Jump to content

[New] Space Launch System / Orion Discussion Thread


Recommended Posts

14 minutes ago, jadebenn said:

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

HLS1.jpg

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.

Link to comment
Share on other sites

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.

Link to comment
Share on other sites

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.

 

Link to comment
Share on other sites

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.

Link to comment
Share on other sites

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 by jadebenn
Link to comment
Share on other sites

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 by jadebenn
Link to comment
Share on other sites

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 by RCgothic
Link to comment
Share on other sites

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.

 

Link to comment
Share on other sites

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.

Link to comment
Share on other sites

 

Spoiler

Oy6zgcZ9Qt2-FS82WE3qdVpj6WXOK6lWKd73V2k8

 

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.

Link to comment
Share on other sites

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 by tater
Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...