Author Topic: SLS Lander?  (Read 21767 times)

Offline A_M_Swallow

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Re: SLS Lander?
« Reply #20 on: 02/18/2018 11:28 pm »
{snip}
I should probably make it clear that I am not arguing against the use of L1/2 stations in the future.  Once Lunar sourced propellant is available in sufficient quantity, they make perfect sense.  I'm not trying to plan an inner solar system transportation network using existing Lunar propellant production capacity though.  What I am trying to understand is how DSG actually helps locating, then building, Lunar production capacity.  It would seem to me that it is hard to compete with LLO when SEP can replace ~25% of cargo lander chemical Dv using LLO.

I suspect that the DSG, or replacement e.g. Bigelow/ULA depot, will end up in LLO.

For the Moon base a Bigelow B330-MDS module would mass 20-30 tonnes. That is payload to the transportation system since the mass of the lander and propellant are additional to that.
https://en.wikipedia.org/wiki/B330

Offline Joseph Peterson

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Re: SLS Lander?
« Reply #21 on: 02/19/2018 12:30 am »

The DSG's Power and Propulsion Element (PPE) is a solar powered space tug. A second one can be used to push consumables like food, water and power from LEO to a spacestation orbiting the Moon. Heavy items like habitat building and lunar rovers can also be transferred.

Since payload, propellent and lander can arrive separately heavier items can be landed on the Moon from a spacestation than in a single launch.

The ideal orbit for the DSG during construction of a Moon Base is probably very different from the orbit of the ship yard for the Mars Transfer Vehicle. Fortunately the DSG's orbit can be changed or a second one built.

People could go on direct SLS/Orion flights to the DSG. Most cargo could be launched to LEO on commercial launch vehicles.

So your saying we should operate two stations then?

{snip}

More like 3 spacestations.
LEO gateway spacestation to load SEP and chemical tugs.
LLO spacestation to garage lunar lander.
EML-1/2 spacestation for loading and repair of Mars transfer vehicles.

I think the manned Mars trip is 20-30 years away.

I hadn't considered EO stations.  I prefer NASA not own ISS-2.  My opinion on EO stations is the best way to get commercial stations is to design NASA missions that sign long-term leases for research projects based on the stations.  This doesn't really work in conjunction with plans to transfer ISS funding to SLS/Orion/DSG.

In order to avoid failing into a deep depression, I try to avoid thinking about Mars missions that involve SLS.  The last timeline I stumbled across has Martian orbital missions beginning in the early 2040's.  If Congress actually cared about humans on Mars, they'd shovel a couple billion per year in SpaceX's direction and get out of the way.  Even without government funding, I expect SpaceX can still get to Mars far sooner than 2040.  As such, I think it is best to limit landers used in conjunction with SLS to plausible targets like NEOs or, pending what I learn in this conversation, the Lunar surface.

I suspect that the DSG, or replacement e.g. Bigelow/ULA depot, will end up in LLO.

For the Moon base a Bigelow B330-MDS module would mass 20-30 tonnes. That is payload to the transportation system since the mass of the lander and propellant are additional to that.
https://en.wikipedia.org/wiki/B330

If it were up to me I'd spend the $2.3B on the Bigelow/ULA offer, and build the SEP PPE module.  The PPE would be launched with a small multi-port module as close to LLO as a FH can get and let the PPE take care of the rest.  B330-ACES docks with the PPE and we have most of a station core, plus an ACES that can be reused.  Orion still won't be able to return without an upgrade or refueling, but at least we have useful hardware out there.

Offline ncb1397

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Re: SLS Lander?
« Reply #22 on: 02/24/2018 02:45 pm »

While this is an interesting thought exercise, I don't see how it gets us closer to the specifications a Lunar lander designed to work with SLS/Orion requires.

The solution is an upgraded Orion service module made in the United States. Bump the solar power capability to 20 kw from 11 kw to match NeMO, add Next-C or AEPS engines. Acting as a lunar lander, It could self ferry itself ahead of crew to whatever orbit Orion can reach(might even be considered LLO) with the upgraded service module utilizing the extra lift capability of the Block 1B. The descent modules get re-used on the surface for power, consumable storage, fuel storage. Once you get some sort of fuel production going on the surface, you could look at fueling them and sending them back up to orbit. Orion would just use ESMs until this is available, freeing up Europe to focus on other stuff (like a European lunar hab equivalent to their contribution to ISS).

Either that or base the lander at DSG like what seems to be the plan. The difference between 4.5 km/s and 5.5 km/s for a lander isn't exactly a deal breaker.

That isn't the current plan though.  NASA's RFI requested drop-in replacements for Shuttle OMS engines.  I guess the SM tanks could be stretched but that will cut into payload capacity.  How long would it take and how much would it cost before an upgraded Orion would be available?  How many more SLS launches are needed to send cargo?

https://www.nasaspaceflight.com/2018/02/nasa-releases-rfi-new-orion-service-module-engine/

Why are you adding a ~20% margin for LLO to surface and back compared to a minimum margin of ~9% for L2 halo orbits?


