The Beast Emerges - SLS is on the pad

"Frankly, it is hard to know how to feel about this rocket. Certainly, one cannot help but be awed by a rocket that is as tall as a US football field is long. Designing, building, and testing such a large and complex machine represents a significant engineering achievement. But it’s impossible to have a rational discussion about the Space Launch System rocket and its payload, the Orion spacecraft, without considering its enormous expense, ongoing delays, and looming obsolescence.

One thing seems clear: although this fully stacked SLS rocket and Orion crew capsule have set the stage for the uncrewed Artemis I test launch later this year, the rollout does not mark the end of the beginning for this launch system. Rather, it’s the beginning of the end. This is probably the last gasp of the Apollo era of NASA that has gripped the space agency for six decades."

My first thought was that those looked like space-shuttle-type SRBs. But looking closer, they look smaller. Did anybody seriously look at using shuttle SRBs, since they already had them?

They are, with an extra section on top. The first ones will literally be Shuttle-era SRBs recycled from the Shuttle program.

Future SRBs, will be enhanced versions produced by Northrop Grumman.

The original Shuttle SRBs had 4 sections, SLS versions have 5, and thus more fuel to play with.

Using SRBs is actually a terrible idea. For human spaceflight, SRBs were never a good option as you can’t throttle them, they rattle you in a way that’s hard to compensate for, and they are not “reusable” in a way that’s cost effective. With SLS, btw, they are not reusable. They’ll just be thrown away.

Also, the ones they have for Artemis I are so old now, that the fuel mix is past its expiration date and may be crumbling on the inside.

If those are actual shuttle SRBs, then that rocket is a lot bigger than I thought.

I understand that they actually wanted LRBs for the shuttle, but initial cost killed it.

I can’t speak to the other objections, but I’m unclear as to why not being able to throttle the SRBs is an issue, when any needed throttle adjustments can be made (or should be able to be made) with the liquid-fueled central stage (although I understand that early versions of one of Space-X’s liquid-fuel engines couldn’t be throttled).

Reduce shaking, tailor thrust out to conditions in the atmosphere so maybe save thrust lower down and keep more thrust going right before staging and save your upper stage propellant.

Also; is this design something you could move towards reusability? You need engines that can throttle to re-land that core stage. Having SRBs you can’t throttle nor reuse is just a waste.

I find it Ironic the market values things in this way. I have to ask you @alaska_slim is this the market saying one is of more value than the other.

I know aerospace industry as a whole is worth 447 billion. It’s just that our government created it but never really got to capitalize on it.

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NASA’s budget is a budget ; that’s Gov’t allocation. No market is apart of that.

Aerospace is a hot market right now, because SpaceX lit everyone’s imagination on fire as to what could be done in it.

There are over 100 Rocket Startups, and they were increasing during 2020. VCs are jumping over themselves to find the “next SpaceX”.

So thank God, NASA is not the End-all-be-all for Aerospace any longer. Were steadily getting away from the monopsonistic model.


Scott Manley talks about the boosters there, and other re-used shuttle components.

I’m not going to dispute your overall point, (and the shaking is something that I’m not knowledgeable about), but as I mentioned, adjusting thrust can still be done with the liquid fueled central stage even with the solid fuel parallel boosters.

As to recovery, they nearly always recovered the SRBs on from the shuttle missions, so it can be done, even if they didn’t decide to do so in this case.

Separate: On the Space-X Super Heavy booster, a video I saw said that the plan was to turn it around and land it back at the launch site. This strikes me as a singularly inefficient way of doing things in terms of payload/cost, as compared to landing the booster downrange. Are they doing it that way? If so, why?

For that matter, why are they doing liquid methane instead of RP-1, when they used the latter on the Falcon 9 not only for the first stage, but also the second (which surprised me, since they couldn’t do it with the Saturn IB and Saturn V; I assume because of problems with the fuel freezing in space)? I know that LH is superior to RP-1 for total impulse to weight ratio, but it’s vastly inferior in terms of total impulse to volume, to the point where the extra weight and drag to contain the larger volume of fuel more than offsets the fuel weight advantage; and I’m guessing that liquid methane is worse.

But not cost effectively. It’s cheaper to rebuild them from scratch than to fish the empty steel castings from the sea, refurbish and refill them.

