Which Will Be First to Space – the SpaceX Starship or the SLS?

SpaceX is talking with three companies about the first commercial launch of the fully reusable Super Heavy Starship with a 2021 target date.

United Launch Alliance and NASA have been working on the Space Launch System since 2011. There was also the Constellation rocket program from 2005 to 2011. SLS and Constellation were trying to re-use Space Shuttle booster technology. However, despite spending over $20 billion (not including another $10 billion for the Orion capsule) there has not been a successful test or a live mission with SLS. NASA is still talking about a first mission with SLS in 2020 but the government Accountability Office has report which indicates that we would be lucky if SLS can launch in 2021.

The first flight test of the SLS will feature a configuration for a 70-metric-ton (77-ton) lift capacity and carry an uncrewed Orion spacecraft beyond low-Earth orbit to test the performance of the integrated system.

The SpaceX Falcon Heavy can carry 63.8 metric tons (70-tons) to low earth orbit. The Falcon Heavy has flow three times and has 90% of the lift capacity of the version of the SLS.

The development of the BFR (previous name for the Super Heavy Starship) started in 2012, when SpaceX started Raptor upper-stage engine development. By September 2017, Raptor engines had been tested for a combined total of 1200 seconds of test firing time over 42 main engine tests. The longest test was 100 seconds, which is limited by the size of the propellant tanks at the SpaceX ground test facility. The test engine operates at 20 MPa (200 bar; 2,900 psi) pressure. The flight engine is aimed for 25 MPa (250 bar; 3,600 psi), and SpaceX expects to achieve 30 MPa (300 bar; 4,400 psi) in later iterations.

In December 2018, nine months after starting construction of some parts of the first test article carbon composite Starship low-altitude test vehicle, SpaceX CEO Musk announced a “counterintuitive new design approach” would be taken by the company. SpaceX switched to a stainless steel alloy which is very heat resistant.

A Starhopper has been built from a 300-series stainless steel. The high melting point of 300-series still would mean the leeward side of Starship would need no insulation during reentry, while the much hotter windward side would be cooled by allowing fuel or water to bleed through micropores in a double-wall stainless steel skin, removing heat by evaporation.

There are now two orbital versions of the Starship being built. One is in Texas and another in Florida.

As of May 2019, SpaceX says construction of the first SuperHeavy would not start before August.

24 thoughts on “Which Will Be First to Space – the SpaceX Starship or the SLS?”

  1. More than economic incentives are required. Somebody actually has to build public infrastructure.

    Could you do that outside of NASA? Sure. But why? NASA is essentially set up to provide exactly the right kinds of things. You need to think about Chesterton’s Fence.

    Don’t get me wrong: SLS is an abomination, Orion is somewhat less abominable but still pretty bad, and there are any number of JWST-like horror stories floating around. But that’s an argument for reform, not abolition. Bureaucracies actually do important stuff, and tearing them down just because they’ve drifted off course is silly. Fix NASA instead.

  2. If there is no crew on board, maybe Starship could just roll to take care of heat instead of this porous-steel scheme. Continuously move the heated face around to the back to radiate heat away. The hotter something is, the faster it radiates energy. They’d just need the radiation rate to exceed the heating rate to make this work – and the plasma sheath and reflective surface supposedly will slow heating, but shouldn’t slow radiating.

    If the crew had seats that could rotate 360 degrees, it might work for crewed flights as well.

    Or maybe there could be a separate ‘heat shell’ that spins around the ship to accomplish the same thing – though mechanical reliability might be a concern.

  3. NASA is absolutely essential if you believe that human spaceflight beyond earth orbit is important. You can’t run a business if your only customers are eccentric billionaires. Cis-lunar and lunar surface businesses need infrastructure and high launch rates to get the capital costs low enough to attract private investment. NASA will be making that infrastructure, because NASA is the only organization that can spend the money that’s needed without making a profit on it.