Why would a better service module cut into payload capacity? You would likely get more capability from the service module to maneuver co-manifested payloads than you would lose from the EUS. The numbers I give for landers are from the following white paper on page 4(Figure 3):

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20150019648.pdf

Their emails are on the paper if you would like to ask them directly.

Offline Jim

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Re: SLS Lander?
« Reply #23 on: 02/26/2018 12:24 pm »
  If Congress actually cared about humans on Mars, they'd shovel a couple billion per year in SpaceX's direction and get out of the way.

That is not how it works.  the congress never directly funds a company.

Offline Welsh Dragon

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Re: SLS Lander?
« Reply #24 on: 02/26/2018 02:05 pm »
  If Congress actually cared about humans on Mars, they'd shovel a couple billion per year in SpaceX's direction and get out of the way.

That is not how it works.  the congress never directly funds a company.
Except of course that it (bizarrely to a European) mandates specific rockets for specific missions, thereby ensuring the manufacturers of those rockets get funded.

Offline IRobot

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Re: SLS Lander?
« Reply #25 on: 02/26/2018 02:26 pm »
More like 3 spacestations.
LEO gateway spacestation to load SEP and chemical tugs.
LLO spacestation to garage lunar lander.
EML-1/2 spacestation for loading and repair of Mars transfer vehicles.

I think the manned Mars trip is 20-30 years away.
LLO does not seem necessary nor offer any significant advantage.

Offline speedevil

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Re: SLS Lander?
« Reply #26 on: 02/26/2018 05:26 pm »
LLO does not seem necessary nor offer any significant advantage.

It can, if you use it to avoid having to take your TEI fuel (and possibly rocket engine) down to the moon and back.

Offline Lar

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Re: SLS Lander?
« Reply #27 on: 02/26/2018 05:39 pm »
  If Congress actually cared about humans on Mars, they'd shovel a couple billion per year in SpaceX's direction and get out of the way.

That is not how it works.  the congress never directly funds a company.
Except of course that it (bizarrely to a European) mandates specific rockets for specific missions, thereby ensuring the manufacturers of those rockets get funded.
I think they mandate things that only a particular rocket (or company) has. This is pretty common in government generally here these days.
"I think it would be great to be born on Earth and to die on Mars. Just hopefully not at the point of impact." -Elon Musk
"We're a little bit like the dog who caught the bus" - Musk after CRS-8 S1 successfully landed on ASDS OCISLY

Offline spacenut

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Re: SLS Lander?
« Reply #28 on: 02/26/2018 06:09 pm »
Wouldn't ELM-1 or 2 be a better location for a station and design a lander to be refueled there?  Most companies and countries can reach these locations with existing rockets.

Offline A_M_Swallow

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Re: SLS Lander?
« Reply #29 on: 02/26/2018 07:46 pm »
LLO does not seem necessary nor offer any significant advantage.

It can, if you use it to avoid having to take your TEI fuel (and possibly rocket engine) down to the moon and back.

Space activities will always be mass limited. Colonisation will also be very money limited. Astrobotic Technology are currently charging $1,200,000 per kilogram to land a payload on the Moon. Even if larger landers get the price down to $100,000/kg transporting ten tonnes of fuel would cost

10,000 * $100,000 = $1,000,000,000

Bigelow claims it will sell you a spacestation for that billion dollars (placement extra).

Offline A_M_Swallow

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Re: SLS Lander?
« Reply #30 on: 02/26/2018 08:16 pm »
Wouldn't ELM-1 or 2 be a better location for a station and design a lander to be refueled there?  Most companies and countries can reach these locations with existing rockets.

Spacestation at EML-2 Vs. LLO Vs. both is definitely a trade off.

Lunar surface to Low Lunar Orbit (LLO) and back has a delta-v of 2 * 1.87 = 3.74 km/s
Lunar surface to Lagrangian point 2 (EML-2) and back has a delta-v of 2 * 2.52 = 5.04 km/s

A larger delta-v means the landers need much larger fuel tanks and possibly more engines for the same payload.

Various launch vehicles have different prices and deliver significantly different amounts of payload to LLO and EML-2.

Money, mass of payload to lunar surface and location of spacestation can be traded. Unlike Apollo this is a continuing operation so the trade can be over say 10 landings using the same spacestation.

Offline Coastal Ron

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Re: SLS Lander?
« Reply #31 on: 02/26/2018 08:35 pm »
  If Congress actually cared about humans on Mars, they'd shovel a couple billion per year in SpaceX's direction and get out of the way.

That is not how it works.  the congress never directly funds a company.

With earmarks they did (and those might be coming back), and the NASA Authorization Act of 2010 was specific enough in it's requirements that both Boeing and Lockheed Martin did not have to bid to "win" the new work - NASA used novation to swap out the Constellation contracts for the SLS and Orion MPCV contracts.

But to your point, when things are done correctly, Congress is not involved in the contract awards process.
If we don't continuously lower the cost to access space, how are we ever going to afford to expand humanity out into space?

Offline mike robel

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Re: SLS Lander?
« Reply #32 on: 02/26/2018 09:02 pm »
Even so, earmarks had to flow through a contract; I don't believe they ever when directly form Congress to a vendor...unless of course, they did.

