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I live on the Space Coast (also work in the industry, and thus, have access to well - rumors). The SLS (Senate Launch System as we call it here) was pretty cool

I live on the Space Coast (also work in the industry, and thus, have access to well - rumors). The SLS (Senate Launch System as we call it here) was pretty cool to watch in person for the uncrewed mission. Nevertheless, as Destin pointed out, it has some massive challenges and headwinds NASA and contractors are cemented in and must accept the SLS is the selected system we are going with. Rumor (please take it for what that is worth - rumors) are, many here are very suspect of even a 2025 crewed flight.

disillusioned 3y ago
At what point do we seriously consider the idea that Starship will lap SLS in capabilities and timing, and cancel SLS altogether? I feel like everyone's thinking this, but there's too much pork pressure and sunk cost fallacy to finally just ditch what's turning out to be a misguided approach, nearly 20 years in. It's a platform built of new stock but very old SSMEs, still using hydrogen and all the problems that brings with it, on a non-reusable basis, with apparently varying quality even amongst identically specced but different vendored mission critical parts. The litany of issues they're outlining here are all varying stages of terrifying, and things that shouldn't be getting caught in this validation phase of a rocket that's actually already had a successful-ish launch demonstration. Meanwhile, Starship keeps iterating like crazy, the way SpaceX does, and with significantly reduced relative complexity, on a vertically integrated platform that they have much more control over. I'm no Elon fanboy, but Starship is going to win this race, right?
- pfdietz 3y ago
  SLS can't even beat F9/FH, never mind Starship. It has already lost.
  - ginkgotree 3y ago
    The SLS delivered a crew capable Space Vehicle to Lunar orbit, and the space vehicle returned a crew capable capsule back the Earth. The lift capacity of FH is not capable of that. This is all about SWaP: Size, Weight, and Power.
    - pfdietz 3y ago
      The idea that all the components have to go up on a single launcher is nonsense used to justify SLS. It's political engineering, not rational mission design.
      - ginkgotree 3y ago
        I don't think a Falcon Heavy would retain enough fuel once getting itself in orbit with 0 payload to give enough delta-V to the entire Artemis Space vehicle. That burn has to (generally) happen in a single TLI burn. So there is actually a minimum quanta of delta-V for the mission I don't think FH could meet. You're welcome to run this in Orbital STK if you like.
        pfdietz 3y ago
        Propellant transfer. There's a reason Senator Shelby was so adamant NASA not work on it -- it greatly reduces any need for a launch vehicle as large as SLS.
        dotnet00 3y ago
        Specifically it completely eliminates the need for a non-reusable launch vehicle as large as SLS.
      - simonh 3y ago
        Granted that this is true, FH right now does not have these capabilities and SLS has already done it. For all the amazing success of FH it's completely the wrong vehicle for a mission like this, which is why Starship exists and IMHO is the future.
        pfdietz 3y ago
        The point is the mission was designed to prop up SLS, not designed to actually be worth doing. A base on the moon could be supported with FH, and much more cheaply than one supported by SLS.
- ginkgotree 3y ago
