SLS as Starship backup methalox tanker / lifter

[libra]

As said in the tin. We are currently seeing how SLS lobby in Congress can be pernicious if not utterly perverse. They want their beloved Shuttle workforce workers voters to stay in business: all 28 000 people of them. All right, the SLS seems to have been granted eternal life back in 2010 NASA funding act.

So, now that SLS is ready to fly, and since it has been granted eternal life whatever its cost and flaws - let's use it intelligently at least.

In despair, I suggest to use it as a Starship backup methalox lifter.

I know, I know. It ain't reusable. It cost $2.5 billion per launch, if not more. Don't start me on this.

But - see the above points. Ok ? It exists, it is paid, Congress will ram it whatever happens, it can't be canned.

Now, what would be the pros ?

- 1 Every Starship seemingly needs 4 to 14 tanking flights to get itself to Earth escape velocity.

Just think about that number. So you want to fly that SLS, and keep your workforce buzy and employed ? Blam, there are flights. Lots of them. Plenty of them.

Let's suppose 14 flights per Starship bound to Mars. We split that 7 - 7 between the two big rockets. Boom, SLS just has gained 7 flights in its manifest. Nearly twice as much as Artemis present plans over the next decade. And that's only ONE Starship bound for Mars in, say, 2024. Now start throwing more Starships to the Moon... see the point ?

2 - Starship and SpaceX gains a backup tanker, and quite a powerful one: 70 mt to 130 mt of methalox per flight to LEO, is nothing to spit on. Don't you think ?

3 - Just like the present (and very tortured and contrieved Artemis architecture) NASA big rocket is part of a Moon & Mars grandiose mission. Congress' happy, contractors' happy, workforce' happy. SLS & Starships big rockets, NASA and SpaceX, works side by side like twin brothers.

4 - Build a dumb methalox fuel pod to go on top of SLS, with a crude GNC system to guide and dock itself toward the waiting LEO Starship. Boom, no upper stage issues anymore (EUS, ICPS, whatever).

5 - You can even start buying SLS tanker flight commercially, if you want. Boeing is happy ! So is ATK.

What's not to like ? 

[Elvis in Space]

You're joking. Right?

The cost is ridiculous and makes Starship uneconomical. NASA has no missions that require SLS to do this. Congress doesn't care if SLS only makes one flight a year or every two years. The same number of people  have to be kept on the payroll. Production rate on SLS is 2 a year at best and it takes a very long lead time for that. Far more than is required for any potential refilling mission. And you still have to figure the cost of a tanker upper stage and the likely decade long development on that. It would be like filling your swimming pool with a single use Ferrari towing a trailer. There's just nothing about cost, schedule, or need that adds up.

EDIT - And think about the flight rate. How would you launch 7 SLS boosters in rapid succession without additional pads and ground facilities? This idea requires spending a fortune to pursue an unnecessary use for an unneeded vehicle.

[Jim]

better off using FH, New Glenn or Vulcan

[DanClemmensen]

better off using FH, New Glenn or Vulcan

Or the obvious. Assuming Starship works at all, NASA has already contracted for the development and deployment of both a methalox tanker and a methalox depot as part of the Starship HLS contract. The depot will be sitting there in orbit and will already be in use as part of Artemis long before any NASA-funded alternative could be put in place, based solely on the time it would take to get all the funding and contracting done.

[Orbiter]

SLS does not have the payload capacity to launch enough LCH4/LOX to refill Starship. You'd need multiple, $4 billion SLS launches in a short time frame to avoid boiloff.

[libra]

You're joking. Right?

Partially, yes. "Ad absurdum, per aspera" if you prefers. It was kind of provocative reaction to the new episode in the HLS saga, see the thread. It incensed me. Was trying to "help" finding SLS a decent role in the Starship architecture. 

I reasoned the one and only mission that makes some limited sense for The Big NASA Rocket, is fuel lifter for Starship in LEO.

I picked "7 flights" as half of Starship 14 refueling flights - an out of the blue number.

And I'd like to ask. How many SLS could be churned per year, and launched, with the present infrastructure ? How many launches per year out of LC-39 ? Just need to know.

[DanClemmensen]

  If you are looking for missions to sustain SLS/Orion, I propose a yearly uncrewed mission to launch an Orion Capsule into an extra-solar trajectory containing a USB flash drive with a file that has the names of all the humans on Earth, or at least the names of all US taxpayers. This will continue the tradition of the names to be sent around the Moon on Artemis I.

