A Return to the Moon by the Apollo 11 50th Anniversary.

[RGClark]

Argues the SLS as early as 2017 can be used to launch manned lunar lander missions:

SLS for Return to the Moon by the 50th Anniversary of Apollo 11.
http://exoscientist.blogspot.com/2012/10/sls-for-return-to-moon-by-50th.html

The argument for why this is doable is rather simple. The Early Lunar Access(ELA) proposal of the early 90's, which deserves to be better known actually, suggested that by using a lightweight 2-man capsule and all cryogenic in-space stages that a manned lunar lander mission could be mounted with only 52 mT required to LEO, half that previously thought necessary.
The only technical complaint about its feasibility was that it required a crew capsule of only 3 mT empty weight. But the kicker is NASA is planning a [ame="http://en.wikipedia.org/wiki/Space_Exploration_Vehicle"]Space Exploration Vehicle(SEV)[/ame] at that same low 3 mT empty weight. So the SLS at a 70 mT payload capability will be able to launch such a mission using the SEV as crew capsule following the ELA architecture with plenty of margin.


Bob Clark

 

[Hlynkacg]

Honsest question.

Do you really think that the SLS will be ready for manned flights before 2017 if ever?

Likewise seeing as the individual SSMEs planned for use on the core stage cost as much as an entire Falcon9 launch is there really any reason to use the SLS at all?

For the same dollar amount you could have a multi-launch EOR or LOR mission profile based around five Falcon9s.

 

[kamaz]

Do you really think that the SLS will be ready for manned flights before 2017 if ever?

SLS itself? Yes. It will have no payloads, however...

Likewise seeing as the individual SSMEs planned for use on the core stage cost as much as an entire Falcon9 launch is there really any reason to use the SLS at all?

This question is mis-stated. NASA has 15 SSMEs left over from the Shuttle program. These are already paid for, hence their cost is zero. Since SLS Block I uses 4 of these, this stock is enough for 3 launches. (At the moment, only 2 Block I launches are planned).

SLS Block II (i.e. missions SLS-3 and later according to the current schedule) will used an expendable version of SSME, which is expected to be cheaper.

For the same dollar amount you could have a multi-launch EOR or LOR mission profile based around five Falcon9s.

2x F9 Heavy would be better. Less complicated planning.

 

[BruceJohnJennerLawso]

Honsest question.

Do you really think that the SLS will be ready for manned flights before 2017 if ever?

Likewise seeing as the individual SSMEs planned for use on the core stage cost as much as an entire Falcon9 launch is there really any reason to use the SLS at all?

For the same dollar amount you could have a multi-launch EOR or LOR mission profile based around five Falcon9s.

Good point. SLS may fly, as there may be some applications that demand a single launch for mission simplicity, fewer launches requiring less groundtrack cost, no orbital rendezvous requirement, and the ability to launch very large individual payloads. BUT, all of that being said, SLS probably wont see much use at all due to how much cheaper the Falcon Heavy will probably be. I have to admit, SLS probably is a bit of a stalling act by the Obama administration, but having a modern SHLV available for certain missions will have its uses, regardless of its expenses.

 

[Urwumpe]

I have to admit, SLS probably is a bit of a stalling act by the Obama administration, but having a modern SHLV available for certain missions will have its uses, regardless of its expenses.

Thats a fallacy. If you look at the world around you, you might notice, that only few ships are left, which are not based on transporting standard size containers. It is not about a "regardless of its expenses". You only use special ships for special payloads, that can't fit into containers for that price. Eg oil. Or cars, or living animals.

Also, the ground costs for launchers are mostly fixed costs, regardless how often you launch. A small medium size launcher that launches 12 times per year, is MUCH cheaper in terms of ground infrastructure, than a HLV that launchers only once per year.

 

[BruceJohnJennerLawso]

Thats a fallacy. If you look at the world around you, you might notice, that only few ships are left, which are not based on transporting standard size containers. It is not about a "regardless of its expenses". You only use special ships for special payloads, that can't fit into containers for that price. Eg oil. Or cars, or living animals.

Also, the ground costs for launchers are mostly fixed costs, regardless how often you launch. A small medium size launcher that launches 12 times per year, is MUCH cheaper in terms of ground infrastructure, than a HLV that launchers only once per year.

