Budget Moon Flights: Ariane 5 as SLS upper stage, page 2.

Copyright 2013 Robert Clark

Artist's rendering of the Space Launch System Block 1 sitting on Launch Pad 39B with the Orion spacecraft at sunrise.

 In the blog post Budget Moon Flights: Ariane 5 as SLS upper stage, I noted that using an Ariane 5 core stage would be a quick and low cost means of getting a higher payload capacity than the 70 mT NASA was giving for the 2017 SLS first launch. This would make it much easier to conduct a manned lunar lander mission using the SLS. However, finally, NASA has acknowledged that the Block 1, first version of the SLS to launch in 2017 will have a 90+ mT payload capacity not the 70 mT always stated by NASA:

SLS Dual Use Upper Stage (DUUS).
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20130013953_2013013757.pdf

 This is important since it means we will have the capability to do manned lunar landing missions by the 2017 first launch of the SLS:

SLS for Return to the Moon by the 50th Anniversary of Apollo 11, page 5: A 90+ metric ton first launch of the SLS.
http://exoscientist.blogspot.com/2013/09/sls-for-return-to-moon-by-50th.html

  Still, because of the even higher payload possible using an upper stage, NASA might still want to consider getting a quick and low cost upper stage by using the Ariane 5 core. In that "SLS Dual Use Upper Stage (DUUS)" report are given some specifications for the DUUS. They state they want a highly weight optimized stage, which the Ariane 5 core would certainly fulfill. The Vulcain engine though has thrust size about twice that of the specified 100 - 120K lb range, and the 170 mT of propellant is also larger than the specified 130 mT propellant load. However, these are so much superior to the specified requirements it should result in significantly greater payload delivery than the stated 130 mT to LEO, perhaps to the 150 mT range.
 However, a problem is the 18.3 m specified max height. The Ariane 5 core is at 30.5 m height. Likely the height limitation is coming from limitations on the size and height of the facilities during stage integration. I'll find out if that is a firm limit.
 We could cut down the size of the Ariane 5 core to make it 130 mT in propellant load. Proportionally this would bring the height down to about 20 m, closer to the max. height. It turns out that shortening a stage is rather easy technically so this should still be doable by the 2017 first launch of the SLS.
 Another possibility would be to use the same propellant tank tooling for this DUUS stage as that used by NASA to make the 8 meter wide SLS tank, while using the other components such as the engine of the Ariane 5. However, the idea is to get a low cost upper stage in a short time frame. This might be a costly modification that might also be difficult to manage by the 2017 SLS first launch.
 This possibly though could open up an additional means of lightweighting the stage. We could use aluminum-lithium alloy instead of the standard aluminum used for the Ariane 5. NASA is also planning to use standard aluminum for the SLS core. But as I discuss in SLS for Return to the Moon by the 50th Anniversary of Apollo 11, page 4: further on lightweighting the SLS core, new versions of Al-Li have been developed that could be used for this purpose.
 However, due to the natural inertia of large agencies it might be difficult to change the decision and go with Al-Li for the SLS core. But this decision might be easier to make in regards to the smaller upper stage which wouldn't need as much of the more expensive Al-Li and for which getting a lightweight stage is a much greater priority.

  Bob Clark

SLS for Return to the Moon by the 50th Anniversary of Apollo 11, page 5: A 90+ metric ton first launch of the SLS.

Copyright 2013 Robert Clark

 Finally someone at NASA acknowledges that the Block 1, first version of the SLS to launch in 2017 will have a 90+ mT payload capacity not the 70 mT always cited by NASA:

SLS Dual Use Upper Stage (DUUS).
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20130013953_2013013757.pdf

 This is important since it means we will have the capability to do manned lunar landing missions by the 2017 first launch of the SLS.

 As discussed in the blog post SLS for Return to the Moon by the 50th Anniversary of Apollo 11, page 2: Orion + SEV design, a 90+ metric ton launcher means we can even use the Orion as the crew capsule. This is important for political reasons since the great expense spent on it means there would be a great desire among its supporters to see it be used. 

