In 90s, NASA was thinking big — not Apollo programme big, but big nonetheless. By then, the now legendary space shuttle was coming to be around two decades old, had served reliably on 34 missions and was a marvel of 20th Century engineering. NASA however, was already looking at the next logical technological step after the Space Shuttle: SSTO.
SSTO stands for Single Stage To Orbit. Basically, it means a vehicle that’s a single unit and is the same when it launches and returns — unlike the rockets we’re still using today. Today’s rockets, even those fancy SpaceX ones, ‘split up’ at some point(s) of their journey; this is done to reduce ‘dead weight’, that is, used-up fuel tanks, payload coverings, spent boosters etc. If our current rockets were cars they’d shed their doors and windshields to save weight as they go, while SSTOs would be like real/common sense cars: you have the same amount of car at the beginning and end…hopefully.
Many engineers, scientists and futurists thought that single stage spacecraft would be commonplace by the 2000s, and unlike most people predicting the future, they had good reason. NASA, along with a bunch of private companies had already started work on the space shuttle replacement: an SSTO called VentureStar.
VentureStar was ambitious. By ambitious I mean sci-fi movie ambitious, which you could tell if you just looked at it. It was triangular and looked more like a plane than a spacecraft — with stubby wings and stabilisers it also landed like a plane.
But Why Look to Replace the Shuttle?
The Shuttle was meant to reduce the cost of getting stuff into space, based on the simple fact that money is saved if you reuse something rather than make a new copy of it every time it’s used. Problem is — it wasn’t that cheap. When proposed to the US Congress for funding in the 70s, NASA projected that the cost of sending a 1 Kg payload to LEO (Low Earth Orbit) with the shuttle to be around $260. For contrast, the SpaceX Falcon Heavy — which has one of the lowest launch costs to LEO, will set you back $2350 per Kg.
$260/Kg is ludicrously unrealistic even during the 70’s but NASA had to bend the truth in order to get funding.
There were quite a few factors as to why the glorious Shuttle cost so damn much:
Super — complicated engineering incurs super — high costs
Imagine being a technician. You’re tasked with replacing the square shaped tiles on the bottom surface of the Shuttle — easy, right?
Nope. The picture above makes it look like you can put a tile anywhere, but if you did that it would lead to a bunch of dead astronauts, a PR nightmare, hundreds of millions in damages and costs, and a big red X on your CV. The Space Shuttle had some 35,000 tiles — and each one could only be fitted at a specific point
Additionally, there was the fact that the complicated RS-25 engines had to be taken out and the core components cleaned thoroughly with early versions requiring full disassembly — every single time the Shuttle flew.
Short-sighted politics
A lot of the maintenance work was split up among many private contractors which were spread out through the USA. This was done to make it appealing to politicians from those states where shuttle activities were based since it led to job creation and state prestige. However, this led to increased costs due to greater logistical complexity and the fact that maintaining a supply chain consisting of multiple companies is harder than when only one is involved.
Lower-than-expected launch rate
It was hoped the shuttles would fly some 12 missions per year, but this was reduced to an average of 4.5 due to maintenance schedules among other reasons. While this didn’t increase the actual cost of the program, more launches would have led to a lower cost per launch — meaning a better return on investment.
VentureStar Looked Like the Perfect Solution
Unlike the shuttle, VentureStar was a single unit; there were no external fuel tanks and boosters that had to be replaced for every mission. In theory, this meant an even lower operational cost and possibly quicker turnaround.
Also, it had a revolutionary new engine design called an ‘aerospike’, which is basically like a traditional bell-shaped rocket nozzle folded in on itself:
VentureStar was a spaceplane, this meant that once it had completed its mission it would land on Earth like an ordinary aircraft. The Space Shuttle was similar in terms of how it landed but since it couldn’t launch itself into space it can’t be called a true spaceplane.
The wide triangular body of the VentureStar was large enough to generate its own lift (a body that generates lift is called a lifting body), so it didn’t need wings as large as the Shuttle which meant less weight. Also, the heat-resistant tiles used a new mounting method that would have saved 17,000 man hours in maintenance alone.
The wide lifting body also meant that it could enter the atmosphere slower, since it would encounter more air resistance. This in turn meant that the tiles would encounter less heating from the crazy levels of friction that occur when something enters the planet’s atmosphere. A slower entry speed also meant a smaller runway could be used for landing — increasing the potential number of landing sites.
There were also environmental considerations. The VentureStar would use LOX (Liquid OXygen) and Hydrogen for propulsion, a much cleaner choice than the solid rocket boosters strapped each side of the Shuttle.
The Bigger the Ambition the Bigger the Problems
Composite tank issues
Like the Space Shuttle, VentureStar suffered from some major technical short-sightedness in its early stages. Lockheed Martin proposed to use fuel tanks made of composite materials such as carbon fibre, this was a sore point for the engineers. Composite materials were not good enough to be used as fuel tanks since they had to store very cold liquids which led to the tanks rupturing from thermal stresses and air seeping in.
The engineers knew this would be too much hassle and forced management to allow them to build aluminium tanks as well — just in case.
Turns out the engineers were right. The composite tanks burst during pressure tests and thus the aluminium tanks were used instead. Interestingly enough these tanks were lighter than the proposed composite ones
The aerospike engine was too ambitious
The novel new engine design was meant to save costs and offer better performance over the full flight profile. While it was a great engine in theory, it required complicated cooling in order to function and this meant a large amount of extra weight.
A victim of politics
In the end, the entire project was cancelled due to a combination of factors, the largest being that while the it was possible to have a working VentrureStar at the time, albeit with less advanced tech than was hoped for, the project was biting off more than it could chew.
NASA chose Lockheed’s design because it was so ambitious, but that’s also precisely why it was shot down — it couldn’t deliver all those innovations and cutting edge technology.
NASA has had many ‘paper rockets’, and the VentureStar is one of them; something that only existed on paper but never in reality.
If this spacecraft hadn’t been swept away in a torrent of mismanagement and political gymnastics, human spaceflight may have advanced leaps and bounds. However, on the flip-side, its absence may have helped speed the transition to private spaceflight and the proliferation of space capabilities that we have seen occur in the past few years and will see for many to come.