Yes, I am more of a medium launcher thinker, but there are a few places where building HLVs is better than multilaunch:

-lower risk due to fewer launches & less operational complexity: the apollo-SaturnV combination worked well because it required tracking effectively only one vehicle up to LOI. This is easier on groundtrack costs & on the teams needing to do that tracking on the ground
-If the missions window is short, multiple launches could keep the mission well behind schedule due to the various reasons for launch holds: weather, other spacecraft (MSL was delayed to avoid hitting the ISS with debris), technical failures, etc
-Not every payload is going to fit into the "shipping container" analogy.
-HLVs are much more publicity friendly. Yes I know most of us could care less what the media says about space exploration, but one very shiny SLS launch would be a much more useful PR event than 12 Atlas V launches. Voters expect NASA to show the results, and a big launch would be the chance to show off. Just the way it is I guess :shrug:
-Particular types of payloads: If you were launching a NERVA, would you want to launch it on a medium launcher or a Saturn V? Even if the payload is well under that launchers max-to-orbit, mission planners like that guarantee that theres an extra margin of error (more available burn time) that prevents a very messy reentry & subsequent disaster.

Thats pretty much all Ive got, but I have thought recently that NASAs biggest problem was that they never created their "Soyuz"- a highly reliable, low cost, disposeable vehicle that they could build almost regardless of budget cuts. Hopefully Falcon 9 can become that for NASA in the future

 

[Urwumpe]

-HLVs are much more publicity friendly. Yes I know most of us could care less what the media says about space exploration, but one very shiny SLS launch would be a much more useful PR event than 12 Atlas V launches. Voters expect NASA to show the results, and a big launch would be the chance to show off. Just the way it is I guess :shrug:

Not really. People actually don't want to think about it, and when a commercial company can haul way more stuff into orbit in a much shorter time for much less of the money, even the biggest rocket on Earth will only ONCE bring you positive PR. Results count.

The rest is a bit hypothetical: Can't we do orbital assembly? if not, why are we still unable to produce things in space as good or better as on Earth? Why must a big payload and rocket be assembled on earth?

 

[BruceJohnJennerLawso]

Not really. People actually don't want to think about it, and when a commercial company can haul way more stuff into orbit in a much shorter time for much less of the money, even the biggest rocket on Earth will only ONCE bring you positive PR. Results count.

The rest is a bit hypothetical: Can't we do orbital assembly? if not, why are we still unable to produce things in space as good or better as on Earth? Why must a big payload and rocket be assembled on earth?

well..... :shrug:.

I was just providing the list of possible reasons, but I can still think of a lot more against building an HLV. I have been hoping to bring that last point up though:

What is wrong with on-orbit assembly?!?

Robert Zubrin claims that an HLV is needed for mars direct, but why? Ive never heard a clear reason why building spacecraft module by module in orbit is an inherently flawed process. For that matter it makes more sense to carry over all of the modular assembly techniques learned from the ISS to future missions, given that many engineers, controllers, & crew have done it multiple times before.

 

[Urwumpe]

Robert Zubrin claims that an HLV is needed for mars direct, but why? Ive never heard a clear reason why building spacecraft module by module in orbit is an inherently flawed process. For that matter it makes more sense to carry over all of the modular assembly techniques learned from the ISS to future missions, given that many engineers, controllers, & crew have done it multiple times before.

When Mars Direct was developed, on-orbit assembly like done on the ISS was still science fiction. Nobody really knew how it will work out about ten years later.

 

[T.Neo]

What is wrong with on-orbit assembly?!?

It enables a BEO human spaceflight program to be executed without the creation of a billions-of-dollars HLV development program or the requirement to sustain specific workforces and infrastructure.

 

[BruceJohnJennerLawso]

It enables a BEO human spaceflight program to be executed without the creation of a billions-of-dollars HLV development program or the requirement to sustain specific workforces and infrastructure.

Reads once :huh:
Reads twice Ohhhh I get it now...

 

[kamaz]

What is wrong with on-orbit assembly?!?

It's not assembly, it's propellant.

Trans-Mars Injection from Low Earth Orbit requires delta-v of 4.3 km/s. If your kick stage uses LH2/LOX (4.5km/s exit velocity), then it corresponds to mass ratio of about 2 -- i.e., you need 1kg of propellant per 1kg of payload (neglecting mass of engines and tankage).