 There also is a preference at NASA for the departure stages from the lunar surface and from lunar orbit to use hypergolics, which have the surety of igniting on contact. Then another advantage of a 90+ mT SLS is that the heavier hypergolics can be used for these stages rather than the lightweight hydrogen-fueled stages I suggested in that blog post. In an upcoming post I'll show using existing hypergolic stages how we can get a lunar landing mission at less than 90 mT to LEO.

  For any of these methods it is important to use currently existing stages rather than developing them from scratch. A big reason that NASA ruled out a return to the Moon was because of the assumption that it required the development of new Altair-sized lander at a $10 billion development cost. But the need for a 45 mT Altair-sized lander is provably false as shown by the Apollo lander at one-third the size. And simply adapting already existing stages reduces the cost to a fraction of that needed for an Altair.

 So NASA is making expensive policy decisions such that we can't return to the Moon based on provably wrong assumptions. One is that the Block 1 would only have a 70 mT payload capability and so would require an expensive upper stage to increase the payload to do lunar missions, and another is that a lunar lander would require an additional $10 billion development.

 In fact, once you recognize the, obvious, fact that a lunar mission does not require an Altair-sized lander then so many possibilities become apparent. We did not have the great variety of existing launchers back in the Apollo days that we have now. If you allow your lander to be at or smaller than the Apollo lander then there are a variety of launchers that could be used for lunar missions, not just the SLS. And since they are already existing, or will be soon such as the Falcon Heavy, there would be no huge, multi-billion dollar development cost to use them. 

 So likewise also is the case for the in-space stages needed. They are already currently existing and would require relatively minor adaptations to be used for a lunar lander, for example.

 Indeed we could do manned lunar missions for what NASA is currently paying the Russians to send a crew of 3 to the ISS. The implications of that are jarring: we could have regular manned flights to the Moon for the same amount as what we are currently paying to send regular manned flights to the ISS.  And since the cargo flights to the Moon would be similarly low cost and using Bigelow style lightweight habs would allow a habitation module to be sent to the Moon on a single flight, we could have a manned lunar base for the same amount as what we are paying to sustain the ISS.

 All this comes from simply the mental reset that a lunar mission does not require the $10 billion Altair.

 Free your mind, the rest will follow.

    Bob Clark

Note: thanks to M. Moleman for discussing the NASA report "SLS Dual Use Upper Stage (DUUS)" on his blog.

Budget Moon Flights: Ariane 5 as SLS upper stage.

Copyright 2013 Robert Clark

Delta IV Heavy Orion Circumlunar Test Flight.

I’m fairly sure looking at the capabilities of the Delta IV Heavy with the upgraded RS-68a engine, about 28 metric tons to LEO, that it could launch the Orion on that 2014 test launch on an actual circumlunar flight, not just to 3,600 miles out as currently planned. A circumlunar flight would result in a much more capable test of the Orion.

The Orion test is planned to only carry a dummy service module, so that will be much lighter. The flight is planned though to carry the launch abort system (LAS) so that detracts from the weight that can be launched.

Without the LAS the DIVH could definitely send the Orion on a circumlunar flight. With the LAS, it makes it a little more difficult to estimate since it is jettisoned before reaching orbit.

This makes the use of the SLS for that unmanned circumlunar test flight in 2017 even more dubious, since the DIVH could do that, even if removing the LAS is required. That is another reason why I argue NASA should be aiming for an actual unmanned lunar landing test with that 2017 SLS flight.

Low Cost Lunar Lander and Crew Module.
ULA has done studies on adapting the Centaur upper stage as a lunar lander stage so you would not need a huge, and hugely expensive, Altair lander. We already even have a crew module that could be used for such a lander in NASA’s SEV, which can be ready by 2017 for test flights:

Inside NASA’s New Spaceship for Asteroid Missions | Space.com.
by Clara Moskowitz, SPACE.com Assistant Managing Editor
Date: 12 November 2012 Time: 02:30 PM ET

If the current schedule holds, NASA could test-drive a version of the SEV at the International Space Station in 2017. http://www.space.com/18443-nasa-asteroid-spacecraft-sev.html

Ariane 5 Core as SLS Upper Stage.
NASA is considering a version of the upper stage to be used with the Block II version of the SLS that uses RL-10 engines instead of the J-2X:

SLS prepares for PDR – Evolution eyes Dual-Use Upper Stage.
June 1, 2013 by Chris Bergin
http://www.nasaspaceflight.com/2013/06/sls-pdr-evolved-rocket-dual-upper-stage/

This is expected to save on costs.

