Kellymcdonald78 t1_j6p1j6u wrote

Research was most definitely not “done” for Orion. From miniature warheads, to a system capable of delivering them reliably, to the shock absorbers. It was a high level concept that was simply validated as an avenue of research with potential. Years of additional research and billions of dollars would be been needed to actually design and build an actual vehicle. It’s the difference between Robert Goddard’s experiments and the Saturn V


Kellymcdonald78 t1_j6bo3x2 wrote

Now you’re creating a strawman. I never claimed that the Falcon Heavy was equivalent to Block I SLS. I disputed your claim that it had 3 times the payload.

RS-25E is a completely new assembly line using new production methods and new engine controllers (as the original RS-25 hasn’t been built in decades)

BOLE (the new SRBs) use completely different casings (composite) and a new propellant mixture.

EUS is net new (but will be introduced for Block IA). Heck the mobile launch platform needed for Block 1A and Block 2 is having substantial issues. The only thing common, is the core tanks and thrust structure


Kellymcdonald78 t1_j6bjvpz wrote

Yes, I said hypothetical to both. Either you compare the vehicles that are flying today or you compare hypothetical vehicles from 4-5 years in the future.

In either scenario SLS IS NOT carrying 3 times the payload of its competition.

BTW Block II will have completely new SRBs, a new upper stage and a new version of the RS-25. Hardly “80%-90%” of what was used on Artemis I


Kellymcdonald78 t1_j6bh5ms wrote

As I said, let’s assume your numbers are correct. 16,000kg for TLI for Falcon Heavy. SLS Block I is 28,000kg TLI. That IS NOT 2-3 times the performance of Falcon Heavy. (Twice is 32,000kg which is greater than 28,000kg).

However if you’re going to start comparing what the hypothetical future SLS performance might be in 4-5 years, then expect to compare it against what the hypothetical future SpaceX performance might be in 4-5 years which will be Starship and Superheavy. Falcon Heavy likely won’t even be flying by 2027


Kellymcdonald78 t1_j6bd8ed wrote

SpaceX doesn’t currently publish their TLI payload so I’m not sure what you want them to “update”

Plus the SLS Block IB won’t even fly until 2027 (at the earliest) and that will be the crew version which has a lower payload of 38,000 kg to TLI. So while that version will be more than twice the payload of Falcon Heavy (using your numbers), it will be competing against Starship and Superheavy by then


Kellymcdonald78 t1_j6aw1is wrote

Falcon 9 performance has continued to improve since 2018. However, let’s go with the 16,000kg number, SLS block 1 still doesn’t have 3 times the payload to TLI, it doesn’t even have twice the payload. We’ll likely get block IB, but it’s unclear if block 2 will ever get funded.


Kellymcdonald78 t1_j6aiipl wrote

You said SLS is rad hardened not Artemis (Artemis isn’t even a vehicle, it’s a programme). Orion is “rad hardened” but except for the second stage, SLS doesn’t even leave LEO.

I’ve read the SpaceX submission. They’ve made a few changes to help reduce crew impact in the event of a CME, but the electronics are not rad hardened (radiation hardened CPUs and memory don’t have the performance SpaceX needs)

You also said that Commercial Crew gets an “exemption” because of they’re “short LEO missions”. Hint: they aren’t short


Kellymcdonald78 t1_j6advot wrote

And 16,800 to TMI (Trans Mars Injection). Folks who’ve done the delta V analysis puts the Falcon Heavy TLI performance at approximately 20,000kg

There is no part of SLS that enters into a “high rad” environment except the second stage and for Block I it’s a stage they’ve taken from Delta III. Please let me know exactly what is “rad hardened” on SLS

As well, system redundancy is the exact same method used on Starship, both as part of the Artemis program (as the lunar lander) and potential Mars missions. Crew Dragons are kept on ISS for months, they aren’t exactly “short duration missions”


Kellymcdonald78 t1_j69utue wrote

SLS isn’t rad hardened. The only part that even leaves LEO is the ICPS and that’s just taken from the Delta III.

Falcon Heavy in expendable mode has a TLI of about 20,000kg, SLS block I is about 27,000kg hardly 3 times.

Orion does have improved rad hardening, but Dragon solves that issue with multiple redundant systems to compensate for radiation induced bit errors. The same approach being used on Starship