Single Stage to Orbit, Eventually

Stanley Kubrick/Geoffrey Unsworth's '2001: A Space Odyssey' (1968)
Shuttle flight deck, top; space station interior, bottom. “2001: A Space Odyssey” (1968)

A tip of the hat to Anthony Stevens, whose recent op-ed started me thinking about this week’s topics.

  • NoMoNASA
    Anthony Stevens, Anthony Stevens’ Weblog (November 25, 2022)

I’ll be talking about ideas that didn’t work out, or haven’t yet; three cool single-stage-to-orbit vehicles, including one that flew; and, finally, looking back and ahead. Or, rather, the other way around.

Plus, I’ve included short videos showing Skylon, the VentureStar, and a test flight of the McDonnell Douglas DC-X Delta Clipper prototype.

Beginnings, 1925-1968

Stanley Kubrick/Geoffrey Unsworth's '2001: A Space Odyssey' (1968)
Watching the news during a meal. “2001: A Space Odyssey” (1968)

Stanley Kubrick may not have known more about technology than the average film director, but he had the good sense to ask folks who did. I gather that’s why so much tech in his “2001: A Space Odyssey” (1968) looks familiar.

On the other hand, today’s chatbots aren’t nearly as smart as the film’s HAL 9000.

In the late 1960s, when “2001” was made, many computer scientists figured that we’d have human-like artificial intelligence within a few decades. Then they tried developing systems with human-like artificial intelligence, and that’s another topic.1

One reason we don’t have spaceships like the ones in “2001” is, arguably, because we’ve found unexpected technical problems along the way.

But I’m pretty sure we could have had equivalents of the film’s fully-reusable Orion shuttle by now. Along with at least one thriving boom town on Earth’s moon, and nuclear powered interplanetary ships like Discovery One.

We could, that is, if our world’s history had been different during the last 54 years.

“…Technology, however, does not proceed in isolated fashion, separated from the surrounding social, cultural, and economic environment….”
(“The Path to the Space Shuttle: The Evolution of Lifting Reentry Technology,” Introduction, Dr. Richard P. Hallion, (November 21, 1983) An AFFTC Historical Monograph, History Office; Air Force Flight Test Center)

I’d add “political” to Dr. Hallion’s list, although that’s arguably covered in his social and cultural categories.

A Fictional Spaceplane and Silbervogel, a Proposed Long-Range Bomber

Artwork by Karl Tate's artwork for '2001: A Space Odyssey:' Orion III spaceplane riding Orion I booster stage. Source: From Adam K. Johnson.'The Lost Science of 2001,' Christopher Frayling/'The 2001 Files' via
Orion III spaceplane riding booster stage “2001: A Space Odyssey” (1968)

The “2001: A Space Odyssey” spaceplane looks a lot like Eugen Sänger and Irene Bredt’s Silbervogel long-range bomber concept. To me, at any rate.

E. Sanger, J. Bredt's 'A Rocket Drive for Long-Range Bombers' (1944)
Silbervogel (Silverbird) concept sketch. (1944)

If that’s so, I don’t blame Kubrick and the folks publicizing “2001” for not highlighting where the filmmakers got their ideas for the shuttle.

The Silbervogel — “Silverbird” in German — had been part of Nazi Germany’s Amerikabomber program. That sort of publicity Metro-Goldwyn-Mayer didn’t need.

The Silbervogel would have been launched from a three kilometer long rail, just shy of two miles, accelerated to about 1,930 kilometers per hour by a sled drive. Then its rocket engine would take it to an altitude of 145 kilometers, 90 miles.

At that point, the Silbervogel would be going about 21,800 kilometers an hour.

That’s not quite orbital velocity, so the aircraft would drop back to the stratosphere, bouncing off our atmosphere’s denser layers. Then the Silbervogel would arc along until it hit the stratosphere again.

Its the same basic principle used in stone skipping.

A prototype Silbervogel was never built.

Which is probably just as well.

Seems that Sänger and Bredt’s mathematical model for reentry was a bit off.

As designed, the aircraft’s heat shield, along with the airframe, would have melted during its first reentry.

Correcting that problem would have let the heat shield — and the Silbervogel — survive. But the added weight would have made it dubiously useful as a bomber.2

Skip Entry
NASA's graph, showing 'the extent to which the Orion spacecraft's range can be extended with a skip entry, compared to the range the Apollo spacecraft was able to fly with a direct entry.' (2021)
Graph showing Apollo and Orion altitude/range reentry paths. NASA (2021)

If skip entry — non-ballistic entry in geek-speak — sounds familiar, maybe you read about it in coverage of Artemis I’s return last Sunday.

