Author Topic: Fly Me to the Moon on an SLS Block II  (Read 10154 times)

Offline Steven Pietrobon

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Fly Me to the Moon on an SLS Block II
« on: 07/20/2015 01:33 AM »
Today is the 46th anniversary of Apollo 11 landing on the Moon.

Attached is a paper I have written of how a Block II configuration of SLS can be used to return humans to the Moon in a single launch. If you feel you are not proficient enough in mathematics, I suggest only reading the Introduction and Conclusion of the paper. The abstract is below.

"We examine how a 140 t to low Earth orbit (LEO) Block II configuration of the Space Launch System (SLS) can be used to perform a crewed Lunar landing in a single launch. We show that existing RSRMV solid rocket motors can be used to achieved Block II performance by using a core with six RS–25E engines and a large upper stage (LUS) with two J–2X engines. A cryogenic propulsion stage (CPS) with four RL–10C–2 engines is used to perform trans Lunar injection (TLI), Lunar orbit insertion (LOI) and 75% of powered descent to the Lunar surface. A Lunar module (LM) initially carrying two crew and 535 kg of cargo is used to perform the remaining 25% of Lunar descent. The LM is in two parts consisting of a crew and propulsion module (CPM) and non–propulsive landing and cargo module (LCM). The CPM returns the crew and 100 kg of samples to the waiting Orion in Lunar orbit for return to Earth."
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline Oli

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Re: Fly Me to the Moon on an SLS Block II
« Reply #1 on: 07/20/2015 03:09 AM »
That's nice and all, but I hope you realize there is literally zero chance any of this is going to happen?

Absolute no-gos as far as I can tell:
- That kind of effort for 14-day lunar sorties (been there, done that!)
- 6-engine core.
- LUS with J-2x and common bulkhead.

Just saying, lots of talent being wasted here  ;)
« Last Edit: 07/20/2015 03:09 AM by Oli »

Offline Steven Pietrobon

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Re: Fly Me to the Moon on an SLS Block II
« Reply #2 on: 07/20/2015 03:38 AM »
If you believe the universe is infinite, then there is 100% chance that this will occur, but most likely not here. :-)
« Last Edit: 07/20/2015 04:20 AM by Steven Pietrobon »
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline ciscosdad

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Re: Fly Me to the Moon on an SLS Block II
« Reply #3 on: 07/20/2015 04:21 AM »
Thanks Steven.
This type of study is exactly why I'm at Nasaspaceflight. We're here because we're dreamers, not because we think something can't or won't happen. The more exercises like this that you and any of our other resident experts can do, the better for all of us, if only for the education into what is possible.

Well done. I intend to read it from front to back several times, and I will be much better informed as a result.

Offline Oli

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Re: Fly Me to the Moon on an SLS Block II
« Reply #4 on: 07/20/2015 07:01 AM »

Ok my first post wasn't very constructive. Something else:

You assume SLS 1B with EUS can insert ~26t into LLO, approx. the same as Orion (I remember seeing numbers up to 30t (?) elsewhere..). Shouldn't a lander of such size be capable of delivering significantly more mass to the surface than your solution? For a quick sortie that may not matter, but if you want to build and resupply an outpost...

IMO 2 SLS 1B are only wasteful if you cannot utilize their performance entirely.

Offline MP99

Re: Fly Me to the Moon on an SLS Block II
« Reply #5 on: 07/20/2015 08:08 AM »


IMO 2 SLS 1B are only wasteful if you cannot utilize their performance entirely.

ISTM one of the issues with SLS is that the flight rate is critically low to keep the ground crews fighting fit.

At some point it makes sense to stop spending money on development, and instead spend it on building rockets and flying missions. Which I think is the point of block 1B.

Downside is that two widely spaced launches with LEO rendezvous has major boiloff issues. LOR and a lander with storable prop seems to me to be the method which requires the least development money to implement.