(A USB flash drive will last 50 years or more but the data will be lost after about 2 years of non-use, so a massive development effort will be needed to create better storage solution.)

[libra]

https://spacenews.com/nasa-and-boeing-look-ahead-to-long-term-sls-production/

I have to say, two SLS core per year ain't much. For the sake of comparison, in 1996 the Shuttle achieved 8 flights in a year.

[Robotbeat]

There’s not enough money to do this in the NASA budget. There’s barely enough to do what they’re doing now.

Falcon 9 or Falcon Heavy as tankers make a lot more sense. I say Falcon 9 because FH seems relatively specialized. There are years when it doesn’t even fly, whereas Falcon 9 is launching every week. They’ve got F9 streamlined and FH isn’t. It could change. They supposedly want to do 5 FH launches this year, which implies some level of streamlining. And F9 gets a pretty substantial 16 tonnes to orbit reusably. Implies 40 F9 launches per mission, which no longer sounds insane since F9 is flying at a rate of roughly 50 times per year already. I’d be more confident in 40 additional F9 launches per year than 14 FH launches per year at this point, but probably would make sense to switch to FH for this application as you’re expending a third as many upper stages.

It’s a bit silly to have a backup launch vehicle to refuel Starship. If Starship is grounded for safety, gotta bet the lander version would be grounded (er, docked) as well. A backup launch site I can see.

If NASA wants to manage a depot and have both multiple tanker providers and multiple lander/users, then maybe. But not SLS. There just isn’t the raw capacity to use something that is 10 times the cost.

If we’re talking about a much smaller methalox lander, then perhaps an SLS would be enough. But not Starship.

New Glenn would also make a lot more sense than SLS.


Assuming 150*4=600t IMLEO is needed (this would be including the tanker dry masses and the methalox itself):
FHe is 63.8t, 10 launches
FHr is at least 45t (for same assumptions as FHe and the ratio of F9e and F9R), 14 launches
F9e 22.8t, 27 launches
F9R 16.25t (this is the only flight proven number on this list), 37 launches
New Glenn R is optimistically 45t (more realistically like 40t), 14 launches
Vulcan VC6 is 27.9t, 22 launches.

Starship R is 150t, 4 launches
Starship partially reusable (upper stage expended) 200t (I made this up), 3 launches
starship fully expendable 250t, 3 launches.

It’s notable that the LC-39a pad for Falcon 9/H is being plumbed for methalox for the Intuitive Machines Nova-C robotic lunar lander within a year.

[Elvis in Space]

You're joking. Right?

...I'd like to ask. How many SLS could be churned per year, and launched, with the present infrastructure ? How many launches per year out of LC-39 ? Just need to know.

Read my post beyond the first line. You might get two per year when everything works right.

[Vahe231991]

Although the SLS had its first launch last November and NASA is looking forward to the Artemis 2 mission, there is no way the SLS could serve as a backup methalox tanker/lifter for the Starship. As noted in a 2022 issue of Scientific American:

Even the SLS has its limitations, though. Assuming a launch in 2031, the giant rocket would still take nearly three decades to propel a proposed orbiter, called Persephone, to Pluto. And despite its immense size, the SLS is still limited by its inability for on-orbit refueling to boost its carrying capacity once in space. In their more audacious dreams of cosmic exploration, scientists have eyes for only one rocket: Starship. “Starship is not just an incremental change,” says Jennifer Heldmann of the NASA Ames Research Center. “This is a significant paradigm shift.”

[Jim]

Although the SLS had its first launch last November and NASA is looking forward to the Artemis 2 mission, there is no way the SLS could serve as a backup methalox tanker/lifter for the Starship.

Wrong.  It could serve as a one use only tanker.

[DistantTemple]

Although the SLS had its first launch last November and NASA is looking forward to the Artemis 2 mission, there is no way the SLS could serve as a backup methalox tanker/lifter for the Starship.

Wrong.  It could serve as a one use only tanker.

Yes clearly it could. But most flight plans require more than one tanker launch. In that situation it could not fulfill the tanker need on its own. Afterall SS would require insulation and active cooling to wait in LEO for a good part of a year between SLS loads. /S Also adding (decision/design/implement/qualify/etc) pipes/valves/interfaces etc for docking to an SS for fuel transfer may not be a particularly quick undertaking.