It’s what Orion, the Artemis crew capsule, uses to reduce stress during reentry.

The Silbervogel’s skip entry would have given it a range of between 9,000 and 24,000 kilometers, 12,000 to 15,000 miles.

That’s enough to carry it halfway around the world. Or would have been, once the aircraft’s heat shield was beefed up, and new technologies developed.3

But that didn’t happen.

Backing up a bit, the Silbervogel wasn’t the first proposed hypersonic vehicle.

Max Valier and the 1920s

Max Volier's rocket-propelled aircraft concepts. (ca. 1920s)Max Valier was born in Tyrol, Austria, Austria-Hungary, and Italy. Take your pick. That particular bit of real estate has changed hands and names a few times since 1895. I think it’s currently part of Italy.

Anyway, Max Valier was a technician, scientist, publicist or science fiction writer. Which of his many hats gets attention depends on who’s talking.

Or, my view, he was all of the above.

He also had what I see as a very good idea.

Along with some that were impractical for all but a few applications. Although his rocket-propelled cars might have helped raise interest, and funding, for his rocket-propelled transatlantic aircraft.

Valier’s idea was to design and built a series of aircraft, starting with what in the 1920s would have been cutting-edge propeller driven airliners with auxiliary rocket engines.

Then, step-by-step, each new version would get more of its power from rockets and have faster cruising speeds. Eventually, the airliners would be entirely rocket-propelled. And have top speeds that would make going into orbit an option.

That was Mas Valier’s idea.

I think it made sense. Back in the 1920s, demand for fast transatlantic passenger service was on the horizon.

Funding research and development with profits from Valier rocketliner passenger services might have been practical. After the Great Depression, anyway.

That didn’t happen, either. Max Valier stopped living, abruptly, in 1930. He had been a bit too close to an exploding rocket engine.

Instead, we got World War II, the Cold War and the Space Race. The latter fast-tracked a series of crewed expeditions to Earth’s moon.4

I don’t think the Apollo program was a mistake. Given the circumstances, it made sense.

But it did mean skipping over development of economically viable launch vehicles.

Hopes, Dreams and Weather Satellites

Thomas Voter's cover for Robert A. Heinlein's 'Rocket Ship Galileo,' Scribner's first edition. (May 1, 1947) Thomas Voter/Scribner, via Wikipedia, used w/o permission.Max Valier’s incremental development of suborbital and low Earth orbit rocketliners wasn’t entirely forgotten, however.

In R. A. Heinlein’s “Rocket Ship Galileo” (1947), for example, a professor and his youthful assistants refit a mail rocket with a thorium nuclear pile. Then, using zinc as propellant, they fly to the moon.

Heinlein was often careful when it came to science and technology in his stories, so I figure his novel’s vehicle might have reached the moon.

But I doubt that more than a very few folks could afford a DIY nuclear spaceship. And I am about as certain as I can be that leaving a trail of radioactive zinc would have broken several laws: by the time the technology became available, at least.

Even so, it was a good story.

Now, going back what we got instead of Max Valier’s gradual development of low Earth orbit passenger and freight service.

The Space Shuttles, while the fleet was in service, were partially re-usable; which made lofting equipment and people into space a trifle less ruinously expensive.

But there weren’t enough Shuttles to satisfy demand for launch services.

In the 1980s there weren’t as many communications, navigation, weather and other Earth observation satellites as there are today. But we’d learned how useful they could be.

That warranted development of single-use launch vehicles ranging from Japan’s SS-520 to America’s Saturn V.

And standardized miniature satellites like CubeSats — are yet another topic.

As for the hopes and dreams of folks like Max Valier and stories like “Rocket Ship Galileo,” I see significant connections between science fiction and the history of aerospace tech.5

Single-Stage-to-Orbit: Two That Never Flew, One That Did

J. Philip Drummond (NASA Langley Research Center Hampton, VA, United States), Marc Bouchez (MBDA Bourges, France), Charles R. McClinton (NASA Langley Research Center Hampton, VA, United States): 'Overview of NATO Background on Scramjet Technology,' Chapter 1, Figure 1. (2006) from NTRS - NASA Technical Reports Server, used w/o permission
From a summary of scramjet technology in development. NASA (2006)

We still don’t have an equivalent of Max Valier’s rocketliner. But we’re getting closer to a single-stage-to-orbit spaceplane’s test flights.

