The SLS: A layman’s view

SLS
The changing face of the SLS – will the rocket be as flexible as the 3D rendering? [IMG: NASA]
The Space Launch System. The World’s most powerful rocket, getting ready to blast humanity into deep space and on our long awaited journey to Mars (or should I say #JourneyToMarsTM). Star of so many CGI animations and NASA presentations that I’ve lost count. 

You’ve changed a bit since we first met – you used to look a lot more like the Saturn V, now you’ve shed the paint job and you look a lot more like a bunch of stuff from the Shuttle, but more of that later. See, the thing is I really, really want to see humanity go further into space and take a journey to Mars. I want to see a lander burrow under the ice and swim in the oceans of Europa, I want an incredibly advanced laboratory swooping through the plumes of Enceladus, I want a sub cruising the methane oceans of Titan – I guess I just want us to go places and do things. But SLS? I have my doubts.


Now, before I go any further I think a bit of disclosure is required as it will give a bit of context to what follows. I’m pretty obsessed by space travel – if you’ve looked at any of my other posts I’m sure you’ve worked that out, but it’s probably more important to say what I’m not. I’m not an engineer, I can’t quote you the specific impulse of a propulsion system or calculate the delta-V required to perform even the simplest of orbital adjustments, but I try to understand the basics  (I even watched a full MIT Aeronautical Systems engineering course and learnt a lot – I really recommend it!). I’m not an astrophysicist or a planetary scientist, but I try and hang in there and understand as much about these as I can as I find the subjects genuinely fascinating. I’m not a politician (thankfully) trying to balance the conflicting needs of my constituents, my party and my nation. Finally….I’m not American, although I spend a huge amount of time following and writing about the space activities of the United States.

So, with all of that said I suppose I could summarise by saying I’m coming at this as a layperson who just happens to have a massive interest in space and tries to keep up with developments as best I can. My main reason for writing this is that it’s the best way I know to put the pieces together and help me understand the situation and hopefully do the same for others.

One of the reasons I think it’s important to state that I’m not American is that I recognise I don’t have a full understanding of the US political system and it’s various players. Again, I try to keep up and count myself as reasonably well informed, but sometimes it can all seem a bit confusing. What I do have is a huge admiration for NASA. This is the organisation who put men on the Moon, who sent the Vikings to Mars giving me some of my earliest space memories and served up a succession of amazing planetary encounters via Voyagers 1 & 2. NASA built the Shuttle and employed the astronauts – as a kid they represented everything that was cool about science and technology to me. I think I used to fall into the common misconception of seeing NASA as one huge monolithic organisation, forgetting it started as a loose affiliation of centres spread around the US with different specialities and cultures and retains many of those characteristics to this day.

With all of that out the way, back to the matter at hand. I want to see a vibrant and effective NASA, pushing the boundaries of aeronautical and astronautical technology. I want them to be working on the key technologies needed to make us a truly spacefaring species with an ever growing understanding of the nature of our solar system and the galaxy beyond. Unfortunately it’s hard to ignore that NASA operates at the whims of politicians, sometimes seeming like equal parts punchbag and scapegoat. Even at the moment of the Agency’s biggest triumph, the first Moon landings, plans were already underway to slash NASA’s funding. It was a close run thing under Nixon as to whether the US would even retain a human spaceflight programme.

NASA ended up with the Shuttle – the lone survivor of former Administrator Thomas O. Paine’s grand post Apollo plans. Instead of being a space truck, a logistics vehicle for dragging people and cargo those tricky first hundred-plus miles out of Earth’s considerable gravity well to a series of orbital stations, the Shuttle now became all things to all people. As THE national launch system it had to balance the needs of the Department of Defence, the commercial satellite market and NASA’s planetary explorations as well as remaining the only means to construct a new space station when funding became available. The Shuttle had to do all of this and more and do it on reduced budgets, meaning before it ever flew the compromises had taken their toll and the aim of frequent, reliable aircraft-like operations could never be met.

