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[New] Space Launch System / Orion Discussion Thread


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5 minutes ago, RyanRising said:

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.

A modified, expendable Starship-Superheavy could *probably* do it without refuelling. I haven't done any calculations so please don't quote me on that :P

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On 2/23/2021 at 8:02 AM, RyanRising said:

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.

Ouch, basically.

Let's assume a lunar module. Apollo Ascent was roughly 2.4t dry for 2 people, so let's assume double that for 4, plus 100% again for an extended stay and a bit more comfort. Roughly 7t. Plus return with 1t of samples. To get back to LLO (1730m/s) takes 7 more tons of propellant at 310 ISP to give a bit of margin for rendezvous (1910m/s) so the ascent stage will weigh 14t landed, 15t on launch, and 8t back in LLO.

To land the ascent stage (14t) from LLO plus 1t of cargo might be 21t landed, assuming 6t for the stage dry (again, a little under 3x Apollo). To get there from LLO (1730m/s) including a decent landing margin (2110m/s) is 21t of propellant at 310 ISP, so 42t total for the lunar lander system.

Then we need to know how much is needed to return to earth. Orion weighs 10.4t and the ESM weighs about 4.9t dry for its original 8.6t of propellant. It'll need a bit more propellant to shift Orion and 42t of LM into LLO, so it'll need to be stretched a bit. It'll work out at about 7t dry with larger tanks (see later). Plus we've taken 1t of samples from the surface, so that's 10.4+7+1= 18.4t dry. To send that back to earth (820m/s)with some margin (880m/s) requires 6t of residual  propellant in the tanks at 319s ISP.

So! Now we know how much has to be braked into LLO by the ESM. 42t of lander (inc 1t landed cargo). 10.4t Orion. 7t ESM. And 6t propellant to get home. 65.4t "dry", although in this case dry just means mass at end of burn because there'll be residual propellant in the ESM. To drop that into LLO from TLI (820m/s) would take 24t of propellant, plus some margin for rendezvous/ orbital manoeuvres/station keeping/ (980m/s). So we need to send 65.4t payload plus 24t fuel is 89.4t to the moon from LEO not counting Earth Departure Stage.

(Note that the total fuel for the ESM is therefore 30t, or 21.4t extra. At 10% tank fraction for hypergolic tanks that's an extra 2.1t on the original 4.9 gives the new dry weight of 7t I've been using.)

To send 90t near enough to TLI from LEO (plus ~5t of payload attach fittings) takes 115t of hydrogen and 12t of earth departure stage. SLS would therefore have had to be designed to put around 220t into LEO. That's more than twice its block 1 configuration and even 90,t more than Block 2.

 

 

But is there a rocket in development that can do it?

At 370s ISP,  a Starship Derived Stage would need to put roughly 380t into LEO to send 95t of payload/PAF and 61t of stripped down Starship to TLI. 225t propellant required.  That sounds implausible, but I'll run some numbers anyway.

Starship can put ~100t of payload into LEO in its reusable configuration. That's not counting ~30t of landing fuel, or the ~80t dry mass, 210t all inc. Extraneous weight like flaps, fairing and heat shield can be deleted. Include the landing fuel for departure instead and take more fuel instead of the unnecessary bits and an expendable version could be 61t for the stage (5% of 1220t propellant -assuming Stainless isn't quite as good as F9US's 3.5% despite Starship's square/cube advantage) and 95t for payload and PAF, leaving 54t of fuel (210t total in LEO). That's still 174t short of TLI.

So we look at Superheavy. How much margin is wasted on an RTLS landing Vs expendable? It's hard to be sure. It's thought that F9 takes a roughly 40% payload penalty when going RTLS, so let's go with that. If 210t to LEO is 60% of Superheavy's expendable capability, it might be able to manage ~350t to LEO fully expendable.

So no. Not even fully expendable Starship/Superheavy could do that in a single launch.

 

However! That assumes the starship derived rocket is lugging an entire starship to TLI, which is carrying oversized tanks for 1200t of propellant because it's also doing the job of an upper stage. That isn't a disadvantage I put on the hydrogen powered equivalent, so let's look at a raptor derived 3rd stage, which would be much lighter!