I’ll be taking a quick look at two of my favorites. And the McDonnell Douglas DC-X: which isn’t a spaceplane, but did make several test flights.6


(video, music 6:45)

Reaction Engine Limited’s Skylon hasn’t been the only only air-breathing single-stage-to-orbit spaceplane that made it past concept art.

But it’s the only one I’ve been following that’s still in development. I think it helps that Reaction Engines Ltd. offers products and services that are available today.

The basic idea behind Skylon and other air-breathing spaceplanes is using oxygen in Earth’s atmosphere for the first few minutes of flight. Then, in Skylon’s case, at Mach 5 or so the spaceplane’s engines switch over to oxygen stored in its tanks.

That means less oxygen for Skylon to carry onboard, and more payload/cargo capacity.

It’s smart, efficient, and requires technology we don’t have yet. The last I heard, Reaction Engines Ltd. is still developing Skylon’s SABRE engines.7

Venturestar and X-33

(video, music 9:13)

NASA Marshall Space Flight Center's photo: a test of twin Linear Aerospike XRS-2200 engines, originally built for the X-33 program. (August 6, 2001)
Linear Aerospike XRS-2200 engines being tested at Stennis Space Center, Mississippi. (2001)

I like the The Lockheed Martin VentureStar. A lot.

It looks cool, and its linear aerospike rocket engine is cool technology. Or will be, once it’s out of the research and development stage.

I figure that’ll happen, eventually. A linear aerospike rocket engine is a close cousin to the aerospike or plug nozzle rocket engine.

In both cases, instead of burning fuel and oxidizer inside a roughly bell-shaped tube, aerospike rocket engines do their combustion on the outside of a roughly cone-shaped spike. Or, for a linear aerospike, on either side of a tapered bar.

Maybe that sounds crazy, but it works.

Or did, at any rate, when the folks at NASA mounted half of an X-33 lifting body mockup with a linear aerospike on an SR-71 Blackbird. That was in 1998.8

Nozzle Shapes, Ideal and otherwise
NASA illustration showing what happens when ambient pressure is at, above, and below a rocket nozzle's exit pressure.

The ideal shape for a rocket engine’s nozzle changes as air pressure changes.

Eventually someone may develop a bell nozzle rocket engine that changes shape as air pressure changes.

How, I’ve no idea, since we keep today’s engine nozzles from melting by running comparatively cool fluid through them. The plumbing’s complicated as it is.

Aerospikes would be the right shape at all altitudes and pressures, since the outer wall of the combustion chamber is the burning fuel-oxidizer mix. And, while in at atmosphere, the surrounding air.

Keeping the aerospike from melting can be tricky. I gather that’s one reason the Lockheed Martin and NASA folks decided to go with the X33/VentureStar linear aerospike.

Then they dropped the project.9

And that’s yet again another topic.

Delta Clipper

(video, sound 2:48)

The McDonnell Douglas DC-X, the prototype test model for its Delta Clipper, had the elegant lines of a pallet tank.

The roar of its engines would have given noise abatement activists conniptions.

I think it was the closest we’ve come to a commercially viable single-stage-to-orbit vehicle.

McDonnell Douglas saw the Delta Clipper as a cargo carrier. Which is a good thing, since it would have reentered Earth’s atmosphere nose-first: leaving passengers hanging head-down, barring a rotating passenger section.

The DC-X and Delta Clipper needed no next-generation technology.

The DC-X test vehicle flew, landed and was prepped for its next flight by a crew of 38; operating out of a 40-foot trailer. Turnaround time was around 26 hours.

The idea was to develop a workhorse cargo ship, and show that operating a freight run to low Earth orbit could be as straightforward as any other long-distance freight service.

Then, thanks at least in part to NASA’s increasing role in DC-X development, the prototype was refitted with new technologies.

The DC-XA, renamed the Clipper Graham, flew four more times.

On its fourth and final flight, July 31, 1996, the Clipper Graham took off and flew perfectly. But only three of the craft’s landing legs deployed.

That wasn’t enough to keep the DC-XA upright. So when the engines stopped it fell over, caught fire and was destroyed.

One version of what happened was that NASA’s demands for new technology and paperwork hadn’t set well with the DC-XA crew. Neither had on-again/off-again funding and threats of cancellation. And that was the end of the Delta Clipper.

But not the end of folks having a shot at turning cargo and passenger service to low Earth orbit into an extension of our existing transportation network.10

Our Moon, Mars and Someday the Stars

Photo: Virgin Galactic's Spaceport America. (2017)
(Spaceport America, southern New Mexico. (2017))

A few decades after Max Valier’s shared his dreams of transatlantic rocketliners, passenger and freight air service between Europe and Americas was routine.