SRBs oscillate the payload; the shuttle SSMEs did not fix this. They literally had to invent a display that could counter-oscillate so that it was still readable to the astronauts while everything was shaking.

Oscillation is half the reason the payload I worked on, Europa Clipper, is not going on SLS as the law required. The other reason being an SLS rocket won’t be available in time to launch it.

Finally, SRBs are unsafe. You don’t control them so much as point them in a general direction and fire.

You can shutoff, redirect, refire liquid engines. Solid boosters leave far less options to save the crew in the event of an emergency. If they get out of control, your only recourse is to blow them up.

  1. They do both, you see that with Falcon. They’re building larger mobile launchpads / catching vehicles as we speak from mobile oil derricks.

  2. Rocket Lab is not doing this, and they argue it’s because the investment creating and operating a sea platform is overhead they don’t want.

Extra performance is good, but it can be bad if it ruins turnaround, or your cost structure. You have to decide if it’s worth it. Sometimes, even SpaceX decides it’s not.

Coking (so harder to clean = slower turn around, less lifetime engine reuse), less energy dense, burns at a cooler temperature…

And finally, you can make Methane on the moon and Mars. You cannot make Kerosene.

However, for strictly earth applications you do have a company, run by SpaceX’s former head propulsion engineer, using Kerosene. Firefly Aerospace.

I don’t think that was the problem.

Outside of LEO, Kerosene engines underperform compared to hydrogen upper stages. Delta IV outperforms Falcon Heavy going to GEO, or deeper into space for this reason.

I hadn’t thought in terms of a sea-mobile platform, although I guess that could make sense. I was thinking more in terms of a downrange island where they could land it and ship it back. Even if it weren’t in the perfect spot, it wouldn’t use nearly as much of the booster’s total impulse as it would to return to point of departure.

Okay, I guess that explains methane vs. RP-1. But what about methane vs. hydrogen? Is it any better for total impulse vs. weight and/or volume? It seems to me that it would be even easier to produce hydrogen on Mars than methane.

Okay, one point: Why only beyond LEO? Vacuum is vacuum, whether it’s in LEO, or halfway to M-31. Wouldn’t it more likely be a matter of atmospheric vs. extra-atmospheric?

That would limit what inclinations they can target. Also, most of the islands down range from Florida, far enough to be used like this, don’t belong to the U.S.

But, they’re building a Launchpad in Indonesia, maybe they’re thinking about doing this.

It’s hard to make, harder to store long term (smaller molecule), harder to launch due to the larger size of the tanks both due to the volume and the extra insulation you need, and there’s a wider temperature gradient between Hydrogen and Oxygen. It’s about 70-100C degrees.

The temp gradient between Methane and Oxygen is only about 10C.
Methane also burns cooler, so while you take an efficiency hit, it’s a better choice for a reusable system.

Even ULA has switched to a methane engine 1st stage for Vulcan.

Ah I correct myself; a fully expendable Falcon Heavy has better performance than the Delta Heavy or Atlas V to GEO.

What the Falcon Heavy suffers in is exceeding escape velocity to travel to destinations beyond Earth influence:

And this is simply because Kerosene is less efficient. Higher thrust-to-weight, so it punches out of the atmosphere faster, with slimmer tanks, so it initially has the advantage.

burns longer, lower flash point, add nitrates for lower loss. How many of these do we have forward deployed to Nuke Russia all spacecraft at this point to me is how many do we have and how fast can we end this nightmare?


Falcon would make for a lousy ICBM.

Solid rocket motors is what we use.

Not liquid rockets, solid rockets. Not Kerosene, not liquid anything, solid aluminum and ammonium perchlorate.

The latter requires less maintenance, and you can fire them at a moments notice.

That’s what both Trident missiles are on the Ohio-class, that’s what Tomahawk missiles use, that’s what the Minutemen III uses.

Falcon had no role here. At best, they’re putting up new satellites to watch what’s happening.

Wow. There’s some nitty gritty in here that I never imagined. I didn’t realize that methane had more total impulse per volume.

I assume you mean higher thrust-to-weight for the whole stage; I understood that at least compared to hydrogen, the total impulse-to-weight ratio for the fuel alone favored hydrogen over RP-1.