Space Cover #181: HL-10 Lifting Body Cachets
In my previous Space Covers of the Week, we looked at cachets on the X-15 covers, and also cachets from the M2 series of lifting body rocketplane covers. This week, let’s look at the Northrop HL-10 lifting body rocketplane cachets.
The HL-10 was another wingless configuration that looked favorable for a future Space Shuttle vehicle. In profile the HL-10 was flat on the bottom with a curved top, much like a conventional airfoil wing (as opposed to the M2 which was basically a half-cone). An all-metal HL-10 was built by Northrop along with the M2-F2 lifting body.
The HL-10 first flew on December 22, 1966 on a glide flight in the hands of NASA test pilot Bruce Peterson. The top cover in the above image is postmarked at Edwards, Ca on that date. It carries a rubber stamped "First Flight" cachet, with a hand lettered "HL-10 Bruce Peterson" added by the servicer. The Bruce Peterson script autograph below that is not part of the cachet.
The lower cover shows the Northrop Stamp Club printed cachet for the flight, postmarked near the Northrop plant in Hawthorne, Ca. that day. Again, the Peterson autograph is not part of the cachet.
After this first flight, the HL-10 project stood down for over a year, working to correct some stability issues experienced on the flight. In the meantime Bruce Peterson was seriously injured in a crash of the M2-F2 lifting body. Jerry Gentry, a USAF test pilot, took his place on the HL-10 project. The second HL-10 flight took place on March 15, 1968 in the hands of Gentry (top cover above). By that time the cover servicer (I’m thinking Boy Scout Troop 141, but if someone knows differently, please shout!) had developed a rubber stamp cachet reading "HL 10 LIFTING BODY". Then they hand wrote Gentry’s name in below – please don’t confuse this as a Gentry autograph – you will see these for sale, falsely listed as "autographed". This type of cachet was used up through the fifth flight on May 3, 1968.
For the sixth flight on May 16, 1968, a new rubber-stamped cachet appeared (lower cover above) showing a profile view of the HL-10. This is generally acknowledged as the "Boy Scout Cachet", applied by the local Boy Scout Troop 141, for the HL-10 and was used through the last flight on July 17, 1970.
Bob Rank got in with a gorgeous, one-off Velvet Cachet for the November 13, 1968 powered flight of the HL-10 (above). Rank’s cachet lists this as the first powered flight of the HL-10, however it was the second powered flight. The earlier, first powered flight just didn’t go so well…
Anyway, in the words of the test pilots themselves, the HL-10 ended up being the easiest-to-land lifting body. Several of the flights were dedicated to proving that the future Space Shuttle could land "deadstick" without extra landing engines. In the Shuttle era, an HL-20 variant was formulated to be a potential crewed orbital re-entry vehicle, but that was eclipsed by the more-extensively-characterized X-23/X-24 lifting body configuration that we will discuss next time.