Cheers, Martin

Offline RocketmanUS

Re: Fly Me to the Moon on an SLS Block II
« Reply #6 on: 07/20/2015 04:52 PM »
First off this paper is a tribute to the 46th anniversary of the Apollo Lunar landing. This paper shows there is still interest in crew missions to the Earth moon. I believe it best if commercial were to take over from here and NASA buy rides to the moon for it's science missions.

1 ) Added cost to develop when the U.S. needs the funds for another launch vehicle for national needs.

2 ) Low flight rate ( brain drain )

3 ) Missions would be going on in early 2030's when nation was to be heading to Mars ( crew missions )

However it could have two launchs a year. One cargo and the other crew.

11 launches, first a test flight and the other 10 missions to Lunar surface.

Cargo landings could be a Hab with wheels. Could travel to another site by Earth remote control between missions. Another cargo landings could bring rover, science equipment, added food water for extended stay, ect.
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Offline msat

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Re: Fly Me to the Moon on an SLS Block II
« Reply #7 on: 07/21/2015 03:28 AM »
@RocketmanUS

While I somewhat agree that NASA should try to avoid "building" rockets, what commercial options do they have for the payload mass they're talking about? Should they wait for SpaceX's BFR? What happens if it doesn't come to fruition, and if it does, what kind of political fallout would ensue in the event that it's a failure? Besides that, they have no other options.

While I do think the SLS is unwarranted for the time being as it doesn't even have any definitive missions, nevermind the extreme cost, I do understand why NASA wants to design a rocket to their spec (and of course you have some in congress demanding it). Sure, they could pour that money in expediting BFR development, but there would be [somewhat understandable] cries coming from all corners of aerospace and government regarding such subsidies of one company, and I doubt SpaceX would want to share development with anyone else on that project.

Offline RocketmanUS

Re: Fly Me to the Moon on an SLS Block II
« Reply #8 on: 07/21/2015 04:27 AM »
@RocketmanUS

While I somewhat agree that NASA should try to avoid "building" rockets, what commercial options do they have for the payload mass they're talking about? Should they wait for SpaceX's BFR? What happens if it doesn't come to fruition, and if it does, what kind of political fallout would ensue in the event that it's a failure? Besides that, they have no other options.

While I do think the SLS is unwarranted for the time being as it doesn't even have any definitive missions, nevermind the extreme cost, I do understand why NASA wants to design a rocket to their spec (and of course you have some in congress demanding it). Sure, they could pour that money in expediting BFR development, but there would be [somewhat understandable] cries coming from all corners of aerospace and government regarding such subsidies of one company, and I doubt SpaceX would want to share development with anyone else on that project.
For Lunar missions I was referring to Vulcan/ACES ( cost to develop SLS block II from the paper could fund Vulcan/ACES ). There is no commercial option that I know of ( including BFR as we have no public specs or know if it has full funding ).

SLS can only launch one at a time. It would still need to place payload in LEO if it were to send two crew creaft to Lunar orbit for safety ( from t/Space concept ). Yes they can use the lander as a life boat, but if Orion is damaged to badly for Earth reentry then crew could be lost. Vulcan/ACES offers the two craft option with much higher flight rates. All parts are light enough that a Vulcan can take it to LEO staging point. If we invested in Vulcan/ACES it is for other than crew BLEO exploration , that is a bonus. We don't know if we will see funding for missions to Lunar or other BLEO missions. So Vulcan/ACES can do the job if needed and there is funding, it is designed to handle the needed launches, unlike SLS block I/II.

Steven did a good job with his paper and use of SLS block II for a single Lunar launch mission. However we are ready for the next steps for BLEO crew misions. That will take commercial to see Lunar return. Unless there is a payload that Vulcan or Falcon heavy can't handle I don't see this happening, just to much money to repeat Apollo with a little longer stays. Plus SLS could only launch twice a year and that would use up all SLS flight for five plus years for the eleven missions just for Lunar.

So what do you think of the Lunar missions in the paper and what do you like ( lander, ascender ect. )?
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Offline Steven Pietrobon

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Re: Fly Me to the Moon on an SLS Block II
« Reply #9 on: 07/21/2015 07:00 AM »
Shouldn't a lander of such size be capable of delivering significantly more mass to the surface than your solution? For a quick sortie that may not matter, but if you want to build and resupply an outpost...