  Starship is _required_ as part of the TLI trjaectory to refuel SLS with cryos. NASA will keep flying SLS however, to demonstrate to the public and congress that it was not setting a pile of tax dollars on fire. LH2 as a fuel was a mistake, high ISP, but well, the turbopumps, plumbing, valves, etc, not to mention REFUELING LH2 ON ORBIT to replenish evap. Starship imho will lapse SLS in the next year or two. From a perspective of demonstrated spaceflight capabilities per unit cost, it will lapse it the first time Starship makes an uncrewed flight around the moon and re-enters a capsule that is recoverable with a human survivable water or land landing. Key qualifier there is per unit cost. Point is, Starship lapses SLS once it matches demonstrated spacelfight capabilities on sheer demoninator of cost.
  - two_handfuls 3y ago
    I'm pretty sure you mean "Starship will lap SLS" and not "lapse", which would inverse the meaning of what you wrote.
    - ginkgotree 3y ago
      Yep, I do
- deleted 3y ago
  [deleted]
- DylanSp 3y ago
  The problem is convincing Congress to pull the plug on SLS. Even if Starship is able to unambiguously surpass SLS technically, lobbying Congress to cancel a program that spreads manufacturing work across most of the US and that involves multiple big defense contractors [1] is going to be a tough sell. [1] Boeing for the core stage and integration, Lockheed Martin for Orion, Northrop Grumman for the SRBs, and Aerojet Rocketdyne for the SSMEs.
  - credit_guy 3y ago
    > lobbying Congress to cancel a program that spreads manufacturing It's not lobbying to cancel a program, it's lobbying to replace a program with another. That other program may bring jobs in the same places; it's actually quite convenient to do so, since there are not that many people around with expertise in rocket manufacturing.
    - DylanSp 3y ago
      Given SpaceX's heavy use of vertical integration, I highly doubt that it'll spread as many jobs around as SLS currently does.
      - credit_guy 3y ago
        It’s not going to be 100% replacement, but it could be 50%. And Musk’s lobby machine could find some more extra sweateners here and there. Or you think only Boeing and Lockheed have lobbyists?
- pclmulqdq 3y ago
  The way this often happens with government programs is that one program has to demonstrably deliver the goods before their competitors lose funding. SLS thus far has done better at this than starship. They do this with a lot of military and military-adjacent contracting - they have multiple companies develop a capability, and then theoretically get some choice about which one to buy from as well as having some strategic redundancy. In many ways, NASA and others have de-risked their heavy lift capabilities by putting together at least two sources. Artemis has sole-source contracts to both SLS and Starship for separate things, but the program is creating two separate heavy-lift vehicles. Starship has to innovate its way into orbit first (the most recent flight got the altitude for LEO, but not the velocity) and then around the moon to catch up to where the SLS program is today. As far as I can tell, many space folks outside of SpaceX actually have more concerns about whether Starship can deliver on its promises than whether SLS can.
  - ginkgotree 3y ago
    "First rule of government spending: why buy one when you can buy two for twice the price" - Fictional billionaire R.L. Hadden, in Carl Sagan's "Contact"
  - Georgelemental 3y ago
    > the most recent flight got the altitude for LEO, but not the velocity Starhship could easily have reached true orbit, they deliberately stopped just before it for safety reasons (don't want massive chunk of space junk if something goes wrong during deorbit)
    - pclmulqdq 3y ago
      Is that their line? Musk companies have used that excuse a lot when they actually can't do something (see Tesla FSD). During the test flight, they called that orbital insertion was complete after they ran out of fuel (long before reaching orbital velocity), so I'm not buying it. Also, at that altitude, there's enough drag that you can de-orbit a big metal can pretty easily by simply pointing it in a high-drag orientation. Most LEO satellites do this when their missions are over, and it takes a couple weeks.