All too soon, rocked by the Challenger disaster in 1986, America was looking for alternative launch vehicles and NASA began a search for a Shuttle replacement. There was the National Aerospaceplane (NASP), the DC-XA, the X-33 all chasing the promise of SSTO space access. As I mentioned earlier, I’m no engineer but I do understand enough about the rocket equation and mass fraction to know how elusive a practical SSTO will be. But in amongst these reusable replacements was the National Launch System (NLS).

comp
The (not so) changing face of heavy launch – L to R: The NLS, Ares V and the SLS

Following on from an earlier Air Force programme, the Advanced Launch System (ALS), the NLS would help power George H. Bush’s Space Exploration Initiative to the Moon and Mars and was based on Shuttle technology using 4 simplified expendable versions of the Shuttle’s RS-25 main engine mated to a core tank based on the Shuttle’s External Tank. Additional thrust would be supplied by solid rocket boosters (SRBs) similar to those already in use on the Shuttle. The NLS didn’t survive the transition into the Clinton era, but the DNA for future projects was laid down – a huge booster to take up where the Shuttle left off and use much of the same technology and – therefore – provide job security for the same workforce and a steady revenue stream for the same contractors.

This underlying concept returned under George W. Bush through the Constellation Program, the largest element of which was the heavy lift Ares V booster. Rather than the RS-25, Ares V would have used  5 less powerful and less complex RS-68s, again complimented by a pair of 5-segment SRBs (however, as the project wore on technical problems suggested that a move back to RS-25 engines might be needed). By the time Bush left office, the Constellation Program was behind schedule, over budget and facing many problems.

Following the report of the Augustine Committee, President Obama decided to cancel Constellation branding it “over budget, behind schedule, and lacking in innovation”. The new President hoped to move NASA towards looking at newer technologies that could help future explorations, but Congress had other ideas, and so the SLS was born in 2010 against the objections of the President.

Now, superficially at least, the idea of a large Saturn class booster capable of launching large planetary probes or human missions beyond LEO sounds OK. The problem is that the whole programme seems to be driven by the wrong motivations. Many call the SLS a ‘rocket without a mission’ pointing to the fact that, although the system could potentially do a lot of things, there are currently few firm plans beyond initial circumlunar tests and the ever nebulous asteroid retrieval mission – another hangover from the Constellation days. So while NASA talks bravely of its #JourneyToMars, the reality is that the component technologies needed for such a mission are in many cases currently no more than plans with decades of development, and billions of dollars in funding, required to bring them to fruition.

Under Congressional guidance, NASA is pursuing a ‘rocket first’ policy – build the booster that can fly the missions, then work on the missions at a later date. To this end we see Congress consistently exceeding NASA’s requests for SLS, which would seem a bonus were it not for the fact that this additional money comes from other NASA programmes including the development of the very technologies required to land on Mars. The only realistic outcome of this policy can be the extension of the time it will take to actually fly a crewed Martian mission, meaning that while SLS is still slated to fly an initial test mission in 2018 but the Mars landing wouldn’t happen until the mid 2030’s at the earliest. In the meantime a sporadic series flights would take place, although exactly what these would be is yet to be confirmed beyond basic outlines. Currently this equates to 5 flights of the SLS by 2026 including a human lunar orbital mission in 7 years time.

Throughout this incredibly low flight rate, NASA will be required to maintain all of the competencies required to build, service and operate the rockets and support a supply chain operating at such low volumes that it’s difficult to point to an equivalent. What we do know from the experience of the Shuttle is that it was difficult to maintain competencies and a supply chain with launch rates below around 4 flights a year. Given the Shuttle-derived nature of many of the SLS’s component parts it’s hard to see what will have changed here.

Then we have the matter of the engines. Each SLS core stage will use 4 RS-25 engines repurposed from the Shuttle programme. Currently, 16 of these are available – enough for 4 SLS flights assuming none are lost during testing or required as non-flight articles. In late 2015 NASA confirmed that Aerojet Rocketdyne had received a $1.16 billion contract to produce another 6 engines. The RS-25 had an extremely challenging development given that it needed to be reusable over many Shuttle flights. The engine ended up having a good reliability record across its Shuttle career, but now these reusable engines are recategorised as expendable. The new RS-25s will be built to an ‘expendable’ specification. And this brings me on to the real ‘elephant in the room’ when it comes to discussing the SLS – reusability.

