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Edgar Zapata's avatar

From a longtime NASA LaRC engineer:

Good post, Edgar.

Planned flight tests of new "government-led" launchers and spacecraft are fewer and farther between these days than they were in previous human spaceflight programs, such as Apollo. I've wondered before about why this is. One possibility is that due to the improvements in analytical modeling and computational capabilities over the years since the 1970's, program managers are confident that a more streamlined flight testing campaign can be sufficient, essentially, skipping some tests. "Today we can do more for less, and quicker, than the old days," would be the claim. It can also help to sell a new program when the availability of funding is a major factor, which it has been for decades now. This is just the impression I've had. I want to say that I've actually heard these things stated before in meetings, but I may have misinterpreted or imagined that.

If this "we can do things better than we used to" line of thinking is the underlying rationale, are people really just fooling themselves?

As I've mentioned before, we often consider Apollo to be the gold standard for how to do a human spaceflight program right. On the topic of heat shield testing, in Apollo there were two tests of the CM heat shield at simulated lunar return conditions prior to any crewed flights. The first utilized a Saturn IB to launch a fully-functional Command Service Module on a suborbital trajectory. This test was designated AS-202. With the help of the service module, the reentry velocity was increased to over 19,000 mph. Not quite up to a lunar return, but still a useful demonstration.

The CM heat shield would be tested again without crew on Apollo 4 (AS-501). This was the first all-up flight test of the complete Saturn V and Apollo spacecraft system. In this case, the heat shield was tested at actual lunar reentry conditions (~25,000 mph). One thing that I just noticed when looking this up is that the heat shield was a Block II design, whereas AS-202 flew a Block I design intended for returns from Earth orbit. The results of AS-202 had been used to improve the Block II design, which was intended specifically for the lunar missions. There are similarities here with Orion heat shield development, but without the issues encountered by Artemis 1.

With the success of Apollo 4, the way was clear for crewed flights. The first of these was Apollo 7, which spent 10 days in LEO. Apollo 8 went all the way to lunar orbit and back.

I think your proposed new plan holds up pretty well. However, if we were to follow the example from Apollo, the first flight of an SLS Block 1B for Artemis IV would be without crew. In addition to the heat shield demonstration, Apollo 4 simulated the translunar injection burn. The SLS B1B w/EUS represents a new configuration compared with Block 1. There is some additional risk involved in utilizing this for the very first time to send Orion to the Moon with crew onboard.

Concerning the Starship lander development, the leaked acknowledgment that a human landing would be delayed to late 2028 should, logically, be factored in. This does open the possibility to redefine the early Artemis missions. You may recall that Jim Free, lead of ESDMD at the time, made some comments a few years ago to this effect. https://spacenews.com/nasa-weighs-changes-to-artemis-3-if-key-elements-are-delayed/

Note that Free thought at that time in mid-2023 that Artemis 2 would fly by November 2024. The heat shield issue from Artemis 1 (mostly) changed that. Everything has been slipping for a while.

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