    On the other hand, there is absolutely no reason for NASA to be in the launcher business, ever again. Their charter should be modified so that they’re precluded from doing so.

  4. It’s actually completely disposable. They’re not planning on recovering the SRBs.

    Orion is theoretically reusable, but they’re not planning for reuse in the first few missions, and it’s not part of SLS.

  5. In a “duh” moment, I realized that the 70 t to LEO is actually what the SLS core + SRBs can do. Put any second stage you want on the core and you’ll get more than that.

  6. pinnacle of complexity, which lead to its downfall, too much could go wrong when they tried to speed up the number of flights.

  7. Based on past performance, and economic incentive, BFR will win hands down! When ULA fails to deliver, they get a contract extension, and more money, if SX fails to deliver, they take a loss, and might even go out of business.
    I really think that NASA should be disbanded. If not, it should consist of a few managers, and a ton of accountants, and engineers to audit performance. All work should be done under performance based contracts, open to public bidding. Money for science mission hardware should come for the NSF, under contract, and bid on my private enterprise, non profits, and universities.
    The SLS is the proof that I am right. Imagine if the money squandered on SLS had been spent on contracts won by SpaceX. We would have a base on Luna!

  8. At the DearMoon preso, they said 100 t to LEO with the sea-level engines (Isp=356) only.

    If I assume 725 m/s to de-orbit and land Starship (and they might need less than this), I get pretty close to 100 t. (Kinda depends on the Starship dry mass–I assume about 94 t.) For a reusable SuperHeavy but expendable Starship (which might be an interesting cargo system while they work out the kinks with reentry), I get about 126 t.

    If I assume that vacuum engines get Isp=380, then a reusable Starship goes up to 131 t. Expendable Starship with vacuum engines would be 156 t.

    The expendable numbers would be even higher with the dry mass reduced. If you could strip out the heat shielding and fins so that dry mass was only 80 t, you’d get 170 t to LEO.

  9. That’s not really the issue, though. It’s how quickly it dies. Quick death = a real lunar program. If it lingers for 4-5 launches, though, then there’s barely enough money for a flags-and-footprints mission by 2028, and nothing to sustain it after that.

  10. “The payload capacity to Earth orbit is cited as being at least 100,000 kg (220,000 lb), making BFR” -Wiki
    What is that now projected?

  11. The Starship prototypes will make it to space faster than SLS but the first production Starship will probably fly after the SLS.

  12. Seems like it’s about 50/50 for which one gets to orbit first. I’d say the odds of Starship getting to space first are about 90%.

    That said, SLS can lift quite a bit more than 70 tonnes to LEO. It should get at least 90 tonnes to LEO.

    I’m not quite sure of the origin of the 70 tonne number. Note that SLS has exactly zero mission profiles that leave it in LEO for more than an orbit, and the TLI mission profile is designed so that the SRBs and core alone get it to a 100 x 1800 km eccentric orbit. This has the nice property that the core stage will burn up in short order, with no need to restart the engines to de-orbit it.

    My best guess for where the 70 tonne number comes from:

    SLS launch vehicle adapter (interstage for ICPS) mass: about 4.0 t.
    ICPS mass: 31.2 t
    Orion Stage Adapter: 0.5 t
    Orion ESM and CM: 26.1 t
    Orion Launch Abort System and Ogive Fairing: 7.6 t
    Total: 69.4 tonnes

    Add in 600 kg of crew and supplies and you’re at 70 t.

    But that’s using about 98% of the ICPS propellant to put Orion into TLI. If you consider the ICPS to be an actual second stage to put something into LEO, instead of TLI, the payload it can put into a standard 200 x 200 x 28.5 orbit is a lot more.

    So even Block 1 is a substantially heavier launcher than an FHE, and almost as heavy as the early versions of SH/SS. But it also costs at least $2.5B a launch and has a cadence of no greater than 1.3 per year.


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