[New] Space Launch System / Orion Discussion Thread

[tater]

14 minutes ago, jadebenn said:

You guys do realize what this news implies about the selection of the HLS lander, right?

Says it can do 41t to TLI.

That means a 2 or 3 stage lander is possible in one SLS Cargo flight. Constellation mission architecture, except LOR/LOR instead of EOR/LOR.

Still requires 2 SLS flights right after each other.

[Barzon]

1 hour ago, tater said:

Still requires 2 SLS flights right after each other.

Which is easily possible. We already have 2 MLs - one finished and one under construction. All that's needed is the relatively easy upgrade of High Bay 1 to support SLS stacking.

[Ultimate Steve]

How long would pad turnaround take for the SLS, and would that duration be a problem for cryogenics assuming the lander is cryo?

[RCgothic]

ML1 is configured for Block 1. It'll probably need expensive modifications once ICPS is retired.

Edited April 23, 2020 by RCgothic

[tater]

28 minutes ago, Barzon said:

Which is easily possible. We already have 2 MLs - one finished and one under construction. All that's needed is the relatively easy upgrade of High Bay 1 to support SLS stacking.

Possible, but not easily possible. Particularly given the proposed time frame.

The pad turn around would be one issue, then there is logistical planning around the flight. Would certainly require the lander use storable props, as you'd send the lander well ahead, then crew, and any weather issues on what would likely be a very tight launch window would be a huge issue. If the lander/launch was not super expensive, no big deal, but at billions a pop... not ideal.

This is a place where Gateway actually makes more sense vs avoiding Gateway, since the lander could dock there and wait. Windows would be easier vs an LLO (polar?) rendezvous.

 

[Barzon]

12 hours ago, tater said:

The pad turn around would be one issue,

IIRC Pad turnaround in STS was only a few weeks, so pad turnaround for 2 SLS would probably only be a month or so. 

[tater]

1 hour ago, Barzon said:

IIRC Pad turnaround in STS was only a few weeks, so pad turnaround for 2 SLS would probably only be a month or so. 

The point is the propellants I would think. That forces a hypergolic lander, since the lander is probably sent first, right?

Delays are always possible with launches, so the followup crew flight might happen in X weeks, but what is the window like? If they have to scrub, how many tries before they need to wait another month? Timing that way is less critical with a storable props for the lander, but if they use cryos it becomes an issue.

[jadebenn]

On 4/24/2020 at 6:27 AM, Barzon said:

IIRC Pad turnaround in STS was only a few weeks. 

More like a few days.

On 4/24/2020 at 7:47 AM, tater said:

Delays are always possible with launches, so the followup crew flight might happen in X weeks, but what is the window like? If they have to scrub, how many tries before they need to wait another month? Timing that way is less critical with a storable props for the lander, but if they use cryos it becomes an issue.

As long as you can get the timing below ~90 days (possible with SLS), there are some pretty high TRL technologies (especially with methane) you can use to mitigate this. From what I'm hearing from my friends on the other side, the two-stage SLS-launched design is actually the best shot at getting at a non-storable lander.

The three-stage alternative uses long ballistic transfers for each element due to the mass constraints, which means passive boiloff mitigation (the high TRL stuff) is not gonna cut it. So then you're talking about putting active in-space cryocoolers (low TRL, high power consumption) in an already extremely mass-constrained environment, and suddenly, just using some hypergols seems a lot more practical.

Edited April 26, 2020 by jadebenn

[kerbiloid]

Being ready for the risk of moonflight (~20 persons did it), but at the same time being afraid of hypergolic stages ( (tens?) millions of people were dealing with them) looks rather irrational.

[jadebenn]

They're not afraid of hypergols, there's just not a whole lot of good hypergol engines currently available for a lander, and it makes it harder to do an eventual transition to ISRU.

[RCgothic]

Once again the mission architecture trips over itself because SLS wasn't designed for sending a large lander to the moon as well as a large capsule.

[jadebenn]

2 hours ago, RCgothic said:

Once again the mission architecture trips over itself because SLS wasn't designed for sending a large lander to the moon as well as a large capsule.

