew-rated LVs, any 2 launches still an order of magnitude cheaper than 1 SLS launch.

In short, around 3.2 billion dollars a flight is not reasonable, it's just not—it would be if it was to land on the Moon, IMO, but not to NOT land on the Moon. All SLS can do is taxi people to a useless orbit.

And yes, it is ~3.2B$/flight.

2 SRBs are just shy of a billion alone, every flight. SSMEs are half a billion alone per flight. ICPS is a couple hundred million. Unless the entire core stage, interstages, etc are somehow much less than 250M$ combined, every SLS is 2B$. Maybe in late production that unit price drops below 2B to between 1.5B$, and 2B$. Pick a number, in there, whatever.

There is no SLS flight without Orion, however, so we need to add Orion. Orion is set to be ~900M$ for Artemis III through Artemis V. The first 2 are more, and maybe after V they are cheaper by some amount. The third ESM was contracted for 250M€ (~300M$). So 2B$ for each SLS, and 1.2B$ for each CSM coming to 3.2B$/flight.  At some point perhaps SLS costs drop closer to 1.8B$ and we can get this down as low as 3B$/flight. Yippee.

Edited March 22, 2021 by tater

[wumpus]

On 3/22/2021 at 11:14 AM, sevenperforce said:

thrustiest boomsticks of all time, as pointed out by @tater and @wumpus and @RealKerbal3x.  

Thrustiest boomsticks that ever launched.  AJ-260 [edited] and its 2.6 MN thrust weeps on Earth.

[further edit: 2.6MN needed a nozzle which was blown off during the test].

Edited March 23, 2021 by wumpus
see thread

[sevenperforce]

14 minutes ago, wumpus said:

Thrustiest boomsticks that ever launched.  AJ-60 and its 1.7MN thrust weeps on Earth.

Do you mean AJ-260?

 

[wumpus]

4 minutes ago, sevenperforce said:

Do you mean AJ-260?

 

That must be it.  Sound isn't working and youtube-cc must have lopped off some of Scott Manley's accent.  I googled it and it existed, but didn't check closely enough.

[tater]

I went off on a tangent above, what I mean regarding an alternate "SLS/Orion" was that if the goal is NOT to ever do single launch, useful human lunar missions (landing), but instead to taxi humans to a distant lunar orbit, then SLS should have been optimized to send a minimal human taxi to NRHO. That vehicle might mass as little as 10t, or it could be a little bigger with more comfort (an orbital module designed to serially add to Gateway, perhaps).

This would lead to a design for 10-20t to TLI, vs 26t to 45t to TLI. A substantially smaller vehicle, with substantially smaller costs.

[sevenperforce]

1 hour ago, tater said:

I went off on a tangent above, what I mean regarding an alternate "SLS/Orion" was that if the goal is NOT to ever do single launch, useful human lunar missions (landing), but instead to taxi humans to a distant lunar orbit, then SLS should have been optimized to send a minimal human taxi to NRHO. That vehicle might mass as little as 10t, or it could be a little bigger with more comfort (an orbital module designed to serially add to Gateway, perhaps).

This would lead to a design for 10-20t to TLI, vs 26t to 45t to TLI. A substantially smaller vehicle, with substantially smaller costs.

This is why I still pine for Jupiter DIRECT. They could have done a much lighter Orion/MPCV to service the ISS with a service module large enough to fill the role of the OMS engines on the Shuttle. Same launch profile as the Shuttle (perhaps only with two SSMEs per launch), with the core ending up in an atmosphere-crossing orbit and the service module providing the remaining 300 m/s or so for LEO.

Add an ICPS-sized second stage with everything else exactly the same, and Orion could co-manifest new modules to the ISS using the old Apollo flip-and-dock.

Using an ICPS-sized second stage (and, again, NO other LV upgrades) and an upgraded heat shield, you can test a lunar free-return by using Orion's SM to complete TLI. 

With a slightly larger second stage and perhaps an extra SSME, you can use this Orion Lite with the upgraded heat shield as a minimal human taxi to NRHO. On a vehicle that's almost totally Shuttle-derived, without all the dev costs that SLS has incurred over the years.

[tater]

Yeah, DIRECT was great.

Pick a set of mission goals, then design something that can accomplish those mission goals.

A Jack of all trades approach (master of none )I am actually fine with—but SLS is definitively not a JoaT, since it is not really a Jack of any trade. To be a multi-purpose system, it would have to be capable of multiple mission profiles.