NASA SLS/Orion/Payloads

[StrandedonEarth]

8 minutes ago, Starman4308 said:

I'd probably go for large kerolox boosters

F9s?

[jadebenn]

7 minutes ago, StrandedonEarth said:

F9s?

If they ever get to Block 2, they'll have to switch from SRBs anyway if they want to meet their payload target. Would be nice to see this a variant of this proposal revived:

I wouldn't hold my breath, though. Even if the other SLS variants have a long and successful career, I have severe doubts Block 2 will ever fly.

Edited April 11, 2019 by jadebenn

[tater]

SLS has had F-1B side boosters proposed.

The whole stage and a half thing is sorta bizarre.

[Starman4308]

9 minutes ago, StrandedonEarth said:

F9s?

While there is a very amusing KSP video to that effect, I was thinking more along the lines of Pyrios boosters, powered by simplified F-1B engines.

16 minutes ago, jadebenn said:

It's no conspiracy. It's politics. Back when Obama was pushing ARM, NASA made the decision to basically do what you're saying: 'skip' Block I in favor of Block IB. Unfortunately, they were told to keep EM-1, so they compromised on doing one Block I mission then switching over (which IMO is the worst of both worlds, but whatever).

Five years later, and thanks to this new aggressive schedule, it looks like Block I is going to be the real workhorse of the fleet, and Block IB's future is uncertain. A complete reversal over just five years! Seems like a lot of time, but it's really not that long at all when you're dealing with literal rocket science.

This is why a lot of people bang on about having clearly-defined mission goals: because then you don't have to deal with a rocket constantly in flux. But the politics don't let you, because if you specifically build a moon rocket and the next guy doesn't want to go to the moon, welp, there goes your moon rocket. Thus NASA overbuilds generalist rockets that can be adapted to fit the politics, because it's the only way they can get anything built at all.

 

I see a few issues with that view of things:

1) SHLVs are not generalist vehicles. The commercial sector has generalist vehicles capable of a very wide variety of missions, ranging from COTS/Commercial Crew, to deep-space probes, to mundane weather/communications/navigation satellites well handled. The only thing you need SHLVs for is to make super-heavy missions like manned BEO exploration possible with a minimum of assembly.

2) The SLS is underbuilt for most conceivable super-heavy missions. It can't do a single-stack lunar landing, meaning assembly is required... and if you admit "some assembly necessary", then you run into schedule/tempo issues, and running the mission with commercial LVs starts to look more attractive. An Ares V would've been a semi-decent option: stupidly expensive, but big enough for single-stack lunar landing, giving it a guaranteed SHLV niche, and breathing room to be used for other missions like superheavy probes or assembling a Mars vehicle. SLS sits right in that awkward zone where it's too big for run-of-the-mill tasks, but not quite big enough to have a guaranteed niche.

3) An expendable SHLV was likely a decent choice in the Bush Jr/Obama era, when options commercial HLVs were fairly limited and expensive. Unfortunately, instead of either pressing through on Constellation or cancelling it outright, we got a compromise that mostly just serves to funnel money to Shuttle-era contractors without being a good solution to anything.

[jadebenn]

Folks, let me elucidate you all on the sad story of a project known as DIRECT. The idea was simple, and may sound familiar: build a new heavy lifter out of old shuttle parts to minimize downtime in-between the shuttle transition. It was basically an engineer revolt from inside NASA against the (ill-fated) Ares I and V rockets of the Constellation program. DIRECT is similar to SLS, and in many ways was the program's "father," but it was distinct from the end-product in a number of ways.

The primary motivation behind DIRECT was to close the launch gap. The shuttles were going. It had already been decided and no-one wanted to revisit that. However, the promise of DIRECT was that the majority of the shuttle workforce and infrastructure could be retained. This is a big deal: any more than a few years downtime and a large amount of that knowledge just goes away as people retire or move onto new jobs. DIRECT was supposed to prevent this. Here's how:

This rocket, known as Jupiter, is basically just a shuttle rocket, minus the... y'know, shuttle. Very little modification. The biggest change would be moving the three SSMEs to the bottom of the external tank and flattening its top. The resulting rocket would be highly capable, with a payload capacity of about 70 mT to LEO per launch. Hey, wait a minute! Doesn't that number sound familiar? Don't worry, I'm getting to that.

When the Obama administration canceled Constellation, NASA and Congress freaked out. Eventually, with the help of the DIRECT people, a compromise was reached. Orion was "un-cancelled" and Congress wrote the goals of the DIRECT program (more-or-less) into law. They called the resulting rocket the Space Launch System, or SLS for short.