With 150t of propellant, a Raptor 3rd stage could weigh 7.5t. Plus 94.5t of payload  is 250t to LEO. That should be well within the capabilities of an expendable Starship/Superheavy!

Edited by RCgothic
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1 hour ago, RCgothic said:

Ouch, basically.

Wow. Thanks for doing the math! I was expecting a ridiculous result, and boy howdy I guess I got one. I think this could be used as a good preface to introducing modern moon missions: it explains why doing things like Apollo did doesn't scale up well at all, and why we need to take a different approach this time around. Tyranny of the rocket equation indeed.

 

Edited by RyanRising
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5 minutes ago, RyanRising said:

Wow. Thanks for doing the math! I was expecting a ridiculous result, and boy howdy I guess I got one. I think this could be used as a good preface to introducing modern moon missions: it explains why doing things like Apollo did doesn't scale up well at all, and why we need to take a different approach this time around. Tyranny of the rocket equation indeed.

 

Sure, but there were other options between "do it Apollo style" and "do it SLS style", even without considering the launchers that have come along in the mean time.

Capsule and lander LLO rendezvous with a cadence of 4 missions/8 launches per year should have been possible if SLS and Orion had actually be designed coherently. If SLS and the ESM were a little bigger (B1B as a base) and/or Orion was a little lighter.

EOR was and remains viable, with/without Lunar rendezvous as well. Delta IV Heavy and Atlas V both could have been crew rated with a will. Then the Falcon family came along.

You just look at the program and go "yes, we're going back and that's cool, but we could be doing this so much better."

And despite NASAcs continuous use of the political Nov 2021 date for Artemis 1, multiple sources now hearing the realistic internal target is NET Feb 2022:

 

Sure I've seen at least one other as well, but struggling to dig it up right now.

 

 

 

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6 hours ago, RyanRising said:

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.

I think that they'd need to be throw at least 60-70 tons to TLI to be able to use the Orion capsule on a single stack lunar surface mission. That's not even on the table for SLS, ever. Not Block 2, not advanced Block 2.

^^^Note I am assuming a minimalist landing, Apollo style.

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11 minutes ago, tater said:

I think that they'd need to be throw at least 60-70 tons to TLI to be able to use the Orion capsule on a single stack lunar surface mission. That's not even on the table for SLS, ever. Not Block 2, not advanced Block 2.

^^^Note I am assuming a minimalist landing, Apollo style.

The difference between what 2 people need for a brief excursion and what 4 people need for an extended stay plus a tonne of cargo retun gets quite large, aye.

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2 minutes ago, RCgothic said:

The difference between what 2 people need for a brief excursion and what 4 people need for an extended stay plus a tonne of cargo retun gets quite large, aye.

Yeah, I think I did the math on that a long time ago in this or the Artemis thread, and assumed just ANY ability to replicate Apollo.

A "sortie lander" could be a thing if you pre-deploy a habitat, however. That is still within the spirit of a sustainable presence, and I would fully support such a system, even if ridiculously expensive. Ie: I'd not be constantly bashing SLS/Orion if if could send humans to the lunar surface in one go, since we could then use other capabilities to send a habitat, rover, etc ahead, and SLS/Orion is just the crew transport.

 

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Working an Apollo lander through my spreadsheet (~15t) comes up with about 64t to TLI with Orion, so yeah I agree with your figure.

 

That'd be 155t to LEO with SLS, which isn't on their upgrade path at all. 

Ironically, uprated Saturn V with F1As could probably have done it, but TBH safety is one of the few things you can't really fault SLS Orion on. Saturn V was probably lucky not to lose a crew, nevermind the crew they almost lost on Apollo.

Edited by RCgothic
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2 minutes ago, RCgothic said:

Working an Apollo lander through my spreadsheet (~15t) comes up with about 64t to TLI with Orion, so yeah I agree with your figure.

What's so sad/annoying/enraging is that it's not like NASA doesn't know this.

That number—the minimum TLI capability for SLS/Orion to be useful for any crew mission at all—is right there. That's the target.

Maybe not for Block 1, Block 1B, etc, but if there is no evolution to "65t to TLI" SLS is a complete waste of time and treasure.