I haven't crunched the numbers, but I would expect a dual Block IB mission to be able to land more cargo. Afterall, you are putting 186 t into LEO compared to 140 t.

Downside is that two widely spaced launches with LEO rendezvous has major boiloff issues. LOR and a lander with storable prop seems to me to be the method which requires the least development money to implement.

That's right. In a dual Block IB mission, the Lunar lander using storable propellants would be sent first to wait in LLO for Orion, so there are no boiloff issues.
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline the_other_Doug

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Re: Fly Me to the Moon on an SLS Block II
« Reply #10 on: 07/21/2015 04:17 PM »
...SLS could only launch twice a year and that would use up all SLS flight for five plus years for the eleven missions just for Lunar.

Just a slight clarification -- they can only, at this time, make two SLS boosters a year.  If several are made up in advance, the latest thinking is that they could be launched every 120 days in "salvo" mode, meaning with present construction and launch flow capability, they could launch three a year.  And if a program was funded that required a higher flight rate, assuming you could make enough of them, you could increase that flight rate to up to five or six launches a year, based on the capability proven during Apollo to be able to launch every 60 days off of one pad.  (Yes, they did ease their constraints somewhat by launching Apollo 10 from 39B, but could easily have kept to the same launch schedule and only used 39A if they had chosen to do so.)
-Doug  (With my shield, not yet upon it)

Offline RocketmanUS

Re: Fly Me to the Moon on an SLS Block II
« Reply #11 on: 07/21/2015 06:32 PM »
...SLS could only launch twice a year and that would use up all SLS flight for five plus years for the eleven missions just for Lunar.

Just a slight clarification -- they can only, at this time, make two SLS boosters a year.  If several are made up in advance, the latest thinking is that they could be launched every 120 days in "salvo" mode, meaning with present construction and launch flow capability, they could launch three a year.  And if a program was funded that required a higher flight rate, assuming you could make enough of them, you could increase that flight rate to up to five or six launches a year, based on the capability proven during Apollo to be able to launch every 60 days off of one pad.  (Yes, they did ease their constraints somewhat by launching Apollo 10 from 39B, but could easily have kept to the same launch schedule and only used 39A if they had chosen to do so.)
More than three a year, very unlikely! But three launches is needed to help the brain drain.

What are the goals for these 11 crew landings?

The goals could be done by teleoperated rovers. Samples could be sent back if wanted by a t/Space like capsule. Atlas V and or Falcon heavy ( might need two launches, one EDS the other lander ) could send these landers to the Lunar surface. Just the development cost for SLS block II would pay for the launches, landers and some of the mission cost. The launch and missions cost if using SLS block II would pay for Vulcan/ACES development. So for the total investment of SLS block II and the 11 missions we could have 10 to 11 robotic Lunar missions plus Vulcan/ACES development. Robotic can cover more ground. So what is the better invetment? Crew can be sent latter if wanted. And ULA's 2009 paper on ACES for Lunar also has opening plans for ACES Mars.

With robotic missions not loss of crew risk. If the is a LOM it is not a big deal and we can move on without a big deal. Using existing commercial launch vehicles we would not be commited to 6 to 11 missions with a big development cost to justify. By the time the first 6 robotic missions could be launched ACES/Orion could be ready to send crew. We need to build our needed infrastructure to handle(modern crew BLEO missions ( not Apollo demonstration we can do it mission of the 1960's ). We need to have the ability to routinely send crew BLEO, not just once in a while. If Saturn Apollo program had continued it would have needed to evolve, lower cost , less risk, fast launch rates for crew and cargo.
« Last Edit: 07/21/2015 07:00 PM by RocketmanUS »
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Offline Nilof

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Re: Fly Me to the Moon on an SLS Block II
« Reply #12 on: 07/23/2015 09:49 AM »
I had some fun making the rocket described in KSP with Realism Overhaul installed, since this looks like a quick and fun mission to try out. I made a baseline 5seg SRB + six SSME core + 2 J2-X LUS configuration using the tank sizes outlined in your pdf.