Feeling satisfied, DIRECT disbanded. They didn't get everything they wanted, but they felt pretty good about this new "SLS" thing. After all, it seemed to follow the principles they had set out that would allow maximum commonality with shuttle equipment and minimize the gap between the shuttle program and its successor. What could go wrong?

Well, uh, NASA management interpreted this act far differently than they intended, and the result was essentially a fusion between the original vision for DIRECT and the canceled Ares V. Unfortunately this brought about the exact situation DIRECT was meant to avoid, and well... let's just say that most ex-DIRECT people you'll find won't have very nice things to say about the SLS.

Edited April 11, 2019 by jadebenn

[Starman4308]

If you really want a Shuttle-derived vehicle with minimal modifications, you would have gone with Shuttle-C. The DIRECT proposal was probably doomed from the start: you're making enough modifications to the baseline design that you would have seen serious modification creep courtesy of politicians... like we got with the SLS. "Why don't we just go with 5-segment boosters? Why don't we go with 4 engines? Why not add an upper stage?". All of which sound reasonable individually, but were guaranteed to funnel more and more money to developing the rocket with no need to actually produce results. With Shuttle-C, the only modification is replacing the Orbiter with what amounts to a tube. Same fuel feed, minimal pad modifications, etc.

[jadebenn]

Issue with Shuttle-C was being saddled with that side-mounted design. Fine for cargo, but not something I'd want to stick with for manned considering how conclusively the shuttle program showed that to be a bad idea.

I mean, it'd still be safer than shuttle, because at least then you can stick an LES on the capsule, but long-term, moving back to top-mounted was definitely the way to go.

I don't actively dislike the SLS like a lot of people in the space community do, but I can especially understand why the DIRECT people loathe it. Their idea was compromised the second NASA decided to switch to 5-segment SRBs.

That set off a domino effect, where then they needed to strengthen the core stage, and then since they were already re-designing the core stage they may as well stretch it, and oh hey let's add another engine to the core as well while we're doing that, and so-on and so-forth until the resultant product was barely shuttle-derived at all. Thus, SLS failed at the job the DIRECT people wanted it to do, and as a consequence it burnt a lot of them on NASA permanently.

Edited April 11, 2019 by jadebenn

[tater]

1 hour ago, jadebenn said:

This is why a lot of people bang on about having clearly-defined mission goals: because then you don't have to deal with a rocket constantly in flux. But the politics don't let you, because if you specifically build a moon rocket and the next guy doesn't want to go to the moon, welp, there goes your moon rocket. Thus NASA overbuilds generalist rockets that can be adapted to fit the politics, because it's the only way they can get anything built at all.

Except of course SLS is not overbuilt, it's underbuilt. Launch cadence is not ever going to change, so unless it can do "place_your_mission_here" in 1 launch, it's not going to happen.

The Moon should stay the goal, frankly, Mars was always a stupid plan, because NASA never had the resources to do a human Mars mission, nor will they. International partners like the Moon, because they can actually participate (since none of them spend serious money on space at all). The Moon is also actually possible, unlike Mars (sorry Zubrin, et al, it's just not going to happen).

36 minutes ago, jadebenn said:

Well, uh, NASA management interpreted this act far differently than they intended, and the result was essentially a fusion between the original vision for DIRECT and the canceled Ares V. Unfortunately this brought about the exact situation DIRECT was meant to avoid, and well... let's just say that most ex-DIRECT people you'll find won't have very nice things to say about the SLS.

Yep. Direct was a decent idea. SLS... not so much.

[Starman4308]

5 minutes ago, jadebenn said:

Issue with Shuttle-C was being saddled with that side-mounted design. Fine for cargo, but not something I'd want to stick with for manned considering how conclusively the shuttle program showed it to be a bad idea.

I mean, it'd still be safer than shuttle, because at least then you can stick an LES on the capsule, but long-term, moving back to top-mounted was definitely the way to go.

The response to that would be "why human-rate it?" I've never seen a convincing reason why the people have to go up on the same can as the cargo. Human-rating the cargo can makes the cargo can more expensive, and putting people on the cargo can means putting humans closer to unnecessarily large quantities of highly energetic propellant and complicated LV. On top of that, an LEO taxi could be built on very well-proven commercial medium LVs, instead of needing a very low-flight-rate vehicle that's harder to ensure the reliability of.

We should have had Commercial Crew a long time ago.