The mantra increasingly heard from NASA is that reusability doesn’t work – the Shuttle proved that. Putting aside for a moment the fact that NASA tried from 1985 to 2000 to create a reusable replacement even after the Shuttle’s deficiencies were plainly apparent, these statements are thrown into far sharper relief by the activities of SpaceX and Blue Origin. Both companies have launched and recovered rockets from flights to space. In Blue Origin’s case these flights were sub-orbital, but the same vehicle has now been reflow three times with minimal refurbishment. SpaceX, on the other hand, are still to demonstrate reuse (although this will surely be attempted by summer 2016) but they have recovered two Falcon 9 first stage boosters from operational flights to LEO. If SpaceX and Blue Origin can continue to successfully develop recovery and reuse and, more importantly, demonstrate the financial benefits of their systems to potential customers, NASA’s rejection of reusability will become increasingly untenable.

FH
SpaceX Falcon Heavy, due for it’s initial launch late 2016 [IMG: SpaceX]
SpaceX are currently slated to fly the first demonstration of their Falcon Heavy rocket before the end of 2016 and while this doesn’t have the same predicted payload capacity as the SLS it will feature reusable cores. Falcon Heavy also benefits from the commonality of construction and components across the Falcon range, meaning SpaceX can actually benefit from economies of scale in a way SLS will never be able to.

The huge irony of this is that the only piece of SLS that has a demonstrated history of reusability, the RS-25 engine, will now be thrown away with each flight. Given that ULA are now developing a recovery system for the engine section of their proposed Vulcan booster, this seems incredibly profligate on NASA’s behalf, but maybe economy isn’t a big consideration in all of this.

The thing SLS can do far more effectively than any of its newer rivals is maintain the aerospace status quo, in place since Apollo. In the sixties it was essential for NASA Administrator James Webb to garner the widest base of congressional support possible to ensure NASA could deliver on Kennedy’s end of decade deadline for putting a man on the Moon. One way of doing this was to ensure the huge sums of money invested in Project Apollo were distributed to key congressional districts around the United States. A programme that employs many people right across the country would be far more difficult to kill than one that could be seen to be benefitting only one region, so the logic went.

This system prevails to the present day with Congressional representatives for those areas who benefit most from the long, drawn-out and costly SLS programme having the loudest voices and greatest influence on the distribution of NASA’s budgets. As such SLS has two key roles; Firstly, it needs to carry the hopes of a huge Apollo style project towards Mars for NASA and America, Secondly it needs to create jobs and bring prosperity to parts of the United States that would otherwise have suffered badly following the end of the Shuttle programme. It’s kind of difficult to work out which of these roles is deemed as more important, but less difficult to see which SLS is currently delivering on.

In January 2016 NASA’s independent Aerospace Safety Advisory Panel (ASAP) warned of “a continuing and unacknowledged accretion of risk” and a variety of issues leading to “an apparent erosion of safety” relating to SLS and the Orion spacecraft. These warnings sound far from reassuring regarding even the initial missions, but in response NASA has issued optimistic reports on the progress of the SLS and continues to herald it at every opportunity.

Conclusions
The SLS appears to face a number of major challenges between now and 2018. Firstly it needs to maintain progress towards the first test flight with no major slippages that will provide further fuel for its many detractors. Secondly, it needs to retain political support – an uncertain factor given that a new administration will be in place early in 2017. Finally, and perhaps most problematically, it needs to retain an impression of relevance in a world where advances in commercial launch technology seem to make it appear increasingly anachronistic with every passing month.

SpaceX recently announced its intention to use a Falcon Heavy to send an uncrewed ‘Red Dragon’ capsule to the surface of Mars during the 2018 launch window. It remains to be seen if they can meet this highly ambitious target, but even if they miss this it seems highly likely they will be able to carry out the mission in 2020. By the time SLS gets round to sending humans to Mars they may find a privately funded welcome waiting for them.

I recently commented on Twitter that I used to think I’d be able to count the amount of times the SLS would fly on the fingers of one hand, but I was now considering downgrading that estimate to the thumbs of one hand. ‘Recovering aerospace engineer’ Rand Simberg suggested I downgrade that estimate further to the thumbs of one foot. Personally, I still think the 2018 flight will take place – I’m just not sure cancellation is a fight the new President will want to pick with Congress so early, but as I’ve said, I’m no expert on American politics so I could well be wrong. I find it far harder though to imagine SLS still rolling on much into the next decade.