Problem is, LH2 is not storable; it boils off. So, your kick stage must be fired as soon as possible after getting into orbit. And, since you need the kick stage with mass equal to that of the payload, then the best thing you can do is two launches: payload first, then the kick stage. Within one orbit after the two parts dock together, you do your injection burn, to avoid propellant losses due to LH2 boiloff.

At this point, you realize that it makes more sense to split your 100t payload into two 50t chunks, each coupled with a 50t kick stage. The number of launches is the same, but you avoid docking.

Your idea would make sense, if you had a low-mass, high-Isp drive (like VASIMR is hyped to be). Then, indeed, you could assemble the spacecraft in LEO (say, out of 10 parts), then do a single launch to lift the kick stage.

 

[Urwumpe]

You could also store LH2 in space, actually even better than on Earth, since space is REALLY cold if are in a shadow. Compressors and cooling systems would be still mandatory... but not the massive plumbing needed on Earth.

 

[T.Neo]

LH2 boiloff rate depends on the technology and system in question. Obviously for in-space assembly or an orbital propellant depot, you want the lowest boiloff rates that are possible and practical.

A propellant depot is regarded as a very enabling technology, because splitting up propellant from other components allows you to fit various components on smaller launchers (the Apollo spacecraft stack of CSM/LM/S-IVb, for example, was quite light without propellant) and also create a market for launching propellant.

 

[RGClark]

Exploration Alternatives: From Propellant Depots to Commercial Lunar Base.
November 15th, 2012 by Chris Bergin

NASA managers have since created an option for a return, listed as a Lunar Surface Sortie (LSS) mission via the Exploration Systems Development Division (ESD) Concept Of Operations (Con Ops) document (L2), allowing it to become a Design Reference Mission (DRM) alternative, potentially at the expense of a NEA mission in the early to mid 2020s.
While this option remains on the cards, source information acquired by L2 this week revealed plans for a “game-changing” announcement as early as December that a new commercial space company intends to send commercial astronauts to the moon by 2020.
According to the information, the effort is led by a group of high profile individuals from the aerospace industry and backed by some big money and foreign investors. The company intends to use “existing or soon to be existing launch vehicles, spacecraft, upper stages, and technologies” to start their commercial manned lunar campaign.
The details point to the specific use of US vehicles, with a basic architecture to utilize multiple launches to assemble spacecraft in Low Earth Orbit (LEO). The details make direct reference to the potential use of propellant depots and fuel transfer technology.
Additional notes include a plan to park elements in lunar orbit, staging a small lunar lander that would transport two commercial astronauts to the surface for short stays.
http://www.nasaspaceflight.com/2012...ives-propellant-depots-commercial-lunar-base/

I first thought the commercial plan was going to follow the Early Lunar Access (ELA) proposal because it mentioned landing two commercial passengers on the Moon. ELA was a lightweight architecture that used a small two-man capsule:

Encyclopedia Astronautica.
Early Lunar Access.
http://www.astronautix.com/craft/earccess.htm

But it is unlikely in the commercial plan they mean the passengers are to fly alone without one or more professional pilots. And also the article mentions the commercial plan is to use on orbit assembly. But by using the Falcon Heavy or the SLS you could launch the ELA architecture with a single launch.

Still, using two launches of the Delta IV Heavy both at its maximum payload to orbit of 25 mT we could launch the ELA architecture. Even if the Delta IV Heavy is not man rated, we could use separate launchers to take the astronauts to orbit and transfer them to the Moon vehicle after it is assembled.

For the NASA proposal, the article mentions the Lunar Surface Sortie (LSS) proposal. But this was still to use a 4 man capsule, which likely means the large, heavy Orion. It also would involve a separate lunar crew module, also at variance with the lightweight ELA architecture.

This lunar lander of the LSS proposal would then likely be akin to the large, expensive Altair lunar lander. So this proposal would be similar to the Constellation program whose high expense caused it to be cancelled. Better would be if NASA went small following the ELA architecture to use a single, small capsule that would carry the astronauts all the way from LEO to the lunar surface and back again. This would allow a NASA return to the Moon with a proportionally small additional cost above that of the SLS itself.


Bob Clark

 

[Urwumpe]

It would be more interesting, if the ELA architecture could be launched on any launcher capable of hauling 25-30 tons of payload. Then you would not need to be depending on a single LV, but could choose the best offer for your launch.