[tater]

Direct also could have probably maintained a Shuttle cadence (assuming any payload existed). Unlike SLS.

[jadebenn]

1 hour ago, Starman4308 said:

I see a few issues with that view of things:

1) SHLVs are not generalist vehicles. The commercial sector has generalist vehicles capable of a very wide variety of missions, ranging from COTS/Commercial Crew, to deep-space probes, to mundane weather/communications/navigation satellites well handled. The only thing you need SHLVs for is to make super-heavy missions like manned BEO exploration possible with a minimum of assembly.

True. I should've clarified that they're generalist for the things NASA wanted to do. That was part of their political gambit. A president's a lot less likely to saddle you to LEO when your rocket's optimized for BEO, but at the same time you want it to be general enough that the cancellation of a specific goal (Do Mars! No, do asteroid! No, do Moon!) doesn't kill off the whole thing, like how the end of Apollo killed off the Saturn.

1 hour ago, Starman4308 said:

2) The SLS is underbuilt for most conceivable super-heavy missions. It can't do a single-stack lunar landing, meaning assembly is required... and if you admit "some assembly necessary", then you run into schedule/tempo issues, and running the mission with commercial LVs starts to look more attractive. An Ares V would've been a semi-decent option: stupidly expensive, but big enough for single-stack lunar landing, giving it a guaranteed SHLV niche, and breathing room to be used for other missions like superheavy probes or assembling a Mars vehicle. SLS sits right in that awkward zone where it's too big for run-of-the-mill tasks, but not quite big enough to have a guaranteed niche.

Again, I fundamentally agree with you here, but NASA was working with what they felt was the political reality. Too big, and the rocket gets cancelled if there's not a big enough goal to go along with it. Too small, and you're stuck in LEO for the foreseeable future. They went with the biggest rocket they felt they could get political approval for, which had to be unwieldy enough to stay out of LEO, but not too big for Congress to get sticker shock (that would come later, when they were already invested in the program).

1 hour ago, Starman4308 said:

 3) An expendable SHLV was likely a decent choice in the Bush Jr/Obama era, when options commercial HLVs were fairly limited and expensive. Unfortunately, instead of either pressing through on Constellation or cancelling it outright, we got a compromise that mostly just serves to funnel money to Shuttle-era contractors without being a good solution to anything.

I mean, Constellation really needed to go. Maybe there was something worth salvaging in the Ares V, but I cannot for the life of me understand why anyone thought the design of the Ares I was a good idea. Not only was it screwing up the other components of the plan (the modern Orion MPCV is still saddled with a lot of its legacy), it was just a really, really, dumb concept. Why use a solid for your first stage? They're great for ICBMs, or when you need a bit extra thrust, but they're terrible for manned flight, especially when they're on their own!

1 hour ago, tater said:

Yep. Direct was a decent idea. SLS... not so much.

I agree that the SLS is a flawed program, but I think it has its uses. My view of its utility mainly comes from my intense skepticism over commercial SHLV capability. I'd be happy to be proven wrong on this point, I assure you, but I just don't see it happening anywhere near as soon as they say it will. I'd rather not derail the thread by explaining every minute detail of why I feel this way, so let me just do the abridged version: Until we have a commercial SHLV flying, I do not feel comfortable cancelling the SLS. I'm fine with giving LEO over to the likes of SpaceX, but I don't think they're ready for BEO yet.

1 hour ago, Starman4308 said:

The response to that would be "why human-rate it?" I've never seen a convincing reason why the people have to go up on the same can as the cargo. Human-rating the cargo can makes the cargo can more expensive, and putting people on the cargo can means putting humans closer to unnecessarily large quantities of highly energetic propellant and complicated LV. On top of that, an LEO taxi could be built on very well-proven commercial medium LVs, instead of needing a very low-flight-rate vehicle that's harder to ensure the reliability of.

Eh, crew-cargo integration has its uses, mainly in massively simplifying mission planning. The main reason why it was so taboo to do for the shuttle was because in all honesty the shuttle was a deathtrap (comparatively, at the very least). It's different when you're not talking about putting the cargo in the same vehicle as the crew, just the same rocket. For example, putting the lunar lander on the Saturn V actually saved lives compared to launching separately.

But yeah. I see your point, and I can see the utility in a non-man-rated Shuttle-C coupled with a proto-COTS program. Though assuming current trends would've held, we still would've seen a large gap in human launch capability. But we wouldn't have lost the shuttle industrial base, so that's a pretty big deal.