On my first try, I got a 157 ton payload consisting of an almost full EUS (~150 m/s circularization delta-v used)  and some lead ballast to a 233 x 290 km orbit at 28.68 degrees inclination. Looks like there's quite a lot of margin in the design. One thing which may have increased the payload is a slightly higher thrust profile on the SRB's with a 95 second burnout time rather than 128 seconds. This may have reduced gravity losses and increased payload. The FAR atmosphere model in the modpack is great but may have underestimated the drag losses.

I'll enact the full mission in KSP and post a video of it on youtube in a few days.
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline Steven Pietrobon

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Re: Fly Me to the Moon on an SLS Block II
« Reply #13 on: 07/24/2015 05:46 AM »
Looking forward to that. Note that you need to get into a 32.55 degree orbit for initial Lunar missions.
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline MP99

Re: Fly Me to the Moon on an SLS Block II
« Reply #14 on: 07/24/2015 08:03 AM »


Shouldn't a lander of such size be capable of delivering significantly more mass to the surface than your solution? For a quick sortie that may not matter, but if you want to build and resupply an outpost...

I haven't crunched the numbers, but I would expect a dual Block IB mission to be able to land more cargo. Afterall, you are putting 186 t into LEO compared to 140 t.

Dual block 1B (RSRMV + EUS with RL10C) would be 210-225t to LEO, and ~80t through TLI.

Cheers, Martin

Offline RocketmanUS

Re: Fly Me to the Moon on an SLS Block II
« Reply #15 on: 07/24/2015 07:05 PM »
What would one SLS block IB get through TLI?

So could it get Orion into LLO?
Could it get Steven's Lunar lander to Lunar surface? If so then could get rovers ( probe ) before crew landings and test out the lander.

On descent to Lunar surface were is the CPS attached to the Lunar lander ( top or bottom )?
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Offline MP99

Re: Fly Me to the Moon on an SLS Block II
« Reply #16 on: 07/24/2015 07:59 PM »




Shouldn't a lander of such size be capable of delivering significantly more mass to the surface than your solution? For a quick sortie that may not matter, but if you want to build and resupply an outpost...

I haven't crunched the numbers, but I would expect a dual Block IB mission to be able to land more cargo. Afterall, you are putting 186 t into LEO compared to 140 t.

Dual block 1B (RSRMV + EUS with RL10C) would be 210-225t to LEO, and ~80t through TLI.

Cheers, Martin

Dual block 1B ...~80t through TLI.

Divide by two.

~40t through TLI.

Cheers, Martin

Offline Steven Pietrobon

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Re: Fly Me to the Moon on an SLS Block II
« Reply #17 on: 07/25/2015 06:36 AM »
Dual block 1B (RSRMV + EUS with RL10C) would be 210-225t to LEO, and ~80t through TLI.

Including the dry mass of the EUS, total payload is 210 t to LEO and 102 t to TLI. Data from

B. Donahue and S. Sigmon, The Space Launch System capabilities with a new large upper stage," AIAA Space Conf. and Exhib., San Diego, CA, USA, Sep. 2013.

What would one SLS block IB get through TLI?

Not including the EUS, payload is 39 t. Including the EUS, payload is 51 t.

Quote
So could it get Orion into LLO?

Yes, no problem.

Quote
Could it get Steven's Lunar lander to Lunar surface? If so then could get rovers ( probe ) before crew landings and test out the lander.

You would use a large Apollo type lander using storable propellants. Rovers and payloads would be stored in the triangular payload compartments in the descent stage.

Quote
On descent to Lunar surface were is the CPS attached to the Lunar lander ( top or bottom )?

You can't use the EUS, as the Lander would be waiting for several months in LLO for Orion to arrive. All its propellant would boiloff.
« Last Edit: 07/25/2015 06:37 AM by Steven Pietrobon »
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline RocketmanUS

Re: Fly Me to the Moon on an SLS Block II
« Reply #18 on: 07/26/2015 04:10 AM »
What would one SLS block IB get through TLI?