A century later, air travel isn’t newsworthy unless something goes spectacularly wrong.

Assuming that the 2020s are pretty much like the 1920s, I could also assume that a few decades from now we’ll have routine spaceline flights on the Earth-Luna run. And that a century from now the first expeditions will be returning from the Alpha Centauri system.

That, I am quite sure, won’t happen. Not over the next century.

I figure that transatlantic air service of the 1930s was possible because there were already comparatively wealthy countries on both sides of the ocean.

Right now, there’s nobody living on Earth’s moon. That will very probably change in a decade or so.

But Lunar settlements NASA and other space agencies are planning sound like today’s Antarctic bases. I think we’re a long way from settlements that will grow into cities like Boston and Charleston. More than a few decades, anyway.

Tracy Caldwell Dyson's photo: self portrait in the ISS Cupola module, Expedition 24. (2010) From NASA/Tracy Caldwell Dyson, via Wikimedia Commons, used w/o permission.That said, I think that we will keep visiting our moon, follow robotic pathfinders like Perseverance and New Horizons, and find reasons for settling down on or at least near other worlds.

And that some of us will look at this wonder-filled universe and remember wisdom we’ve been passing along through the millennia.

“What are humans that you are mindful of them, mere mortals that you care for them?
“Yet you have made them little less than a god, crowned them with glory and honor.”
(Psalms 8:56)

“Terrible and awesome are you,
stronger than the ancient mountains.”
(Psalms 76:5)

“Yours are the heavens, yours the earth;
you founded the world and everything in it.”
(Psalms 89:12)

“Indeed, before you the whole universe is like a grain from a balance,
or a drop of morning dew come down upon the earth.”
(Wisdom 11:22)

Historical Perspective, Technology and the Kardashians

Joseph Keppler's 'The Bosses of the Senate' cartoon, first published in Puck Magazine. (January 13, 1889) This version by the by the J. Ottmann Lithographing Company, via Wikimedia Commons, used w/o permission.
“The Bosses of the Senate” cartoon by Joseph Keppler. (1889)

I think the folks at McDonnell Douglas had the right idea, keeping their Delta Clipper’s tech simple. And letting flight and ground crews concentrate on doing their jobs.

But I can see the NASA brass viewpoint, too. Part of NASA’s job is developing new technology, so tricking out the DC-X probably made sense to them.

As for demanding paperwork (apparently) above and beyond the call of reason? NASA is part of a bureaucracy. A government bureaucracy, at that. Paperwork is inevitable.

So, maybe, was cancellation of both the DC-X and X-33/VentureStar programs.

The first because it was far too straightforward for NASA at the time.

The second because developing linear aerospike technology involved more cost and time than NASA could afford. Or sweet-talk Congress into supporting.

The good news, as I see it, is that folks like Elon Musk are still allowed to try using what’s already been invented, develop new technology, and — eventually — make the Earth-to-orbit run as routine as transpacific flights are today.

That, again as I see it, is a good reason for letting individuals earn more wealth than I’ll ever see.

Although putting up with ‘Kardashian’ headlines is an annoyance.

But if it also means that we get individuals like Andrew Carnegie, Jacques Cousteau and Elon Musk? That, arguably, is worth the annoyance.

'Robber barons,' before the phrase became common. John Leech's 'Punch' cartoon: 'How to Insure Against Railway Accidents. Tie a couple of Directors à la Mazeppa to every engine that starts a train.' (March 26, 1853)On the other hand, I know why we changed the rules, back when folks were getting fed up with train wrecks and exploding boilers. And with those 19th-century American businessmen who acted as if America’s Congress was on their payroll.11

I think both laissez faire capitalism and no-hold-barred socialism look good on paper. And that neither is a good idea.

I’ve talked about that, technology, spaceships and being human before. Often:

1 Imagining the future, 1968:

2 Silbervogel in context, very briefly:

3 Somewhat-technical stuff:

4 A hop, skip and jump over late 19th and 20th century topics:

5 Transportation tech and satellites by the bushel:

6 Single-stage-to-orbit research, mostly:

7 Reaction Engines Ltd and Skylon:

8 A promising new technology:

9 Aerospike efforts:

10 DC-X, the Delta Clipper; I think this could have been in service today:

11 Private-sector people, perceptons and operations:

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About Brian H. Gill

I was born in 1951. I'm a husband, father and grandfather. One of the kids graduated from college in December, 2008, and is helping her husband run businesses and raise my granddaughter; another is a cartoonist and artist; #3 daughter is a writer; my son is developing a digital game with #3 and #1 daughters. I'm also a writer and artist.
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