1 hour ago, tater said:

Direct also could have probably maintained a Shuttle cadence (assuming any payload existed). Unlike SLS.

Eh. Maybe. It would've been a heckuva lot cheaper operationally and R&D than the SLS, but I think the launch cadence might've suffered just because it'd become harder to find things to do with it. We wouldn't be able to talk about the Moon missions right now, for example, and it'd be harder to justify in a world where commercial space can clearly handle LEO operations. I guess it really depends on how extensible the DIRECT platform would be. Could we get SLS-like payload figures without sacrificing the lower cost, perhaps by stacking enough upper stages, or through other incremental upgrades? Maybe. It's kind of pointless to discuss now that the STS industrial base is gone, though.

Edited April 11, 2019 by jadebenn

[Starman4308]

38 minutes ago, jadebenn said:

True. I should've clarified that they're generalist for the things NASA wanted to do. That was part of their political gambit. A president's a lot less likely to saddle you to LEO when your rocket's optimized for BEO, but at the same time you want it to be general enough that the cancellation of a specific goal (Do Mars! No, do asteroid! No, do Moon!) doesn't kill off the whole thing, like how the end of Apollo killed off the Saturn.

Again, I fundamentally agree with you here, but NASA was working with what they felt was political realities. Too big, and the rocket gets cancelled if there's not a big enough goal to go along with it. Too small, and you're stuck in LEO for the foreseeable future. They went with the biggest rocket they felt they could get political approval for, which had to be unwieldy enough to stay out of LEO, but not too big for Congress to get sticker shock (that would come later, when they were already invested in the program).

I mean, Constellation really needed to go. Maybe there was something worth salvaging in the Ares V, but I cannot for the life of me understand why anyone thought the design of the Ares I was a good idea. Not only was it screwing up the other components of the plan (the modern Orion MPCV is still saddled with a lot of its legacy), it was just a really, really, dumb concept. Why use a solid for your first stage? They're great for ICBMs, or when you need a bit extra thrust, but they're terrible for manned flight, especially when they're on their own!

I agree that the SLS is a flawed program, but I think it has its uses. My view of its utility mainly comes from my intense skepticism over commercial SHLV capability. I'd be happy to be proven wrong on this point, I assure you, but I just don't see it happening anywhere near as soon as they say it will. I'd rather not derail the thread by explaining every minute detail of why I feel this way, so let me just do the abridged version: Until we have a commercial SHLV flying, I do not feel comfortable cancelling the SLS. I'm fine with giving LEO over to the likes of SpaceX, but I don't think they're ready for BEO yet.

Eh, crew-cargo integration has its uses, mainly in massively simplifying mission planning. The main reason why it was so taboo to do for the shuttle was because in all honesty the shuttle was a deathtrap (comparatively, at the very least). It's different when you're not talking about putting the cargo in the same vehicle as the crew, just the same rocket. For example, putting the lunar lander on the Saturn V actually saved lives compared to launching separately.

But yeah. I see your point, and I can see the utility in a non-man-rated Shuttle-C coupled with a proto-COTS program. Though assuming current trends would've held, we still would've seen a large gap in human launch capability. But we wouldn't have lost the shuttle industrial base, so that's a pretty big deal.

Eh. Maybe. It would've been a heckuva lot cheaper operationally and R&D than the SLS, but I think the launch cadence might've suffered just because it'd become harder to find things to do with it. We wouldn't be able to talk about the Moon missions right now, for example, and it'd be harder to justify in a world where Commercial Space can clearly handle LEO operations. I guess it really depends on how extensible the DIRECT platform would be. Could we get SLS-like payload figures without sacrificing the lower cost, perhaps by stacking enough upper stages, or through other incremental upgrades? Maybe. It's kind of pointless to discuss now that the STS industrial base is gone, though.

First: I am seriously enjoying this conversation.There is a minimum of talking past each other.

The fundamental issue I see with SLS is that it can't practically do any of the big missions (e.g. ARM, lunar landings, Mars) without developing the technologies that obsolete the whole concept of SHLVs (e.g. LEO assembly, tugs). Ares V, possibly coupled with a proto-COTS instead of Ares I (I fully agree on Ares I being a poor idea), was big enough to at least do single-stack lunar landings to compensate for its presumably slow cadence. If any single thing should have been preserved from Constellation, it's the Ares V, instead of its awkward smaller cousin the SLS.

*I don't actually know what cadence was projected for Constellation. I could be wrong, but I suspect it would've wound up being similar to SLS.