Not including the EUS, payload is 39 t. Including the EUS, payload is 51 t.

Quote
So could it get Orion into LLO?

Yes, no problem.

Quote
Could it get Steven's Lunar lander to Lunar surface? If so then could get rovers ( probe ) before crew landings and test out the lander.

You would use a large Apollo type lander using storable propellants. Rovers and payloads would be stored in the triangular payload compartments in the descent stage.

Quote
On descent to Lunar surface were is the CPS attached to the Lunar lander ( top or bottom )?

You can't use the EUS, as the Lander would be waiting for several months in LLO for Orion to arrive. All its propellant would boiloff.
So SLS block IB could get an Apollo style LEM on the Lunar surface with about 50% increase in payload mass ( cargo ) or a 3 crew ascender?

A hypergolic fueled lander can wait in LLO for Orion/Crew. No CPS for descent needed.

For your SLS block II were is your lander attached to the CPS on descent to Lunar surface ( on the landers bottom or top?

So why develop block II if not needed for Lunar? Block IB could deliver great payload mass to the Lunar surface and more crew. For cargo only block IB is better sized. For the same amount of missions development and launch cost would be about the same. If a larger HLV is needed for Mars or other in the future then we could develop what is needed then.

Edit:
Launch 1: SLS block IB with Orion/Lunar lander
Launch 2: SLS block IB EDS

Connect Orion/Lunar lander and EDS in LEO. Then TLI burn.
Possible option.
« Last Edit: 07/26/2015 04:14 AM by RocketmanUS »
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Offline Steven Pietrobon

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Re: Fly Me to the Moon on an SLS Block II
« Reply #19 on: 07/28/2015 09:25 AM »
So SLS block IB could get an Apollo style LEM on the Lunar surface with about 50% increase in payload mass ( cargo ) or a 3 crew ascender?

It might be possible to do both.

Quote
For your SLS block II were is your lander attached to the CPS on descent to Lunar surface ( on the landers bottom or top?

The lander is attached to the top of the CPS. See Figure 8 in the paper.

Quote
So why develop block II if not needed for Lunar?

That's what Congress wants. If the aim is Block II, then that is what should be developed. Once developed, it can be flown in a Block IB configuration if desired.
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline MP99

Re: Fly Me to the Moon on an SLS Block II
« Reply #20 on: 08/01/2015 09:52 AM »
Quote
So why develop block II if not needed for Lunar?

That's what Congress wants. If the aim is Block II, then that is what should be developed. Once developed, it can be flown in a Block IB configuration if desired.

Block 1B would mean going back to using RSRMVs, which I think is unlikely.

I think the config with EUS and advanced boosters, but without LUS (which I assume you meant) would be better called Block 2B.

Cheers, Martin

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Re: Fly Me to the Moon on an SLS Block II
« Reply #21 on: 09/07/2015 09:34 PM »
@RocketmanUS

While I somewhat agree that NASA should try to avoid "building" rockets, what commercial options do they have for the payload mass they're talking about? Should they wait for SpaceX's BFR? What happens if it doesn't come to fruition, and if it does, what kind of political fallout would ensue in the event that it's a failure? Besides that, they have no other options.

While I do think the SLS is unwarranted for the time being as it doesn't even have any definitive missions, nevermind the extreme cost, I do understand why NASA wants to design a rocket to their spec (and of course you have some in congress demanding it). Sure, they could pour that money in expediting BFR development, but there would be [somewhat understandable] cries coming from all corners of aerospace and government regarding such subsidies of one company, and I doubt SpaceX would want to share development with anyone else on that project.