My huge worry with this is that NASA’s whole relevance, its whole reason for existing has become so intrinsically wrapped up in the Journey to Mars, that a cancellation of the SLS will deal the agency a blow it may not be able to recover from – what would NASA be then?

I’ve increasingly come to hold the view that NASA would be better served by getting out of the launch vehicle construction business and leaving that for others to provide as a service. Already we’ve seen NASA grant contracts for commercial cargo and crew resupply for the ISS. While this process hasn’t all been plain sailing, with both SpaceX and Orbital ATK suffering launch failures, at least it has allowed NASA to pick from a variety of approaches and contractors.

I hope NASA can return to something closer to the role the NACA used to hold for the aeronautics industry – helping conduct cutting edge R&D, then sharing the fruits of this with industry. The NACA never tried to build its own airline after all, but that didn’t make it any less effective in furthering the state of the art in aviation. Recently, we’ve seen new life breathed into two cancelled 1990s NASA concepts by private industry. The Bigelow BEAM expandable module, recently attached to the ISS has its roots in NASA’s TransHab research. SNC Space Systems DreamChaser spaceplane was developed from NASA Langley’s HL-20 concept. If SpaceX does make it to Mars in 2018, it will be with the support and assistance of NASA and benefitting from the data on the Martian environment accrued by various NASA missions. So I believe there is a huge future role for NASA in our exploration and exploitation of space. It just requires the support and leadership to move the agency in the direction where it can be most effective rather than most financially beneficial.

On any given day I can find articles supporting and criticising the SLS. This post has just been my attempt to work through some of my thoughts based on what I currently understand to be the situation. I’m quite willing to concede I may have inadvertently omitted certain factors or misinterpreted others. Certainly I’m aware that many hold views on this subject diametrically opposed to my own and I would never presume to claim my opinions are more valid. I welcome any ongoing discussion on the subject.

Advertisements

10 thoughts on “The SLS: A layman’s view

  1. Eric Ralph May 1, 2016 / 11:27 pm

    Wonderful article, I fully agree and have written an essay of my own awhile ago that criticized SLS and STS for very similar reasons. It would honestly be an incredible relief to see SLS cancelled ASAP, thus freeing many billions of dollars for some productive use.

    Like

  2. Pat Chiles May 2, 2016 / 11:16 pm

    Well said. It’s past time for private industry to take over access to LEO while NASA focuses on the necessary R&D to enable human expansion out into the solar system.
    Unfortunately it’ll probably take a programmatic disaster to force Congress to accept reality.

    Like

    • Anthony May 19, 2017 / 10:27 pm

      Porreca_Blog. I agree completely with the fact that NASA needs and is in the process of giving LEO missions to the private sector. However, this process will be a slow one. NASA is giving oversight to companies such as SpaceX to help their programs (rockets) be more reliable and efficient. Minus a blood priority the transfer will remain slow.

      Like

  3. DougSpace May 3, 2016 / 9:55 pm

    Whereas I generally agree with your perspective I think that there are a number of other things which should be considered.

    The lack of specific missions for the SLS is not the real problem. Say that the next administration comes in, keeps the SLS, but then lays out a set of missions at a flight rate of the Shuttle previously. We flew at that rate after the spending on the Shuttle development ended, why would we be unable to do the same after the expenditure on the SLS development ends. Now the SLS wouldn’t be a rocket to nowhere, now it would be the rocket to rotate irradiated crew from an EML facility. Does that make everything better? The problem isn’t the lack of a planned use for the SLS, the problem is that it is an inherently expensive thing to use.

    Second, say everything said against the SLS is true and the next administration cancel’s it. Now the money is freed up to develop those payloads for Mars…except that now we have no vehicle to get to Mars. So, the reason why the SLS has so much support in Congress goes beyond a few senators in a few districts. Those congressmen who don’t have a NASA center in their district still want the SLS because they want America to have the BLEO capability of going to places like the Moon and Mars. And they are not aware of how we can do that sans a HLV.

    So, if the SLS needs to be canceled then we need an alternative. A reusable Falcon 9 isn’t going to cut it. A partially reusable F9 has about a 30% reduction in payload to LEO and only a 30% reduction in price. Worse, at about 16 tonnes to LEO it would take about 57 of those to match the payload capability of the seven launches of an SLS Block 2 for a crewed mission to the surface of Mars. The logistics of 57 launches is ridiculous.