I'd also argue that there's some sense in proposing the Ares I. It fulfills the purpose of separating crew from cargo, and would have been a reasonably cheap way to get the astronauts to space. Later studies by the Air Force indicated "hold on, the SRB exhaust will murderdeathkill any abort", and SRBs are in general probably less safe, but it wasn't an insane idea... just a sub-optimal choice that was fortunately cancelled before astronaut lives were risked on the thing.

Also (despite my name: I swear I had this screen-name long before FH ever flew), I'm pretty skeptical of the Starship/Superheavy. There's a chance it might work, but I'd rather not bet the farm on it anytime soon. What I would argue is that, between FH, New Glenn, and Vulcan/Vulcan Heavy, there's a pretty solid chance we'll be able to throw some heavy-duty modules into space with commercial LVs. With the immense flaws in SLS, I'd rather go for missions based on assembly of mid-sized modules on multiple commercial HLV launches than continue pouring money down the SLS drain. Developing LEO assembly and/or tugs would also fit well into the mandate of developing new technology to promote the commercial sector.

EDIT: And OmegA. Everybody always forgets about OmegA, even me.

Finally: I'm given to understand SRBs are really not the greatest choice for LVs period; LRBs are quite cost-competitive. What they do do is keep around institutional knowledge on how to build Totally Not ICBMs. For a purely cargo SHLV, on which astronaut lives didn't rest, I'd be willing to live with SRBs courtesy of that... though my inner KSP player wants to swap those out for Pyrios boosters.

Edited April 11, 2019 by Starman4308

[Bill Phil]

2 hours ago, jadebenn said:

Folks, let me elucidate you all on the sad story of a project known as DIRECT. The idea was simple, and may sound familiar: build a new heavy lifter out of old shuttle parts to minimize downtime in-between the shuttle transition. It was basically an engineer revolt from inside NASA against the (ill-fated) Ares I and V rockets of the Constellation program. DIRECT is similar to SLS, and in many ways was the program's "father," but it was distinct from the end-product in a number of ways.

The primary motivation behind DIRECT was to close the launch gap. The shuttles were going. It had already been decided and no-one wanted to revisit that. However, the promise of DIRECT was that the majority of the shuttle workforce and infrastructure could be retained. This is a big deal: any more than a few years downtime and a large amount of that knowledge just goes away as people retire or move onto new jobs. DIRECT was supposed to prevent this. Here's how:

This rocket, known as Jupiter, is basically just a shuttle rocket, minus the... y'know, shuttle. Very little modification. The biggest change would be moving the three SSMEs to the bottom of the external tank and flattening its top. The resulting rocket would be highly capable, with a payload capacity of about 70 mT to LEO per launch. Hey, wait a minute! Doesn't that number sound familiar? Don't worry, I'm getting to that.

When the Obama administration canceled Constellation, NASA and Congress freaked out. Eventually, with the help of the DIRECT people, a compromise was reached. Orion was "un-cancelled" and Congress wrote the goals of the DIRECT program (more-or-less) into law. They called the resulting rocket the Space Launch System, or SLS for short.

Feeling satisfied, DIRECT disbanded. They didn't get everything they wanted, but they felt pretty good about this new "SLS" thing. After all, it seemed to follow the principles they had set out that would allow maximum commonality with shuttle equipment and minimize the gap between the shuttle program and its successor. What could go wrong?

Well, uh, NASA management interpreted this act far differently than they intended, and the result was essentially a fusion between the original vision for DIRECT and the canceled Ares V. Unfortunately this brought about the exact situation DIRECT was meant to avoid, and well... let's just say that most ex-DIRECT people you'll find won't have very nice things to say about the SLS.

From what I recall the Augustine commission found that the Ares V wouldn't be ready until sometime in the 2020s...

I guess they were more accurate than anyone initially thought.

What people weren't expecting regarding SLS was... a lot, really. It's a mess. Just a mess. One that's gonna take half a decade or longer to really clean up. 

I'm someone who agrees with Shuttle-C. It was a good idea. The Orbiter itself was already 100 something tonnes, making the Shuttle stack a super heavy in that aspect. So just replacing the Orbiter with a cargo pod using SSMEs near end of life would've been great.

Really wonder why we didn't do that...

[tater]

2 hours ago, jadebenn said:

I agree that the SLS is a flawed program, but I think it has its uses. My view of its utility mainly comes from my intense skepticism over commercial SHLV capability. I'd be happy to be proven wrong on this point, I assure you, but I just don't see it happening anywhere near as soon as they say it will. I'd rather not derail the thread by explaining every minute detail of why I feel this way, so let me just do the abridged version: Until we have a commercial SHLV flying, I do not feel comfortable cancelling the SLS. I'm fine with giving LEO over to the likes of SpaceX, but I don't think they're ready for BEO yet.

