NASA Wants You To Think SLS Can Do More Than A Saturn V
Let's see: a single Saturn V could place a command module & a lunar lander in low lunar orbit, put 2 people on the lunar surface, and then bring them home with lots of Moon rocks. And it did all of this half a century ago.
A single @NASA_SLS cannot do this. #Apollo50 #Artemis https://t.co/QUpR3mm9NS
— NASA Watch (@NASAWatch) July 19, 2019
Yes, it really will be embarrassing to NASA when the Starship/Super Heavy starts flying from Pad39a.
Or the Bezos Beast. SLS is simply too little, too late and too expensive.
And Bezos’s Beast. I hope we see them both flying for NASA.
They are commercial rockets and will fly for whoever pays for a launch and passes ITAR approval.
Actually, I hope not. Customers can sometimes make unreasonable requests. If I wanted to charter a Lear Jet, there are plenty of companies who would be more than happy to provide the service. If I said I wanted my own team of mechanics to inspect the plane before takeoff, some of them might be willing and charge me an arm and a leg, but others would just say no. If the customer’s custom requests really mess with smooth operations, then it might not be worth the money. I’d guess NASA might insist on a whole bunch of custom requirements that would affect smooth operations.
It will be interesting to see how NASA responds. Elon Musk did tweet that he thinks it would easier to convince NASA that the Starship could land on the Moon by actually doing it then by doing the paperwork for it. ?
We’ll see. But I’ve heard of a couple cases where that didn’t work. Someone at Goddard once vetoed the use of a certain part because it hasn’t been properly certified. Despite the fact that it had been used without problems many times on non-NASA spacecraft. And a company was once told by ESA that their product wasn’t good for flight because their test and development process (flying it on small spacecraft) was so different that ESA didn’t know how to evaluate it. Maybe they just got lucky with the flight use. Saying, “You mean we got lucky twelve times in a row?” didn’t convince them.
When the marketing weasels start making comparisons, you have to watch for what they leave out.
The 26 tons “SLS cargo to the Moon” listed is actually what SLS Block 1 will send to trans-lunar injection, TLI, an orbit reaching the Moon, but with no provision for slowing down or landing at the other end.
The comparison to Shuttle’s LEO payload is simply irrelevant.
Meanwhile, the Saturn 5’s TLI capacity, which they for *some* reason don’t list for us to compare? 47 tons. (48.6 tons in later production versions.)
If they ever get the EUS upper stage built for SLS Block 1b? (not likely at this point.) 37 to 40 tons to TLI.
Progress! Not…
(Forgive my irritated tone. But that poster is flat out deliberately deceptive. I do not appreciate being lied to by glaringly obvious omission. It’s insulting.)
Buzz Aldrin also pointed out the weakness of the SLS compared to a Saturn V in a talk today in the lion’s den – Huntsville. When I go online in the morning I will post a link to it. It might even be on YouTube then.
Here is the link to the article on Buzz Aldrin talking about the SLS.
https://www.al.com/news/201…
Apollo 11 astronaut Buzz Aldrin calls America’s space plan ‘not very good’
Posted Jul 18, 6:24
“This will not be the only place that I will mention something that will not sit well with a lot of people here,” Aldrin said. “It is very disappointing to me and many others to realize that the top heavy-lift rocket that the U.S. has today – the Space Launch System – and the top spacecraft the U.S. has today – the Orion – cannot get into lunar orbit with any appreciable maneuvering capability.”
“I say that to this audience,” Aldrin said, “because that is not very good for 50 years of development.”
To be fair. The Orion as originally design was suppose to have just enough Delta-V to return to Earth from the Moon. Getting it to a low Lunar orbit was the job of the Altair lander, which is the equivalent of the unfunded EUS upper stage.
However in order to get the Orion & Altair vehicle stack to TLI you need a launcher more powerful than the SLS Block 2 like the Ares V or assembled a large vehicle stack in LEO.
The fact is that mass to TLI is the best comparison you can make between SLS and Saturn V. That is/was the primary purpose of those launch vehicles.
The point is, Saturn V was optimized for this purpose (mass to TLI). SLS was crippled from the beginning due to its compromised starting point (must use Orbital ATK’s SRBs, must use SSMEs, and etc).
No disagreement from me about keeping the SRB & SSME make the SLS an inferior launcher to the Saturn V.
Using the Altair lander descent stage to brake the stack into low Lunar orbit was a kluge, and indicative that NASA had let Orion and Altair masses get out of hand relative to Ares 5 capacity. But, that’s a different part of the overall sad story…
I think they are talking Block 1 , Block 2 is higher payload ! Falcon Heavy is higher at present in terms of lifting capacity!
No, even if they do ever develop both the EUS and the “Evolved” strapons, NASA lists the block 2 at 45 tons to TLI. Still a few tons short of a Saturn 5.
https://www.nasa.gov/sites/…
Also, to be fair, F9H payload to TLI is impressive, but still somewhat less than SLS. F9H estimates I’ve seen are in the neighborhood of 12-14 tons (fully recovered) to 20+ tons fully expended payload to TLI.