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21 minutes ago, tater said:

What's so sad/annoying/enraging is that it's not like NASA doesn't know this.

That number—the minimum TLI capability for SLS/Orion to be useful for any crew mission at all—is right there. That's the target.

Maybe not for Block 1, Block 1B, etc, but if there is no evolution to "65t to TLI" SLS is a complete waste of time and treasure.

The 38t to TLI that B1B can do is more than enough to get Orion into LLO with a stretched service module. They should have just come straight to this as the baseline version.

Then send the lander on a second launch. 38t doesn't get you 4 people for an extended stay, but it might get you 2 for an extended stay. 38t to TLI is roughly 28t in LLO, nearly twice Apollo.

But there's no plan to upgrade the ESM, and they couldn't build SLSs fast enough to support this anyway.

"But even a long stay isn't a sustainable presence, that's why we need gateway!" they counter-argue despite gateway going to be mostly vacant and not actually anywhere interesting in itself. That's just a half-measures. Go the whole way and make a permanently inhabited surface base. Cheap frequent cargo is what enables sustainable presences. Does SLS do that? No.

Edited by RCgothic
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1 hour ago, RCgothic said:

The 38t to TLI that B1B can do is more than enough to get Orion into LLO with a stretched service module. They should have just come straight to this as the baseline version.

LLO is not a useful crew mission, IMHO, though I agree they can pump up the SM and do that (heck, they might be able to take something with them (a Soyuz-like "orbital module"?) if they could put IVF on the EUS and do even some of the LOI burn with the EUS).

Flight cadence, cost, and 2 launches don't cut it for me (2 SLS launches). I agree that sans B1B, they should not have bothered. There is no possible evolution to 65t to TLI though.

It always comes back to the very first problem with SLS/Orion: "What is the spaceflight mission goal?" (have to add the italics because we all know the real "mission")

I think any useful mission needs to be useful from the start. If the mission requires commercial launch support, then start from a clean sheet with that assumption (and then cost matters). Once commercial providers are on the table, different mission architectures start looking more valid. That's why I tend to judge SLS on it's single launch capability—and that judgement is, "SLS is completely worthless."

I think the idea of a SHLV for BLEO human spaceflight is a reasonable goal for NASA, BTW, and I am not overly concerned about the pork aspect, that's how the sausage is made. I do think it should actually have the ability to accomplish some interesting mission, however. Look at the recent Mars rover. Interesting mission, and it has successfully started. What would we think of Perseverance if it had been sent "kinda near Mars" and they would iterate it a few times also "kinda near Mars" with a goal that eventually a commercial provider sends something to bring the rover to the surface? We'd rightfully say the first X launches were a waste of time.

Any "jack of all trades" BLEO SHLV needs to at the very least be able to accomplish the minimum mission, and for a "jack of all trades" it should likely be able to do more than 1 type of mission. SLS/Orion is not a Jack of all trades, master of none—it's just the "master of none." Or Jack of no trades.

Ares V was designed for 60-70t to TLI. Orion was sent to LEO with Ares I in that architecture. Docks with Lander attached to Ares V upper stage, goes to TLI.

 

Edited by tater
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Not to get into politics or so, and obviously I'm not worrying very much on the SLS budget, but maybe things are not that bad for it?

As most of excessively SLSed money stay in same economics rather than dissolve in air, just get redistributed between some other companies, workers, and so on, maybe actual losses of SLS are not even close as great as it seems?

Say, burnt fuel is lost. An aluminium tank thrown to the Moon is lost. 
But salaries aren't lost money. Credit payments are also just redistributed inside the same economics, not just buried. And so on.
Even built engines can be melted and reused.

So, maybe actual SLS cost is much lower, and it is not that expensive?

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5 minutes ago, kerbiloid said:

Not to get into politics or so, and obviously I'm not worrying very much on the SLS budget, but maybe things are not that bad for it?

As most of excessively SLSed money stay in same economics rather than dissolve in air, just get redistributed between some other companies, workers, and so on, maybe actual losses of SLS are not even close as great as it seems?