We're in some agreement here, actually, though I would feel far more comfortable cancelling elements of the program, I see little sunk cost that we will recover.

Orion is capable, and with a decent SM, it could be useful (on top of New Glenn?).

A good cryo upper stage would be awesome, but ULA is doing that, regardless (and BO?).

Starship is the game-changer here, but it needs to demonstrate itself before it's able to be used by NASA. I'm fairly confident they'll get it working, though the reuse aspect (number of uses) is the huge, huge uncertainty here. The booster is pretty trivial, honestly, and even just a really big stick F9 (Super Heavy), with a throw away stage 2 is a game changer, honestly (assuming steel allows easy reuse of the FAR less stressed booster). Heck, a SpaceX stage 2 designed for just reuse in space (as a refillable tug) would be a profound improvement.

[RCgothic]

So both second stages are undersized. The core stage is oversized but too anaemic in terms of thrust. And the boosters don't burn long enough. 

If core and boosters were able to put a sizeable payload in orbit without a second stage the problem wouldn't be half as bad. That would make it mission agnostic, just change what you stick on top of it.

If I were designing a SHLV today it would probably look a lot like SA-513 that launched Skylab with flyback side boosters. Two and a half stages to orbit and whatever you like on top.

[jadebenn]

6 hours ago, Starman4308 said:

First: I am seriously enjoying this conversation.There is a minimum of talking past each other.

 The fundamental issue I see with SLS is that it can't practically do any of the big missions (e.g. ARM, lunar landings, Mars) without developing the technologies that obsolete the whole concept of SHLVs (e.g. LEO assembly, tugs). Ares V, possibly coupled with a proto-COTS instead of Ares I (I fully agree on Ares I being a poor idea), was big enough to at least do single-stack lunar landings to compensate for its presumably slow cadence. If any single thing should have been preserved from Constellation, it's the Ares V, instead of its awkward smaller cousin the SLS.

If we need Ares V launch capability, Block 2 can theoretically do that. Though like I said earlier, even if the other SLS variants end up living a long, happy, productive service life, I wouldn't count on Block 2 ever being built, mainly because the jump between them is so big. You know how SLS Block I turned out to be about 25 mT stronger than it was originally supposed to be (largely due to the aforementioned mods that sunk DIRECT)? Well Block 2 as currently designed has the opposite problem. Thanks to the changes made to I and IB, just slapping some better solids on the side ain't gonna cut it anymore. You'll need a new upper stage or something better than solids (like those F1Bs) to hit that 130 mT figure now, and that means you'll need to mod the VAB, MLP, and launchpad appropriately. It's a lot bigger of a jump than moving from Block I to IB, and even that was looking pretty sketchy for a while.

To be honest, the limited payload is kind of a blessing in disguise for the lunar program? Stay with me here. The SLS's margins mean the Gateway is necessary for moon landings, which means NASA has a hell of an easier time justifying why it needs funding for permanent lunar infrastructure to Congress. If we had the full capacity of the Ares V or an SLS Block 2 available right now, it'd be hard to resist the temptation to pull off another "flags and footprints" mission like Apollo, and then we could be waiting another few decades for a return depending on how commercial space shakes out. With LOP-G, while it's not as efficient from a pure financial perspective, you're "tangling-up" the politics enough that it's going to be a sustained thing. You have the commercial companies who will be launching supply missions to it, you have the international partners who want to see their money in use, you have the contractors that are building modules for it, etc. It's a lot like the ISS in that regard: even if it's just a target, its existence stimulates demand that wouldn't otherwise exist.

6 hours ago, Starman4308 said:

 *I don't actually know what cadence was projected for Constellation. I could be wrong, but I suspect it would've wound up being similar to SLS.

There are probably figures out there, but considering the state of the program when it was cancelled... I wouldn't put too much stock into them. Around SLS sounds about right. The Ares I in particular would've suffered a lot from essentially being made redundant with COTS; there's a reason that an ISS-oriented SLS was considered for, at most, half-a-year into the project's development before being unceremoniously dropped (which once again ties into the DIRECT thing, but I digress).