NASA also wants to encourage European participation in the proposed asteroid retrieval mission:

NASA Pitches Asteroid Capture To International Partners.
By Frank Morring, Jr.
Source: Aerospace Daily & Defense Report
June 28, 2013
http://www.aviationweek.com/Article.aspx?id=/article-xml/asd_06_28_2013_p01-01-592208.xml

Then a way to save further on development costs and to get European involvement would be to use the Ariane 5 core as the upper stage. It’s of common-bulkhead design to save mass. I recently learned it also uses the pressure-stabilized, “balloon tank”, method a la the Centaur to further save on tank mass.

The ESA also believes its Vulcain II engine can be made air-startable since this was planned for the Liberty rocket. The Vulcain uses a rather short nozzle since it is meant for ground launch, giving it a 432 s Isp. But simply giving it a nozzle extension would give it the ca. 462 s ISP of the RL-10.

Another key advantage is that because little additional development would be needed it might even be ready by the 2017 first launch of the SLS. Then this first 2017 launch of what was only to be a 70 mT interim version could have the 100+ mT capability of the later versions of the SLS. Such a version would clearly have the capability to do manned lunar lander missions.

You could also give this stage the RL-10 engines, instead of the Vulcain. The Vulcain weighs about 1,800 kg. Four RL-10′s would weigh 1,200 kg. So this would save 600 kg off the stage dry mass.

The NasaSpaceFlight.com article mentions the advantage of having different diameters for the hydrogen and oxygen tanks to maintain commonality with tooling of existing stages, and that is the reason for not having both tanks the same diameter. That would not be a problem of course with using the Ariane 5 core at a common 5.4 meter diamter. And someone noted on the Nasaspaceflight forum thread on this topic that for a uniform 8.4 m diameter, NASA could just use the same tooling for both that is used for the 8.4 meter SLS core stage tank.

For any of these possibilities it would be very good if NASA could use the composite tanks Boeing is investigating. Aerospace engineer Jon Goff on his blog noted ULA estimated their ACES proposed upgrade of the Centaur could get a 20 to 1 mass ratio by switching to aluminum-lithium for the tanks. And according to Boeing, an additional 40% can be saved off the Al-Li tank mass by using composites, resulting in an even larger mass ratio than 20 to 1:


NASA Sees Potential In Composite Cryotank.
By Frank Morring, Jr. morring@aviationweek.com
Source: AWIN First
July 01, 2013
http://www.aviationweek.com/Article.aspx?id=/article-xml/awx_07_01_2013_p0-592975.xml


Scaling up your stage mass, such as to the DUUS size, is also known to be able to improve your mass ratio. Imagine then all these mass ratio improving factors being applied. How high could the mass ratio get, perhaps to the 25 to 1, or even 30 to 1 range???

Imagine what you could do with a hydrolox stage with an ISP as high as ca. 462 s with a mass ratio as high as 30 to 1. (*)

Bob Clark


(*) By rocket equation, the delta-v is:  462*9.81ln(30) = 15,400 m/s.


Update, Sept. 28, 2013:

 Finally, NASA has acknowledged that the Block 1, first version of the SLS to launch in 2017 will have a 90+ mT payload capacity not the 70 mT always stated by NASA:

SLS Dual Use Upper Stage (DUUS).
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20130013953_2013013757.pdf

 This is important since it means we will have the capability to do manned lunar landing missions by the 2017 first launch of the SLS:

SLS for Return to the Moon by the 50th Anniversary of Apollo 11, page 5: A 90+ metric ton first launch of the SLS.
http://exoscientist.blogspot.com/2013/09/sls-for-return-to-moon-by-50th.html