Why do you assume that Commercial option means that NASA's budget doesn't pay for any of the hardware development?   With the COTS development contracts we have seen both Private and Public money being put in to develop the hardware that NASA needs.  You could save development money by simply moving away from Cost-Plus contracts to Fixed Cost contracts still using FAR regulations.  We don't need a cost-plus contract to develop a HLV, there isn't that many unknown-unknowns that a contractor cannot adequately plan for the development risks. 
"Look at that! If anybody ever said, "you'll be sitting in a spacecraft naked with a 134-pound backpack on your knees charging it", I'd have said "Aw, get serious". - John Young - Apollo-16

Offline Steven Pietrobon

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Re: Fly Me to the Moon on an SLS Block II
« Reply #22 on: 04/27/2017 06:40 AM »
I submitted my paper to the IAC congress being held in Adelaide this year. I got a reply today saying my paper was accepted!
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline carmelo

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Re: Fly Me to the Moon on an SLS Block II
« Reply #23 on: 04/27/2017 06:42 PM »
Thanks Steven!
You have answered to this my old question:

http://forum.nasaspaceflight.com/index.php?topic=42711.0

Yes,we can.

Offline Patchouli

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Re: Fly Me to the Moon on an SLS Block II
« Reply #24 on: 04/30/2017 04:35 PM »
I wonder how high risk would refueling the EUS be as that could greatly increase the TLI payload?

Another option if it's fully operational by then launch part of the hardware on a Falcon Heavy and do all staging of the mission in LEO vs L1.

I'm assuming that FH actually can lift 53 tons as that would be enough for an Altair class lander plus a few tons for a payload interface.
« Last Edit: 04/30/2017 04:37 PM by Patchouli »

Online TrevorMonty

Re: Fly Me to the Moon on an SLS Block II
« Reply #25 on: 05/01/2017 01:46 AM »


I wonder how high risk would refueling the EUS be as that could greatly increase the TLI payload?



If ULA's distributed lift proves successful then an upgraded EUS to support refuelling could be easy upgrade to SLS. Switching EUS to ULA flight proven (by then) IVF would be low risk upgrade with huge payload benefits.

Offline Steven Pietrobon

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Re: Fly Me to the Moon on an SLS Block II
« Reply #26 on: 07/21/2017 06:32 AM »
To celebrate the 48th anniversary of the first crewed landing on the Moon, here's the latest version of my paper. Updates are:

1) Changed the engine configuration of the LM. Now have a central fixed thrust and position engine in middle for ascent and abort (instead of two canted nozzles) and two variable thrust and position engines next to the ascent engine (instead of one engine).
2) The increased performance from the ascent engine (since it is no longer canted) allowed an increase of the boil off rate from 0.1% to 0.17% per day, with the cargo mass slightly decreasing from 535 to 509 kg.
3) Deleted the core engine configuration with five engines at the circumference and a central engine. Added a core engine configuration with two rows of three engines. This gives better spacing to the booster nozzles.
4) Deleted the six flight cost numbers. Added 29 flight cost numbers for SLS Block II and dual flight Block IB, which is the break even point where Block II becomes cheaper.
5) For Orion Block II, showed that this allows plane changes up to 12.1º with current service module. Cargo mass decreases from 3396 kg to 2296 kg.
« Last Edit: 07/21/2017 06:55 AM by Steven Pietrobon »
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline Steven Pietrobon

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Re: Fly Me to the Moon on an SLS Block II
« Reply #27 on: 07/21/2017 06:40 AM »
Michel Lamontagne from Canada has been doing some fantastic work on providing artwork of the launch and landing sequence. Here's some preliminary artwork to whet your appetite.
Akin's Laws of Spacecraft Design #1:  Engineering is done with numbers.  Analysis without numbers is only an opinion.

Offline MATTBLAK

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Re: Fly Me to the Moon on an SLS Block II
« Reply #28 on: 07/21/2017 06:47 AM »
That's awesome! :) I admit that most of the math in the paper is beyond my relatively igorant edumacation ;) I was once going to have professional artwork for my old Mars Mission paper - but I had to use my crude temp drawings instead! This gives your publication some extra class...
« Last Edit: 07/21/2017 06:56 AM by MATTBLAK »
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Offline Propylox

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Re: Fly Me to the Moon on an SLS Block II
« Reply #29 on: 07/22/2017 01:56 AM »
Today is the 46th anniversary of Apollo 11 landing on the Moon.

