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56 votes
Accepted

Why does the government still fund SLS while SpaceX is cheaper and has the same capabilities if not better?

It is still way too early to make such a judgement. It's easy to be overly optimistic about the cost of a program. The Space Shuttle was supposed to have dozens of flights each year and be super-...
DrSheldon's user avatar
  • 48k
38 votes
Accepted

How much of the second SLS has been built?

The Core Stage-2 is currently slated to be delivered in March 2023. It is mostly complete. Core Stage-3 is structurally complete and assembly of the engine section of Core Stage-4 has begun. The RS-25 ...
Jörg W Mittag's user avatar
33 votes
Accepted

What is a "Major Component Failure" referred to in news reports about the unsuccessful Space Launch System core stage test firing?

tl;dr Each engine reports a self-test status to the vehicle it's attached to. "MCF" is one of the possible statuses and indicates that the engine controller has detected a serious - but not ...
Organic Marble's user avatar
33 votes
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When Artemis runs out of rollbacks

You wrote [bold emphasis mine]: It was reported that NASA managers have said the system is rated for two more rollbacks to the VAB, so after this hurricane decision it appears the stack will need to ...
Jörg W Mittag's user avatar
30 votes

Do the solid rocket boosters of the Shuttle and SLS have a self-destruct system and was it activated during the Challenger disaster?

The shuttle stack broke up at ~73 seconds after launch of STS-51L. The Solid Rocket Boosters separated from the other elements and continued flying in a more or less stable manner (surprisingly). ...
Organic Marble's user avatar
26 votes
Accepted

What is the purpose of the aft skirt on the Space Shuttle and SLS Solid Rocket Boosters?

Main points about the SRB aft skirt are that they: bear the entire weight of the launch vehicle, prelaunch had (SLS SRB does not) four hold-down/support posts distributed the loads between the SRB ...
blobbymcblobby's user avatar
26 votes
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How feasible is a manned flight to Apophis in 2029 using Artemis or Starship?

There's no point in a flyby since there would be no time to conduct any meaningful measurements. According to Wikipedia, 99942 Apophis will be going about 7 km/s relative to Earth at closest approach ...
Scott McPeak's user avatar
  • 1,209
25 votes
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Why won't the SLS boosters be recovered?

The usual answer - $. Booster recovery was only marginally worth it for STS - once you witnessed how every screw and nut was taken apart, cleaned, and reassembled, you began to wonder why not just ...
Organic Marble's user avatar
24 votes

Why not crash the ICPS into the Moon?

The upper stage for Apollo 8 through Apollo 12 were sent into heliocentric orbit. On the last five flights, Apollo 13 through Apollo 17, the upper stages were instead intentionally crashed into the ...
David Hammen's user avatar
22 votes
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Why isn't the Delta IV Heavy ever used for crewed spaceflight?

What's the reason that they don't use the Delta Heavy for crewed flights to the Moon and beyond? The Delta IV Heavy isn't powerful enough to send Orion beyond low Earth orbit. Orion masses about 26.5 ...
Russell Borogove's user avatar
20 votes
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Black/White patterns on SLS boosters, fairings - Are these still roll patterns

These patterns are used for tracking much more than just roll. According to this 2017 article from The Planetary Society, they will be used by tracking cameras to precisely measure the vehicle's ...
Camille Goudeseune's user avatar
19 votes
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Will SLS be launched as often as the space shuttle was?

Given the available data, no. Ignoring details like the lengthy stand-downs after the two loss-of-crew-and-vehicle shuttle mishaps, a naive calculation (135 launches between 4/12/81 and 7/8/11) gives ...
Organic Marble's user avatar
18 votes

When Artemis runs out of rollbacks

Partial answer to What constrains how many rollbacks Artemis can endure? A big part of it is resonant vibration (due to the crawler) causing fatigue to various and sundry parts of the SLS. You can ...
Organic Marble's user avatar
16 votes

What are the differences between SLS and Ares V?

As it turns out, SLS is actually very similar to the original Ares V configuration, proposed around 2002 (I believe). During this time it was known simply as 'CaLV,' or Cargo Launch Vehicle, as a ...
Alastair Haslam's user avatar
15 votes

Why does the government still fund SLS while SpaceX is cheaper and has the same capabilities if not better?

Eh, to begin with this statement isn't accurate. SpaceX ... has the same capabilities if not better? Falcon Heavy as stands can't replace SLS and launch Orion on the required orbit without ...
Barry Jenakuns's user avatar
15 votes

Will SLS be launched as often as the space shuttle was?

