The Delta Clipper (McDonnell Douglas DC-X) achieved vertical landing two decades before SpaceX's Falcon 9. And its cost was very low — only 60 million dollars.

Why was such an awesome rocket cancelled? How is NASA trying to reduce costs when they invested billions in SpaceX and Boeing and United Launch Alliance (ULA) but did not continue investing millions in the Delta Clipper?

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    $\begingroup$ For reference, 60m USD in 1991 is equivalent to about 118m USD today once you correct for inflation. That's still not super expensive for a rocket, but it's almost twice what it sounds like at first. $\endgroup$ – Austin Hemmelgarn Aug 4 '20 at 16:54

The cancellation of the Delta Clipper project ultimately was about about NASA politics rather than technological value, but even so, it probably wouldn't have been a great launcher.

According to Wikipedia:

NASA had taken on the project grudgingly after having been "shamed" by its very public success under the direction of the SDIO. Its continued success was cause for considerable political in-fighting within NASA due to it competing with their "home grown" Lockheed Martin X-33/VentureStar project.

First, note that the 60 million dollar development was not for Delta Clipper itself, but for DC-X, which was a scaled down technology demonstrator.

DC-X was tiny and carried no payload, and could not get anywhere near orbit; its liftoff mass was about 19 tons.

The proposed DC-1 orbital Delta Clipper would have a liftoff mass of around 470 tons, and take 4.5 tons to LEO. That's a 1% payload fraction; 2%-3% is more typical for two-stage launchers.

Astronautix has the DC-1 launch price estimate at \$350 million 1991 dollars (\$660M 2020 dollars), which seems very steep; I don't know if they're accounting for reusability there.

Atlas V carries twice the payload at a quarter of the price. Falcon 9 FT carries 3 times the payload at a 10th of the price.

Even if Delta Clipper's reusability had cut launch costs dramatically, it still wouldn't be competitive with two-stage-to-orbit expendables and partially-expendables -- single-stage-to-orbit rockets just can't carry much payload.

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    $\begingroup$ While the economic points of DC vs. staged rockets are valid, NASA didn't pursue those either...they poured funding into the X-33 project instead, and it would have had similar issues (if it had any payload left over after fixing its tank problems). DC lost because of not-invented-here politics and because they already know how to build it...NASA actually used the fact that it didn't require major new technologies to be developed as a basis for rejecting it: they wanted a big R&D-heavy project instead. (Which eventually bit them when those composite tank problems cropped up...) $\endgroup$ – Christopher James Huff Aug 3 '20 at 21:24
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    $\begingroup$ Also, the Delta Clipper was proposed to have a turnaround time of 3-7 days. By comparison, the Falcon 9 has a record turnaround of 51 days (arstechnica.com/science/2020/07/…). A higher launch rate could have made the Delta Clipper competitive. $\endgroup$ – Pitto Aug 4 '20 at 1:21
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    $\begingroup$ @Pitto: You are comparing the proposed turnaround of DC to the current actually fastest turnaround of F9. For a fair comparison, you should either use the proposed turnaround of F9 (less than 24h) or the actual fastest recorded turnaround of DC. The fact that SpaceX has, as of yet, not turned around boosters faster does not necessarily mean that they can't. Another likely explanation is that they don't have enough customers to require it. For redundancy reasons, you want more than one booster in your fleet. For reasons of wear and tear, you want to rotate them evenly. So, the only … $\endgroup$ – Jörg W Mittag Aug 4 '20 at 9:24
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    $\begingroup$ @JoeJobs: For SpaceX to get to a launch cadence where they need to refly F9s in less than a day, they would need to have as many launches alone per year as the entire industry has had in the last 5-10 years combined. I just don't see that happening. Even if they wanted to launch the entire Starlink constellation on F9 within one year, they would just barely get to that. It would also mean that they need to crank out second stages at a rate of two per day. $\endgroup$ – Jörg W Mittag Aug 4 '20 at 18:00
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    $\begingroup$ @JoeJobs Do you have anything to support your assertions that "There would be even more companies launching satellites …"? The launch cost is just a fraction of the total cost of ownership of a satellite (first you need to design and build it, then you need to support its operation for years). Also, the reason they aren't launching Starlink faster might have a lot to do with the fact that producing 60 brand new hi-tech satellites every two weeks might be a little difficult. $\endgroup$ – TooTea Aug 5 '20 at 8:41

The DC-X was not built by NASA but by the DOD. After the DOD was done with it, it was transferred to NASA.

"Built as a one-third-size scale prototype, the DC-X was never designed to achieve orbital altitudes or velocity, but instead to demonstrate the concept of vertical take off and landing."

(emphasis mine)


The DC-X achieved its goals. When it was destroyed in an accident, there was no compelling reason to rebuild it.


The DC-X was small, at 4 meters diameter, with a payload capacity of only 3000 lbs. \$60 million only bought the concept prototype. To build the necessary preproduction and production models could have brought the total costs into the billions. Still not out of the question if the rocket was capable, and that was a large problem, it was not. As a single stage sub orbital rocket with small payload it was never envisioned to be comparable to the shuttle or falcon 9. Small payload, low ceiling equals limited utility.

To date no single stage rocket has ever reached orbit. Huge research dollars to achieve a single stage orbital rocket were cost prohibitive in the Bush Sr. era when the US defense department budget would be cut 10% in 4 consecutive years. Then cut again under early Clinton. (The Cold War was over).

NASA was holding out for a more traditional more capable rocket like the Aries V or SLV.

How is NASA trying to reduce costs when they invested billions in SpaceX and Boeing and ULA but did not continue investing millions in Clipper?

As for NASA “wasting” money on SpaceX, I would say when the Space Launch Vehicle finally launches it will cost over \$2 billion per launch with no re-use, added to the \$19 billion development cost. Added to the \$230 billion cost of its failed predecessor the Constellation program which failed to deliver its Ares V rocket (predecessors of the SLV) before being canceled in 2010. The \$60 million per launch of the falcon 9, developed with private money, is a bargain. When the new larger Starship comes online, also developed with mostly private money, its launch cost is projected to be only \$2 million (SpaceX costs) for more than 4 times the payload of the Falcon 9. Any money NASA spends with SpaceX in my book is a bargain.


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