"We examine how a 140 t to low Earth orbit (LEO) Block II configuration of the Space Launch System (SLS) can be used to perform a crewed Lunar landing in a single launch. ...
Nicely done. Your dedication and detail is as impressive as successfully crafting a direct-to-landing mission. Not the path I'd take, but much respect is deserved and given.
I was quite surprised by your drymass of 123.6mT for the six-engine core as it seems exceptionally high.
« Last Edit: 07/23/2017 03:01 AM by Propylox »

Offline MATTBLAK

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Re: Fly Me to the Moon on an SLS Block II
« Reply #30 on: 07/22/2017 05:22 AM »
I too would prefer a single-launch Lunar mission like 'the good old days'. But forgive me if I missed anything at some stage: have you ever crunched the numbers for a Lunar mission done with dual launches of an SLS Block 1B or similar? I know that would be an expensive mission; though it should allow for a much bigger LM for pretty long stay times on the surface. Also; should allow cargo-only LM versions in single launches of a Block 1B.
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Offline Propylox

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Re: Fly Me to the Moon on an SLS Block II
« Reply #31 on: 07/23/2017 12:53 AM »
Here's some preliminary artwork to whet your appetite.

That's a whole lot of rocket for an Apollo "flags and footprints" redux. Heck, SLS is a whole lot of rocket anyways and that's a problem IMO. I previously asked about your excessive core stage's drymass of 123.6mT and your J-2X US at 16.9mT seems quite light. I started with different assumptions, resulting in different masses for each and a different, though just as capable rocket. If you'd allow me ..........


The J-2X US would be fabricated on the existing 8.4m LOX jig, composed of a 22ft barrel similar to that used for the core tank. With a common bulkhead separating propellants it holds 422,680 lbs. As you mentioned, the final propellant load may be a bit less depending on mission. Utilizing commonality with the core for manufacturing purposes, cost reduction and it's location atop the RSRM crossbeam;

It has a drymass of 20,440kg with 2x J-2x -or- 18,350kg with a single J-2X flanked by 2x RL10s
 -- Maximum capabilities BLEO is achieved if all three ignite at staging with J-2X cutoff after 500s. If propellant flow is an issue, the RL10s would instead ignite after the 500s J-2X burn - essentially becoming a combined 2nd/3rd stage with BLEO max payload now equivalent to the 2x J-2X US

After completing the US, the existing 8.4m LOX jig would begin manufacturing another 22ft barrel with common bulkhead. The existing SLS uses five barrels and a gigantic thrust structure for its H2 tank. Instead, the LOX tank should be a sixth 22ft barrel where the current thrust structure wastes space.
The 2nd common bulkhead manufactured replaces the #5 barrel, including internal buttressing to handle additional loads. It's likely the #6 LOX barrel will need to be manufactured on the 8.4m LOX jig with reinforcing spars. The new abbreviated thrust structure and RS-68s now sit flush to the LOX tank.

This core has a drymass of 81,700kg with 3x RS-68 + interstage + a boattail to modify the thermal environment -or- 70,250kg without an US, only 2x RS-68 and a payload adapted in place of the interstage - directly atop the RSRM crossbeam. The corestage holds 1,907,626 lbs propellant with assumptions on final internal volume and a 6:1 O/F ratio.
-- The O/F ratio and internal volume will change during development as will specific mission load so the 1.9 million lbs is a current estimate. Whether in single or two-stage configuration, the core lifts off at 60% throttle for the first ~2min and throttles down to 60% at 3g when the tank nears empty. With significantly less drymass and propellant, the extra thrust isn't needed at liftoff and propellant better used after solid separation


* I calculate a 2x RS-68 single stage will place 65mT to 75mT into a 210km LEO, depending on constraints.
* The 3x RS-68 will place +130mT into LEO with a 2x J-2X US -or- 40mt to 45mT into a 311,425km x 185km expedition orbit, depending on constraints.