disillusioned 3y ago

At what point do we seriously consider the idea that Starship will lap SLS in capabilities and timing, and cancel SLS altogether? I feel like everyone's thinking this, but there's too much pork pressure and sunk cost fallacy to finally just ditch what's turning out to be a misguided approach, nearly 20 years in. It's a platform built of new stock but very old SSMEs, still using hydrogen and all the problems that brings with it, on a non-reusable basis, with apparently varying quality even amongst identically specced but different vendored mission critical parts. The litany of issues they're outlining here are all varying stages of terrifying, and things that shouldn't be getting caught in this validation phase of a rocket that's actually already had a successful-ish launch demonstration. Meanwhile, Starship keeps iterating like crazy, the way SpaceX does, and with significantly reduced relative complexity, on a vertically integrated platform that they have much more control over. I'm no Elon fanboy, but Starship is going to win this race, right?

pfdietz 3y ago
SLS can't even beat F9/FH, never mind Starship. It has already lost.
- ginkgotree 3y ago
  The SLS delivered a crew capable Space Vehicle to Lunar orbit, and the space vehicle returned a crew capable capsule back the Earth. The lift capacity of FH is not capable of that. This is all about SWaP: Size, Weight, and Power.
  - pfdietz 3y ago
    The idea that all the components have to go up on a single launcher is nonsense used to justify SLS. It's political engineering, not rational mission design.
    - ginkgotree 3y ago
      I don't think a Falcon Heavy would retain enough fuel once getting itself in orbit with 0 payload to give enough delta-V to the entire Artemis Space vehicle. That burn has to (generally) happen in a single TLI burn. So there is actually a minimum quanta of delta-V for the mission I don't think FH could meet. You're welcome to run this in Orbital STK if you like.
      - pfdietz 3y ago
        Propellant transfer. There's a reason Senator Shelby was so adamant NASA not work on it -- it greatly reduces any need for a launch vehicle as large as SLS.
        dotnet00 3y ago
        Specifically it completely eliminates the need for a non-reusable launch vehicle as large as SLS.
    - simonh 3y ago
      Granted that this is true, FH right now does not have these capabilities and SLS has already done it. For all the amazing success of FH it's completely the wrong vehicle for a mission like this, which is why Starship exists and IMHO is the future.
      - pfdietz 3y ago
        The point is the mission was designed to prop up SLS, not designed to actually be worth doing. A base on the moon could be supported with FH, and much more cheaply than one supported by SLS.
ginkgotree 3y ago
Starship is _required_ as part of the TLI trjaectory to refuel SLS with cryos. NASA will keep flying SLS however, to demonstrate to the public and congress that it was not setting a pile of tax dollars on fire. LH2 as a fuel was a mistake, high ISP, but well, the turbopumps, plumbing, valves, etc, not to mention REFUELING LH2 ON ORBIT to replenish evap. Starship imho will lapse SLS in the next year or two. From a perspective of demonstrated spaceflight capabilities per unit cost, it will lapse it the first time Starship makes an uncrewed flight around the moon and re-enters a capsule that is recoverable with a human survivable water or land landing. Key qualifier there is per unit cost. Point is, Starship lapses SLS once it matches demonstrated spacelfight capabilities on sheer demoninator of cost.
- two_handfuls 3y ago
  I'm pretty sure you mean "Starship will lap SLS" and not "lapse", which would inverse the meaning of what you wrote.
  - ginkgotree 3y ago
    Yep, I do
deleted 3y ago
[deleted]
DylanSp 3y ago
The problem is convincing Congress to pull the plug on SLS. Even if Starship is able to unambiguously surpass SLS technically, lobbying Congress to cancel a program that spreads manufacturing work across most of the US and that involves multiple big defense contractors [1] is going to be a tough sell. [1] Boeing for the core stage and integration, Lockheed Martin for Orion, Northrop Grumman for the SRBs, and Aerojet Rocketdyne for the SSMEs.
- credit_guy 3y ago
  > lobbying Congress to cancel a program that spreads manufacturing It's not lobbying to cancel a program, it's lobbying to replace a program with another. That other program may bring jobs in the same places; it's actually quite convenient to do so, since there are not that many people around with expertise in rocket manufacturing.
  - DylanSp 3y ago
    Given SpaceX's heavy use of vertical integration, I highly doubt that it'll spread as many jobs around as SLS currently does.
    - credit_guy 3y ago
      It’s not going to be 100% replacement, but it could be 50%. And Musk’s lobby machine could find some more extra sweateners here and there. Or you think only Boeing and Lockheed have lobbyists?
pclmulqdq 3y ago
The way this often happens with government programs is that one program has to demonstrably deliver the goods before their competitors lose funding. SLS thus far has done better at this than starship. They do this with a lot of military and military-adjacent contracting - they have multiple companies develop a capability, and then theoretically get some choice about which one to buy from as well as having some strategic redundancy. In many ways, NASA and others have de-risked their heavy lift capabilities by putting together at least two sources. Artemis has sole-source contracts to both SLS and Starship for separate things, but the program is creating two separate heavy-lift vehicles. Starship has to innovate its way into orbit first (the most recent flight got the altitude for LEO, but not the velocity) and then around the moon to catch up to where the SLS program is today. As far as I can tell, many space folks outside of SpaceX actually have more concerns about whether Starship can deliver on its promises than whether SLS can.
- ginkgotree 3y ago
  "First rule of government spending: why buy one when you can buy two for twice the price" - Fictional billionaire R.L. Hadden, in Carl Sagan's "Contact"
- Georgelemental 3y ago
  > the most recent flight got the altitude for LEO, but not the velocity Starhship could easily have reached true orbit, they deliberately stopped just before it for safety reasons (don't want massive chunk of space junk if something goes wrong during deorbit)
  - pclmulqdq 3y ago
    Is that their line? Musk companies have used that excuse a lot when they actually can't do something (see Tesla FSD). During the test flight, they called that orbital insertion was complete after they ran out of fuel (long before reaching orbital velocity), so I'm not buying it. Also, at that altitude, there's enough drag that you can de-orbit a big metal can pretty easily by simply pointing it in a high-drag orientation. Most LEO satellites do this when their missions are over, and it takes a couple weeks.