    OK, so use the Falcon Heavy. Unfortunately it seems as though SpaceX is discontinuing to use crossfeed on it so it will be limited to launching about 38 tonnes to LEO in its reusable form. That helps but that still means 24 launches per crewed mission to Mars. Perhaps my numbers can be quibbled with but the essence of my point remains.

    OK, so let’s hope for SpaceX to develop its own HLV (i.e. the BFR). Great! Hopefully SpaceX will have enough money so that it will get built and hopefully it will be fully reusable to boot. Great! But can you really blame congressmen from continuing with the SLS until it becomes clear that the possibility for a BFR is becoming a probability?

    Rather, I think that we need to consider near-term technical solutions. If the upgraded Falcon Heavy could have crossfeed, my calculation is that it would be able to deliver 93 tonnes to LEO. If we scale up current solar electric propulsion (SEP) then about 68.5 tonnes of payload could be delivered to an EML staging point for each launch of a FH. It turn out that this would be about 37% more payload to the EML staging point than even the SLS Block 2. Then when it comes time to send crew to the staging point, the relatively low-mass capsule could be quickly sent via something like a Delta IV Heavy, Falcon Heavy, or Vulcan.

    Extending crew stay at destination, recycling consumables, ISRU (especially propellant), and propositioning propellant are also approaches which could reduce the number of launches and hence reduce the costs for sustaining a growing base. So, my point is that we need to consider technical solutions and not just cast aspersions.

    Liked by 1 person

    • chrisbpetty May 4, 2016 / 11:21 am

      Thanks for taking the time to write such a detailed response. I guess my lack of faith in the SLS comes from the fact I find it hard to imagine the type of programme that could fully utilise such an HLV for a Mars expedition gaining the required government funding given how expensive each vehicle will be and the attendant costs surrounding the programme including ongoing development from the initial Block 1 spec to the more capable Block 2. I take your point that there is a wider willingness to support SLS in Congress due to a genuine wish to see America have a BLEO capability and not just because of the ‘pork-barrel’ politics, but was that not the case for Constellation and its predecessors as well?

      Currently I’m finding it difficult to get a full picture of exactly what a NASA Journey to Mars would entail in terms of vehicles. You mention 7 Block 2 SLS launches, NASA’s presentations certainly used to show 4 Block 2 launches and a recent post by Paul Spudis on his Lunar Resources blog mentions “between 8 to 12 launches of an augmented SLS” (he links to NASA’s Human Exploration of Mars Design Reference Architecture 5.0 doc from 2009 – I haven’t had time to check through this doc yet to find the reference). What is certain is that this won’t be a one rocket deal in the style of the Apollo landings although I’m not sure NASA’s various ‘public facing’ promotional materials for SLS/Journey to Mars have made this clearly apparent – possibly even to congressional representatives. Interestingly Spudis also mentions “some misleading promotional slight of hand” and maybe that’s what’s bothering me – when the mission is fully laid out with all of the requisite launches specced, will the price tag simply be too high?

      As for SpaceX and their Mars plans, I guess we’ll need to see what Musk unveils in Guadalajara in September. I suspect Falcon Heavy may be able to pick up some of the robotic planetary missions currently being talked about for SLS, but until it flies and we see if it lives up to the hype we can’t say for sure. I didn’t mean to suggest SLS/FH is an either/or choice, but I do think SpaceX can leverage economies of scale and reusability to keep costs down in a way SLS can’t.

      I’m really interested by what you say about near-term technical solutions. I find the idea of a Lunar COTS approach really intriguing and certainly a creative and progressive approach to solving many of the problems involved with BLEO activities and creating the necessary infrastructure to make things happen. It’s hard to imagine that public-private partnerships won’t play a key role in any expansion of human activities beyond LEO. I fully agree on the importance of ISRU and am encouraged to see awards NASA is making in this direction. I’m assuming that the fact your profile links to the Lunar COTS petition page that you are directly involved with this (Doug Plata?), so I wish you very success with the petition and again, I really appreciate you taking the time to share your knowledge and raise important points which I’d neglected to cover.

      Chris

      Like

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google+ photo

You are commenting using your Google+ account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

w

Connecting to %s