Uh, you could fit a lander in the CPL available on SLS. It just wouldn't be one capable of meeting the much higher requirements for Artemis. 

NASA isn't interested in doing Lunar surface stays of less than a week. They've requested a design that can get them 2 crew for 7 days (more than 2x the longest Apollo stay) out of the box, and can go to 4 crew for 30 days with a small surface hab to take strain off the lander ECLSS. That means mass. Lots of it.

Edited April 26, 2020 by jadebenn

[RCgothic]

2 hours ago, jadebenn said:

Uh, you could fit a lander in the CPL available on SLS. It just wouldn't be one capable of meeting the much higher requirements for Artemis.

Yeah, I agree. An SLS can't do Artemis by itself.

Which leads to crazy things like the crew being sent on a gigantic crew-rated booster and the cargo being sent on smaller commercial vehicles. That's ass-backwards. 

Edited April 26, 2020 by RCgothic

[tater]

5 hours ago, RCgothic said:

Once again the mission architecture trips over itself because SLS wasn't designed for sending a large lander to the moon as well as a large capsule.

SLS wasn't designed with any particular mission in mind, that has always been the problem.

 

[tater]

 

[RCgothic]

Well. Here's hoping Boeing's analysis manages to get it right first time. That'd be nearly as big a bang as SN1 in a much more expensive test rig.

[Bill Phil]

On 4/26/2020 at 9:15 AM, tater said:

SLS wasn't designed with any particular mission in mind, that has always been the problem.

 

The entire selling point of SLS was that it offered heavy lift capability with "off the shelf" or "heritage" parts, and should thus have a shorter and cheaper development.

But there are problems with that. The tooling used for the Shuttle ET was disposed of, the SRBs had to completely redesigned, the DCSS has to be man-rated, and an entirely new upper stage has to be developed for later versions. The SLS is basically a completely new rocket compared to previous ones, and at this point it's being held back by the decision to use "off the shelf" hardware and existing engineering talent - the core geometry lends itself to high hydrostatic pressure at the engine inlets, the RL-10s don't have enough thrust, there are only enough SSMEs for four flights, etc. And of course there are the innumerable project management issues.

It's hardly an understatement at this point to say that a completely new rocket would probably have been a better choice. Either that or Shuttle-C with the five segment SRBs.

SLS won't offer any advantages from any point of view. It's a rocket to nowhere. The TLI throw weight is too low, but so is the LEO throw weight since it's optimized for high energy trajectories.

[sevenperforce]

2 hours ago, tater said:

 

Oh good god.

"One of the major risks anticipated in our test of this nuclear reactor is that it may trigger a chain reaction."

[tater]

Yeah, hydrogen will leak out of pretty much anything. Odd that it would not be anticipated and hence not a major schedule risk.

[tater]

 

[Flavio hc16]

45 minutes ago, tater said:

 

Can i say that the more i see stuff like this the more the sls sounds idiotc? It's like trying to swim meanwhile someone is stealing your money from your pocket and you have an iron ball attached to your leg....

[tater]

On 4/23/2020 at 2:02 PM, jadebenn said:

You guys do realize what this news implies about the selection of the HLS lander, right?

What?

Is the BO or Dynetics lander going on SLS?

[tater]

 

Spoiler

 

So we will get a value on SLS cost that "only" includes 400M$ in main engines, we won't ever see the billions to restart amortized into that, or the other billions spent to "refurbish" and "improve" the ones for the first flights, either.

[tater]

Eric did the math, and combined the billion+ to restart new RS-25 production (and 6 engines) with the new contract, so we get an accurate price per engine after the "cheap" 127 M$ each SSMEs are used up. They restarted production because they need the engines, and of course they can reduce the price since they don't need to be reused... by making them even more expensive. I guess they are cheaper since the SSMEs cost ~40M new, plus the 127M to refurb, so 146<167, right?

 

So not counting the SRBs, tanks, or anything else, each SLS costs $584,000,000.

Grrr.

Edited May 2, 2020 by tater

[.50calBMG]

And yet people still find ways to defend it