Now, on cost per ton of TLI payload, F9H fully recovered (at an old SpaceX price point of $90m) comes in at around $7 million/ton.
SLS, at the claimed cost of $1.5 billion a flight, comes in at $58 million/ton. Ouch. At the actual likely SLS per flight cost of about $3 billion/year program cost (exclusive of Orion) divided by 1 flight/year, that’s around $116 million per ton to TLI, or around 17x F9H cost. OUCH.
Put another way, for $3 billion a year, with SLS you can send one (1) 26-ton payload to some near-Luna logistics rendezvous point.
With F9H, for $3 billion a year, even assuming actual cost per fully-reusable F9H TLI mission goes up to $125m, and actual delivered payload down to 10 tons, you can deliver 24 ten-ton payloads per year to some near-Luna logistics rendezvous point.
With an appropriate mix of partially fueled landers, fuel tankers, transfer tugs, and crew vehicles, how many well-equipped landings per year is that? And how soon could we ramp it up to a permanent base?
I am continually boggled at the magnitude of the opportunity we’re missing.
Here is a stat:
SLS block 1 initial mass fraction to LEO – 2.5%
Saturn V initial mass fraction to LEO – 4.1%
This despite the SLS weights 700,000lbs less and develops 900,000 more thrust at launch!
Once the SRBs are jettisoned there is a serious drop off in thrust. Then the entire core stage still remains until orbit.
I find Henry Vanderbilt’s metric of tons to trans-lunar injection (TLI) to be the better metric to compare the two. Why should anyone care about the mass fraction to LEO when the destination is the moon?
The 70 ton to LEO is the requirement set for the SLS (with a 130 ton to LEO for Block 2). That’s why I used it.
But TLI would be the following:
SLS block 1 initial mass fraction to TLI – 0.93%
Saturn V initial mass fraction to TLI – 1.3%
True, but mass fraction to LEO is also an indicative comparison. Oranges to oranges when the main mission is apples, true, but still a like-to-like comparison. And SLS still comes out markedly inferior to what the original NASA did fifty years ago.
In essence, a two-stage launcher wants a first stage that uses dense propellants that allow relatively light tank structure and powerful high thrust-to-weight engines. Less than maximum Isp (exhaust velocity) is acceptable, Isp is NOT what you want to primarily optimize a first stage for. Brute strength to lift as much 2nd stage+payload to a significant fraction of orbit is the goal.
The second stage needs maximum Isp, but needs relatively high thrust also, as it will still be working deep in Earth’s gravity well.
This describes Saturn 5 to a T. Not a coincidence. The basic reach-low-orbit part was a LOX-kerosene first stage with 5x 1.5 million lb thrust F-1 engines, and a LOX/LH2 second stage with 5x 230,000 lb thrust J-2 engines. (Then, once sorted out in LEO, the 1x J-2 third stage propels the Lunar stack to TLI.)
Von Braun & Co did NOT allow politics to cripple the essence of their design.
SLS, well, got a lot of these elements bass-ackward, for reasons of past and present funding politics – a long and sad story well enough known I won’t go into it here. Though I will mention the complete BOTCH of the J-2X development, where they spent years and billions “improving” the Saturn 5’s J-2 upper-stage engine to the point where they apparently decided they couldn’t use it…
IIRC the J-2X is really for solving the lack of performance of the Ares-1 core. Traded ISP for more thrust for sending stuff to LEO.
Ahh… Who cares? SLS is not going to be used for a single-launch lunar mission, the way the Saturn V launched Apollo. Whether it’s separate launched for an initial Gateway, lander and Orion, or something different, it’s going to be multiple launches. And once that’s a given, I have to wonder if three launches (SLS minimum, I think) or five (Falcon Heavy as an alternative) is a big difference. Or wonder what the point of comparing SLS and Saturn V is, regardless of the metric you pick.
It’s entirely political, to keep the money flowing down the SLS black hole.
As soon as you concede that any real deep-space program will need multiple launches, you run into this about SLS: It will fly once a year max. Neither the production nor the launch infrastructure will support more.
Cost aside, its flight rate limits make it a Potemkin rocket – something done to mimic the appearance of a serious space program.
Sure. And once you realize that, what’s the point of comparing the technical details of SLS’ capabilities with those of other launch vehicles? That’s just marketing and perhaps some macho bragging about who’s rocket is bigger. I’m really not in the mood for the later, especially since I’m in the middle of a “discussion” on Wikipedia over the use of “maiden” flight and whether that term is inappropriate due to gender bias. The last thing I want to hear is people saying how great they are because their rocket is big.
Which reminds of the time long ago when an interview with a local reporter was unmistakably starting to go south (is that also an unacceptable metaphor these days?) and I skipped directly to the obvious endpoint of the line of questioning: “Why, yes, us space nerds really do have a thing about massive flying flaming phallic symbols. Aren’t they wonderful?” with a big goofy smile.
Not good PR discipline, but completely worth it…
Seriously though: If they’re spending $3 billion a year on the thing, any and all mendacious marketing points need countering. It’s not like money for space exploration is so plentiful we can afford to waste that much indefinitely.