Space X meet the McDonnell Douglas DC-X Vertical landing circa 1992

Alot of fan fair has gone to Space X and it's vertical landing. In 1992 McDonnell Douglas was doing the vertical landing already.

I found that back in the 1990's McDonnell Douglas was doing vertical landings, although it was never designed to go into orbit, only show the technology in vertical landings and take offs.

I wonder how much tax payer funds were sunk into McDonnell's craft? And I hope Space X didn't reinvent the wheel when the basic goal had been reached in 1992.

a reply to: seasonal

McDonnell Douglas is now Boeing, who is a SpaceX competitor. They're not going to share any data they have from the Delta Clipper with SpaceX.

a reply to: Zaphod58

If there were patents, they went bye bye in 17 years. So they wouldn't have a choice. And there are engineers out there who were let go you could take that knowledge with them.

My point is the tech is old. Space X just climbed a mountain 25 years after Mc. did.

a reply to: seasonal

Most of the data is proprietary company data. A number of companies and agencies have built rockets that land vertically over the years, not just McDonnell Douglas. Even if one company builds one, it's not necessarily the same as another's rocket. If you look at the Delta Clipper, it had four rockets spread around the base to use for landing, one at each corner. The SpaceX rocket uses a central motor system, which reacts differently.

a reply to: seasonal

There are many technical differences between the DC-X and SpaceX’s flyback booster that makes a direct comparison of the two of them somewhat meaningless.

The DC-X was a technology demonstrator for what was supposed to be a Single Stage To Orbit (SSTO) launch vehicle. By definition, an SSTO vehicle has to go all the way from the launch pad to Low Earth Orbit (LEO) and back. For that reason, it has to have a shape that is pretty good at rising up through the atmosphere (starting from zero and ending up at about 8 km/sec) AND good at re-entering the atmosphere (going from 8 km/sec down to zero) without burning up. You can see that the shape they chose is kind of a rounded conical shape with a cone half-angle of about 10 degrees and a hemispherical nose. The shape is actually a scaled-up version of an advanced nuclear warhead entry vehicle design that was called AMARV.(See, for example, en.wikipedia.org...). With an approximately 10-to-1 ratio between length and diameter, this makes a reasonable good shape for a launch vehicle (similar to the Saturn booster, for instance).

The DC-X, like the AMARV utilized body flaps during re-entry to control the angle of attack and the roll angle, aerodynamically. This is the same strategy that was used on Space Shuttle and would have allowed it to fly similar entry trajectories—meaning it could fly thousands of kilometers cross range and maneuver to a precision landing point. The AMARV was highly tested and analyzed by McDonnell Douglas, so there was a lot of confidence in its feasibility as an entry vehicle. That was an important factor in its selection.

Just like the Shuttle, an SSTO vehicle shaped like the DC-X would have decelerated from its entry velocity all the way down to its terminal velocity entirely aerodynamically (in other words, without consuming any propellant). At the time it would have to pitch up and begin its terminal descent to landing, it would have been going less than Mach 1. The rocket thrusters on DC-X were highly throttleable, meaning that the thrust-to-weight ratio when the landing descent began was just slightly greater than 1-to-1. This means that soft landings were very easy, since you could just slowly turn down the thrust level and allow the vehicle to settle slowly on the pad.

In the SpaceX case, it is only the first stage that flies back to the launch site. The first stage is basically just a cylinder—not streamlined at all. It doesn’t have a good enough lift-to-drag ratio to fly very far aerodynamically. The strategy that SpaceX uses is to perform the major course maneuvers with propulsion, not aerodynamics. That allows them to avoid adding lots of different gadgets like body flaps and simply carry more fuel (which is cheap). In order to do their turn around maneuver, they have to fire their rocket motors after the second stage has separated and the first stage is nearly at its highest speed. Also, they have to fire the rockets directly into the oncoming, supersonic airstream. That’s called supersonic retropropulsion. Supersonic retropropulsion had never been demonstrated on a large scale until SpaceX did it in 2014, and NASA considered it to be a difficult and scary problem.

The second problem is that the SpaceX booster did not have deeply throttleable engines. That means that they have to land with thrusters that have a thrust-to-weight ratio much greater than 1. They have to time the landing burn very precisely so that they scrub off all the descent velocity exactly and then turn off the motors at the exact moment they touch down. Otherwise, they start ascending again and then crash.

Overall, the SpaceX soft landing was much more technically difficult than the DC-X landing. SpaceX hired engineers that worked on DC-X, so they knew what the DC-X program had learned and then they took it to the next level.

a reply to: seasonal

Not sure about SpaceX, but Blue Origin had actively recruited former McDonnell Douglas and Boeing personnel who had worked on the DC-X project as far back as 2005.