Funding wise; The existing EUS and Advanced Booster programs would be cancelled and resources allocated to common bulkhead development, production and re-engineering the business-end of the SHLV. You proposed and outlined the importance of J-2X (as have I and others), but I'd also cancel the RS-25 program, switch AR's production contract to J-2X and use RS-68s on the core with almost no modifications.
« Last Edit: 07/23/2017 01:01 AM by Propylox »

Offline Steven Pietrobon

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Re: Fly Me to the Moon on an SLS Block II
« Reply #32 on: 07/23/2017 03:36 AM »
I too would prefer a single-launch Lunar mission like 'the good old days'. But forgive me if I missed anything at some stage: have you ever crunched the numbers for a Lunar mission done with dual launches of an SLS Block 1B or similar? I know that would be an expensive mission; though it should allow for a much bigger LM for pretty long stay times on the surface. Also; should allow cargo-only LM versions in single launches of a Block 1B.

There's a rough analysis of the dual Block IB architecture in the paper. A single launch is 20% cheaper per mission, but has a higher development cost due to needing to develop a new core and large upper stage. At 29 missions, total cost (development and mission) single launch becomes cheaper overall.
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Offline Steven Pietrobon

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Re: Fly Me to the Moon on an SLS Block II
« Reply #33 on: 07/23/2017 03:50 AM »
That's a whole lot of rocket for an Apollo "flags and footprints" redux. Heck, SLS is a whole lot of rocket anyways and that's a problem IMO. I previously asked about your excessive core stage's drymass of 123.6mT and your J-2X US at 16.9mT seems quite light. I started with different assumptions, resulting in different masses for each and a different, though just as capable rocket. If you'd allow me ..........

How I derived these masses is described in the paper. The Block I core dry mass is 100,062 kg, so I believe my value is in the right ball park for a six engine core. I derived my LUS mass from the Saturn V S-II, which has a 35,402 kg dry mass and 452,352 propellant mass.

Quote
Funding wise; The existing EUS and Advanced Booster programs would be cancelled and resources allocated to common bulkhead development, production and re-engineering the business-end of the SHLV. You proposed and outlined the importance of J-2X (as have I and others), but I'd also cancel the RS-25 program, switch AR's production contract to J-2X and use RS-68s on the core with almost no modifications.

I did not investigate using RS-68 since that would need to be redesigned so that the ablative nozzle (which won't survive the base heating conditions) is replaced with a regenerative nozzle, practically making it a new engine. That kills any saving from using a "cheaper" engine. This is the same mistake Griffin made when he replaced RS-25 with RS-68 on Ares-V.
« Last Edit: 07/23/2017 03:52 AM by Steven Pietrobon »
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Offline MATTBLAK

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Re: Fly Me to the Moon on an SLS Block II
« Reply #34 on: 07/23/2017 11:42 AM »
Yes. I'm afraid that RS-68 is just not going to get used in basically any context with the SLS. And if NASA was ever going to do a redesign of the Corestage I'd certainly hope it would be to incorporate 5 or 6 RS-25E's.
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Offline Propylox

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Re: Fly Me to the Moon on an SLS Block II
« Reply #35 on: Today at 02:16 AM »
I did not investigate using RS-68 since that would need to be redesigned so that the ablative nozzle (which won't survive the base heating conditions) is replaced with a regenerative nozzle, practically making it a new engine.
Not the place to debate that ...
... but I'd think someone who could develop and write such a proposal would also know better. Carry on  :-X
« Last Edit: Today at 02:17 AM by Propylox »

Offline MATTBLAK

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Re: Fly Me to the Moon on an SLS Block II
« Reply #36 on: Today at 01:08 PM »
He did know better?! That's why he didn't 'use' RS-68s in his proposal. Read about what happened in 'Constellation' history and you'll find out that NASA was in the process of changing back to RS-25s when Ares V/CXP was cancelled - NASA found that the base heating issue became unsolvable without regenerative nozzle engines. All this happened and was documented years ago. Do try to keep up...
« Last Edit: Today at 01:11 PM by MATTBLAK »
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