Still, ELA is not the best architecture for repeated flights. It is great for getting to the moon with minimal changes to the ground infrastructure (on Earth). But it is not the optimal for repeated flights. There the TTM24 architecture (also developed by NASA) gets more interesting, despite being nuclear.

 

[T.Neo]

What about a non-nuclear version of the TTM24 architecture?

 

[Urwumpe]

What about a non-nuclear version of the TTM24 architecture?

Would be pretty hard to reuse the transfer stage then. Aerobraking could be one improvement there, but it would require a heat shield then.

There is a NASA concept from the 80s about chemical stages to be used for such missions, but all had been pretty complex, like transporting fuel modules in the shuttle payload bay.

A big dump propellant tank launcher might be a good choice there, but you then still need small "oilers" or space tugs to get the fuel transported where you need it.

Important is, that you have limited defined roles for the spacecraft, to define the requirements on them. Not necessarily spacecraft designs. But you need one working mission architecture to permit spacecraft to be integrated. For example a Boeing transfer stage with a SpaceX capsule.

Same with propellant depots. Ideally it is just a concept that can be filled by any actual design. But you still need to get its interfaces to the other entities in your mission architecture defined.

Fixed interfaces, variable solutions, that is what gives you the freedom to use commercial operations. The alternative would be a military style spaceflight, as we know.

 

[RGClark]

Just saw this article by legendary Apollo manager Chris Kraft mentioned on the NasaSpaceFlight.com forum:

Space Launch System is a threat to JSC, Texas jobs
By Chris Kraft and Tom Moser | April 20, 2012 | Updated: April 20, 2012 8:20pm

We are wasting billions of dollars per year on SLS. There are cheaper and nearer term approaches for human space exploration that use existing launch vehicles. A multicenter NASA team has completed a study on how we can return humans to the surface of the moon in the next decade with existing launch vehicles and within the existing budget. This NASA plan, which NASA leadership is trying to hide, would save JSC and create thousands of jobs in Texas.
http://www.chron.com/opinion/outloo...tem-is-a-threat-to-JSC-Texas-jobs-3498836.php

Since Kraft is opposed to the SLS and he says this plan uses existing launch vehicles, it can't use the SLS or the Falcon Heavy. It must then use something similar to the Early Lunar Access plan that uses orbital assembly, perhaps using two launches of the Delta IV Heavy.
Like the suppressed report that suggested orbiting propellant depots could accomplish the goals of the SLS at lower cost, this report will eventually also come out. So who's got the inside scoop?


Bob Clark

 

[RGClark]

This article by Amy Shira Teitel about the Chris Kraft piece discusses and links to a NASA report showing propellant depots can allow BEO missions without the SLS, saving billions:

EX-FLIGHT DIRECTOR URGES NASA TO KILL NEXT ROCKET SYSTEM.
Analysis by Amy Shira Teitel
Wed Apr 25, 2012 01:00 PM ET
http://news.discovery.com/space/mercury-flight-director-urges-nasa-to-kill-sls-120425.html

So this is probably the report referred to by Chris Kraft:

"Propellant Depot Requirements Study Status Report"
http://images.spaceref.com/news/2011/21.jul2011.vxs.pdf

The report discusses several scenarios for lunar, asteroidal, or Mars missions without using heavy lift vehicles by using propellant depots. It does discuss use of the Falcon Heavy in some scenarios, but others use the Delta IV Heavy. About this last, it's interesting they give the max payload of the Delta IV Heavy as 28 mT. But the highest I ever read it having was 25 mT. Anyone know what modifications to the Delta IV Heavy would allow it to have this high a payload capability?
A disadvantage of the approaches discussed however is the large number of launches required even for the lunar missions, 6 for the Falcon Heavy and 10 for the Delta IV Heavy. This is because the scenarios use the large, heavy Orion capsule, the service module, and a separate, large lunar lander, likely akin to the Altair lunar lander.
On the other hand if instead the Early Lunar Access (ELA) architecture were used it could be done with a single launch of the Falcon Heavy or two with the Delta IV Heavy:

Encyclopedia Astronautica.
Early Lunar Access.
http://www.astronautix.com/craft/earccess.htm


Bob Clark