Say, burnt fuel is lost. An aluminium tank thrown to the Moon is lost. 
But salaries aren't lost money. Credit payments are also just redistributed inside the same economics, not just buried. And so on.
Even built engines can be melted and reused.

So, maybe actual SLS cost is much lower, and it is not that expensive?

Cost is an upfront measure, how the money gets distributed after it’s spent doesn’t lower it. It’s like, if I go to Starbucks and buy a coffee, that $5 will get distributed amongst the workers, corporate, and maybe even wherever they get the materials for it. Those people will use that money again to do other stuff. But the coffee still costs me $5. 

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4 minutes ago, RyanRising said:

Cost is an upfront measure, how the money gets distributed after it’s spent doesn’t lower it. It’s like, if I go to Starbucks and buy a coffee, that $5 will get distributed amongst the workers, corporate, and maybe even wherever they get the materials for it. Those people will use that money again to do other stuff. But the coffee still costs me $5. 

But if instead of you this money gets John Doe and buys the coffee, this doesn't make your and John common boss spend more money on his personnel coffee.

So, if instead of a hundred of cars build one rocket, this just changes the money route, not their amount.
Just rocket makers will get more coffee, while car makers - less. But anyway all these money come to Starbucks.

Edited by kerbiloid
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1 minute ago, kerbiloid said:

But if instead of you this money gets John Doe and buys the coffee, this doesn't make your and John common boss spend more money on his personnel coffee.

I’m a little confused now. I’m buying John Doe? We’re spending the same amount of money on more coffee?

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1 minute ago, RyanRising said:

I’m a little confused now. I’m buying John Doe? We’re spending the same amount of money on more coffee?

You are colleagues working in departments of same company.

You build cars, he builds rockets.

Starbucks workers buy these cars and T-shirts with rockets on the money which you and John bring to them, then the company pays your and his salary from this money.

Edited by kerbiloid
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2 hours ago, RCgothic said:

The difference between what 2 people need for a brief excursion and what 4 people need for an extended stay plus a tonne of cargo retun gets quite large, aye.

I've often thought what would have happened had NASA repurposed an Apollo launch (after Apollo 11) to launch the LEM+whatever other supplies into lunar orbit while the crew would take another Apollo (with more supplies, and possibly more room for whoever was stuck on board) to the Moon.  Unfortunately, there would be a strong chance that the crew would be riding Apollo 13 with no LEM to bring them home:(.

You could fit a lot of cargo on a Lunar vessel that never intended to come home.

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Quote

You are colleagues working in departments of same company.

You build cars, he builds rockets.

Starbucks workers buy these cars and T-shirts with rockets on the money which you and John bring to them, then the company pays your and his salary from this money.

OK, but that money could have easily come from somewhere else. Our work making money is how the company funds us doing the work and drinking coffee. NASA gets money from the government instead, but it doesn’t really matter - money is interchangeable, so it shouldn’t matter where that money comes from when you spend it.  Just cause we made revenue doesn’t make our expenses less real. And just cause NASA money flows to other things, and, in part, itself (through the US government) doesn’t make SLS cost less. 

Edited by RyanRising
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46 minutes ago, RyanRising said:

OK, but that money could have easily come from somewhere else.

All possible "elses" (well, mostly) belong to same national economy.
So, all money spent from budget anyway return to the same budget, just routed alternatively.

So, is it so imortant if SLS is nominally overexpensive? Isn't it actually much cheaper in sense of money spent without return (say, excessively burnt fuel)?

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22 minutes ago, kerbiloid said:

All possible "elses" (well, mostly) belong to same national economy.
So, all money spent from budget anyway return to the same budget, just routed alternatively.

So, is it so imortant if SLS is nominally overexpensive? Isn't it actually much cheaper in sense of money spent without return (say, excessively burnt fuel)?

That fuel doesn't return to the economy, but the money spent on it does in exactly the same way the money spent on SLS does. Almost all ways you can possibly spend money have the same effect.

Edited by RyanRising
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Economically it might not make much difference whether $ are spent on coffee, SLS, or Falcon Heavies, economic stimulus being economic stimulus, but if what you're interested in is Spaceflight Milestones Achieved then there'll be a vast difference in outcomes depending on which you spend money on.

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