Your question is based on Wikipedia's description of this as "successor to the retired Space Shuttle". This statement is so severely flawed as to be basically untrue. The Shuttle was ...
Graham's user avatar
  • 1,920
14 votes
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How can Artemis 1 take so much longer for Earth-Lunar transit than the Apollo missions did?

The goal of the Apollo missions was to land humans on the Moon and return them to Earth. That requires a surprisingly large delta-V capability. (In terms of delta-V, is easier to land a vehicle on ...
David Hammen's user avatar
14 votes
Accepted

Does the SLS mobile launch platform share any hardware with STS or even Saturn I/V MLP?

The two-story gray platforms at the base were originally built for Apollo, modded for shuttle, and now modded again for SLS. The towers are new and suffered a lot of cost and schedule issues. Most of ...
Organic Marble's user avatar
13 votes

Why doesn't NASA plan a manned Venus flyby first?

A Venus flyby does little to nothing towards the stated goal: a manned landing on Mars. because you get a lot closer to the Sun than on a Mars mission, you need to modify the spacecraft to reject ...
Hobbes's user avatar
  • 128k
13 votes

Why does the government still fund SLS while SpaceX is cheaper and has the same capabilities if not better?

All the answers are right in their own way. One thing that is not addressed: The Falcon Heavy is not even remotly on par with the SLS in terms of rocket diameter and payload mass. According to ...
CKA's user avatar
  • 546
13 votes
Accepted

What do the banana values mean in this tweeted plot of heavy lift vehicle capabilities?

For most of the vehicles there seems to be a correlation between size and "banana number", which is not yet a SI-recognized unit of measure (And I really hope they don't decide to keep a ...
asdfex's user avatar
  • 15.1k
12 votes

Why will SLS Block I bring less mass to LEO than the STS shuttle system did?

It's always difficult to make apples-to-apples comparisons between the space shuttle and other launchers, because the orbiter is ambiguously part launcher and part payload. This is compounded by the ...
Russell Borogove's user avatar
12 votes
Accepted

What makes SLS (Space Launch System) \$10 Billion (or \$36 Billion) project?

Pork. It is a jobs program not a technology program. The SRB's are built by ATK, but the design ensured they needed to be reworked, so they could not just the existing Shuttle ones. Need an extra ...
geoffc's user avatar
  • 79.6k
12 votes
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What is the status of the F-1B engine development?

That project has been cancelled (or at least put on hold) as of June 2019. But NASA discontinued studies of upgrading the SLS, including study of reviving the F-1. Soon the testing of the F-1 gas ...
Organic Marble's user avatar
12 votes

Why does the government still fund SLS while SpaceX is cheaper and has the same capabilities if not better?

Part of it is leveling employment. The government is fond of large projects that require multi-year ramp-up and ramp-down and massive up/down swings in employment need. Suppose in 2019 you're hiring ...
Harper - Reinstate Monica's user avatar
11 votes

Could the solid boosters of SLS be replaced by reusable Falcon 9 first stages?

The SRBs for the Shuttle and SLS are used to get the stack moving and off the pad, so that the more efficient LOX/LH2 engines can do the hard work. In the case of the Space Shuttle, an amazing ...
geoffc's user avatar
  • 79.6k
11 votes
Accepted

RS-25 Hot Fire Test

The engine controller is a computer mounted on the SSME which monitors and controls the engine. It, for example, takes throttle commands as a % of power level from the vehicle and translates them ...
Organic Marble's user avatar
11 votes
Accepted

What does the software quality process for NASA's SLS look like?

I have retrieved via FOIA request the "Space Launch System Program (SLSP), Flight Software Application, Software Assurance Plan (SAP)". It is the core document describing the software development ...
Mark Omo's user avatar
  • 5,291
11 votes
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Why isn't NASA planning on saving some of the RS-25Ds due to their historical significance?

Many SSMEs are already displayed in museums. Stafford Air and Space Museum (theirs is taken apart and you can look in the pieces, very cool) Stennis Space Center National Air and Space Museum Space ...
Organic Marble's user avatar
10 votes
Accepted

Could the SLS reach orbit without solid rocket boosters?

Could the SLS block 1 reach orbit without solid rocket boosters, and if so, how much payload could it lift? Fully fueled, the first stage alone has only an 0.77:1 thrust-to-weight ratio; it can't ...
Russell Borogove's user avatar

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