6 hours ago, Starman4308 said:

 I'd also argue that there's some sense in proposing the Ares I. It fulfills the purpose of separating crew from cargo, and would have been a reasonably cheap way to get the astronauts to space. Later studies by the Air Force indicated "hold on, the SRB exhaust will murderdeathkill any abort", and SRBs are in general probably less safe, but it wasn't an insane idea... just a sub-optimal choice that was fortunately cancelled before astronaut lives were risked on the thing.

Fair point, and we have the benefit of hindsight, but I can't see a future where it would've worked out. Even without NASA's assistance, the commercial space market was really beginning to heat up. For all the criticism of SLS, it at least has something that other rockets can't replicate right now. Ares I would not be so lucky, assuming it was ever built. They didn't know this at the time, of course, so I can't be too harsh on them, but in the end it was always going to be a doomed rocket.

6 hours ago, Starman4308 said:

 Also (despite my name: I swear I had this screen-name long before FH ever flew), I'm pretty skeptical of the Starship/Superheavy. There's a chance it might work, but I'd rather not bet the farm on it anytime soon. What I would argue is that, between FH, New Glenn, and Vulcan/Vulcan Heavy, there's a pretty solid chance we'll be able to throw some heavy-duty modules into space with commercial LVs. With the immense flaws in SLS, I'd rather go for missions based on assembly of mid-sized modules on multiple commercial HLV launches than continue pouring money down the SLS drain. Developing LEO assembly and/or tugs would also fit well into the mandate of developing new technology to promote the commercial sector.

I think what the HSF division of NASA is terrified of more than anything is being confined to LEO once again. They accepted it after Saturn, and they did a lot of cool stuff in there, but everything I "get" from them shows that they consider it to be used-up at this point. They've done pretty much everything they wanted to do there, and learned pretty much anything they wanted to learn. And they did learn things. NASA's a hell of a lot better at stations now than they used to be for example, and you can basically thank their cooperation with the Russians on the ISS for that. But they're tired of being limited to Earth science, and I can't really blame them. I mean, honestly, if you look at some of the last shuttle missions, we were really starting to scrape the bottom of the barrel on "scientific LEO stuff we can justify needing humans to do." 

The current plans for LOP-G suggest to me that NASA is interested in trying out the principles of refueling tech and re-usable orbital architecture. I just think they're scared of doing it in LEO because then Congress might ask the question, "Well, why are we funding this BEO platform then?"

6 hours ago, Starman4308 said:

EDIT: And OmegA. Everybody always forgets about OmegA, even me.

OmegA? Is that some kind of supplement? Well no thanks, I already had my vitamins today. 

Nah but in all seriousness, for a platform that's basically "here's our leftover spaceship parts put together," it's a pretty neat and practical idea. Just... not a very interesting one.

6 hours ago, Starman4308 said:

Finally: I'm given to understand SRBs are really not the greatest choice for LVs period; LRBs are quite cost-competitive. What they do do is keep around institutional knowledge on how to build Totally Not ICBMs. For a purely cargo SHLV, on which astronaut lives didn't rest, I'd be willing to live with SRBs courtesy of that... though my inner KSP player wants to swap those out for Pyrios boosters.

Perhaps I should've clarified. It's not so much the use of SRBs that boggles me with the Ares I, it's the exclusive use of them (or, it, rather). When you've got a beefy core stage with a poor initial TWR, SRBs make a lot of sense. Having "thrust-in-a-can" is insanely useful for launch, and on sensibly-designed platforms, they pose little additional risk over liquid rockets. Key phrase being "sensibly designed," of course.

So why NASA would ever want to make an orbital spacecraft that's entirely reliant on an SRB initial stage escapes me. That's using none of their advantages for all of their downsides! This is probably one of the times where I'd honestly accept, "because we wouldn't get funding without using SRBs," as the most logical answer.

4 hours ago, tater said:

Starship is the game-changer here, but it needs to demonstrate itself before it's able to be used by NASA. I'm fairly confident they'll get it working, though the reuse aspect (number of uses) is the huge, huge uncertainty here. The booster is pretty trivial, honestly, and even just a really big stick F9 (Super Heavy), with a throw away stage 2 is a game changer, honestly (assuming steel allows easy reuse of the FAR less stressed booster). Heck, a SpaceX stage 2 designed for just reuse in space (as a refillable tug) would be a profound improvement.

Huh... yeah, I basically agree with you here. The tech behind Starship isn't crazy or unrealistic. My hangup has always been its business plan. It reminds me a little too much of the shuttle when a platform's promising low, low, prices predicated on the assumption that it can handle a bazillion launches per year and bring costs down due to reusability. I get the two aren't really that comparable technically, but that kind of business plan makes me nervous nonetheless, because there's a lot of ways it might not work out.