Offline speedevil

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Re: SLS Lander?
« Reply #33 on: 02/26/2018 10:21 pm »
Space activities will always be mass limited. Colonisation will also be very money limited. Astrobotic Technology are currently charging $1,200,000 per kilogram to land a payload on the Moon. Even if larger landers get the price down to $100,000/kg transporting ten tonnes of fuel would cost

10,000 * $100,000 = $1,000,000,000

Bigelow claims it will sell you a spacestation for that billion dollars (placement extra).

Err...
If we're dragging other providers claims into it, SpaceX claims to be able to do it (eventually) for around $50/kg, not $100000/kg.
https://forum.nasaspaceflight.com/index.php?topic=41682.msg1731818#msg1731818
(Assuming numbers applicable to making passenger transport plausible, and detanking and retanking in LEO and LLO with another vehicle. )

Even more near-term launchers (including SLS) can probably comfortably beat $100000/kg.

Offline A_M_Swallow

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Re: SLS Lander?
« Reply #34 on: 02/26/2018 11:05 pm »

Err...
If we're dragging other providers claims into it, SpaceX claims to be able to do it (eventually) for around $50/kg, not $100000/kg.
https://forum.nasaspaceflight.com/index.php?topic=41682.msg1731818#msg1731818
(Assuming numbers applicable to making passenger transport plausible, and detanking and retanking in LEO and LLO with another vehicle. )

Even more near-term launchers (including SLS) can probably comfortably beat $100000/kg.

These figures are to the Moon's surface not to LEO.

" around $50/kg"
Which decade?

Offline speedevil

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Re: SLS Lander?
« Reply #35 on: 02/26/2018 11:19 pm »

Err...
If we're dragging other providers claims into it, SpaceX claims to be able to do it (eventually) for around $50/kg, not $100000/kg.
https://forum.nasaspaceflight.com/index.php?topic=41682.msg1731818#msg1731818
(Assuming numbers applicable to making passenger transport plausible, and detanking and retanking in LEO and LLO with another vehicle. )

Even more near-term launchers (including SLS) can probably comfortably beat $100000/kg.

These figures are to the Moon's surface not to LEO.

" around $50/kg"
Which decade?

Whenever you believe P2P level service is plausible.
Note that the BFS, refuelled in LEO can do 20 tons to the lunar surface and back, every three weeks, if it can do Mars at all.

SLS - well - something would need to be rescheduled to get something on the lunar surface before 2030.

Offline A_M_Swallow

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Re: SLS Lander?
« Reply #36 on: 02/27/2018 10:09 am »
Currently Falcon Heavy is $90M for 63,800 kg to LEO. That is $1,420/kg
Block 1B SLS is ~$1B for 105,000 kg to LEO. That is $9,524/kg

The LEO to lunar surface round trip is 2 * 5.93 = 11.86 km/s

According to its Wikipedia article the BFR propellant mass is 240,000 kg (530,000 lb) CH4 and 860,000 kg (1,900,000 lb) LOX.

So the fuel for the round trip using Falcons and upper stage BFR refuelled in space would cost at least
(240,000kg + 860,000kg) * $1420/kg = $1,562,000,000

For a 20 tonne payload that is $1,562,000,000 / 20,000kg = $78,100/kg

Offline speedevil

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Re: SLS Lander?
« Reply #37 on: 02/27/2018 11:42 am »
For a 20 tonne payload that is $1,562,000,000 / 20,000kg = $78,100/kg
No, it is not.
See this thread.
In short, 100% reusability slashes costs a lot. If it works, which is a more appropriate topic in other threads.

Re: SLS Lander?
« Reply #38 on: 02/27/2018 11:52 am »
For a 20 tonne payload that is $1,562,000,000 / 20,000kg = $78,100/kg
No, it is not.
See this thread.
In short, 100% reusability slashes costs a lot. If it works, which is a more appropriate topic in other threads.
Assuming it 100% doesn't work is factually wrong, as demonstrated by F9's refurbishment costs of less than half a new core since the 1st ever refurbishment. And that's discounting even a slow, pessimistic improvement in ref. costs overtime.

I understand that A_M_Swallow' post implies using FH to refuel the BFS (with a wrong price/kg quoted).
SpaceX plans to use the BFR for distributed lift, to leverage the economy afforded by fully reusable vehicles.

For his math to make sense, a single (fully reusable) launch of BFS tanker + BFR booster should cost 213 million $ for 150 tons of propellant to LEO. That's probably close to the fully expendable price (consider that SX currently charges 150M$ for a fully expendable FH, with 28 engines and 3 cores)
« Last Edit: 02/27/2018 11:56 am by AbuSimbel »
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Offline A_M_Swallow

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Re: SLS Lander?
« Reply #39 on: 02/27/2018 01:27 pm »
For a 20 tonne payload that is $1,562,000,000 / 20,000kg = $78,100/kg
No, it is not.
See this thread.
In short, 100% reusability slashes costs a lot. If it works, which is a more appropriate topic in other threads.

There are no prices on that thread so it does not support your case.

 

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