25 minutes ago, RCgothic said:

So both second stages are undersized. The core stage is oversized but too anaemic in terms of thrust. And the boosters don't burn long enough. 

 If core and boosters were able to put a sizeable payload in orbit without a second stage the problem wouldn't be half as bad. That would make it mission agnostic, just change what you stick on top of it.

I don't think that's an entirely accurate assessment. You're correct when you say that (compared to optimum), the SLS core stage is over-sized and doesn't have a lot of thrust, but trust me on this: the boosters burn long enough. Think of the SLS core as a 1.5 stage rocket. It's got a huge sustainer stage coupled with two "thrust-in-a-cans" to get it off the pad, and that core stage burns for a long time, doing the work of what would be two stages in most rockets.

If you want to make the architecture better, you basically either strap something bigger with tons of thrust onto it instead of the SRBs (like that Dynetics F1B proposal), or you stick a bigger stage on the top, possibly above the already-existing one. Both of these options were at one point considered by the mainline program, and the fact that we're stuck with either an Interim Cryogenic Propulsion Stage that's no longer looking very "interim," or an Exploration Upper Stage that will either disappear or be refined into what would be more accurately labelled a "Lunar Insertion Stage," is really an accident of history.

Basically, the upper stage is really the bottleneck right now - and it's not an easy fix.

Edited April 11, 2019 by jadebenn

[tater]

3 hours ago, jadebenn said:

Huh... yeah, I basically agree with you here. The tech behind Starship isn't crazy or unrealistic. My hangup has always been its business plan. It reminds me a little too much of the shuttle when a platform's promising low, low, prices predicated on the assumption that it can handle a bazillion launches per year and bring costs down due to reusability. I get the two aren't really that comparable technically, but that kind of business plan makes me nervous nonetheless, because there's a lot of ways it might not work out.

I think the business case is that even with only X reuses, it's cheaper to operate per launch. Cadence is not really required to lower cost. As a business, if they have 6000 employees, and they can support those with the equivalent of 20-something launches, as long as they launch that many payloads, they don't have to let people go. If the revenues decrease, then they simply cut payroll until it balances out (since they won't need to make as many rockets to support that number of customers). If the program goal is to keep those people employed, then you see what we see with SLS...

That said, the short term flight rate is likely dominated by Starlink. SpaceX needs to get 2218 of the things into LEO in the next 5 years, that's their push for a bigger, cheaper vehicle (that and NG coming soon).

[sh1pman]

14 hours ago, jadebenn said:

If they ever get to Block 2, they'll have to switch from SRBs anyway if they want to meet their payload target. Would be nice to see this a variant of this proposal revived:

I wouldn't hold my breath, though. Even if the other SLS variants have a long and successful career, I have severe doubts Block 2 will ever fly.

They look like Twin-Boar boosters

[ZooNamedGames]

On 4/10/2019 at 12:51 PM, RCgothic said:

Stage and a half to not-quite-orbit is such a bizarre architecture.

To be fair I don’t want a whole disposable booster to orbit. We have a bad enough time getting rid of our upper stages much less the much bigger first stages.

[Barzon]

2 hours ago, sh1pman said:

They look like Twin-Boar boosters

Thats what the twin-boars are based off.

[StrandedonEarth]

36 minutes ago, ZooNamedGames said:

To be fair I don’t want a whole disposable booster to orbit. We have a bad enough time getting rid of our upper stages much less the much bigger first stages.

A huge empty stage in low orbit won’t last long before drag takes it down

[Ultimate Steve]

1 minute ago, StrandedonEarth said:

A huge empty stage in low orbit won’t last long before drag takes it down

It would also make a very large platform to test wet workshop on.

[ZooNamedGames]

42 minutes ago, StrandedonEarth said:

A huge empty stage in low orbit won’t last long before drag takes it down

Depends. High mass with more drag, but the drag doesn’t increase as drastically as the mass does. But I don’t have the math for drag calculations, much less microatmospheric drag, so I’ll say your right and leave it there. 

[Bill Phil]

2 hours ago, ZooNamedGames said:

Depends. High mass with more drag, but the drag doesn’t increase as drastically as the mass does. But I don’t have the math for drag calculations, much less microatmospheric drag, so I’ll say your right and leave it there. 

Well the Saturn V second stage for Skylab was in orbit for something like 2 years after launch.

[RCgothic]

There's no reason why there couldn't be a reserve for a deorbit burn once payload insertion is complete.