Speed-record X-15A-2, in 1/48th

[dhanners]

Here’s my build of the X-15A-2, 66671, as it appeared on 3 October 1967 when Pete Knight set the world speed record, hitting Mach 6.70, or 4,520 mph.

The model is a YukonJohn redesign/repaint of Henry Yuen’s X-15, enlarged to 1/48th scale. I used my normal building and scratchbuilding techniques. Nothing extraordinary.

One note on the white X-15A-2…. As many of you might know, the white coating was a sealant used to cover the ablative, MA-25S, which was dark pink. When exposed to liquid oxygen, MA-25S had a nasty habit of exploding if a tool or something heavy was dropped on it. To prevent that, the ablative was covered with a sealant.

Technicians sprayed on the sealant, but on the underside of the wings and tailplanes — where the threat of a dropped tool was pretty low — they weren’t too worried about full coverage. So the underside of the wings and tailplanes show a patchy appearance, with pink showing through. It shows up pretty well in color photos from the flight.

I replicated this look by borrowing one of the grandkids’ watercolor sets, mixing up some pink, then dry-brushing it on with a cotton swab.

[jparenti]

I honestly did not know the underside has patchy places!

[dhanners]

Originally Posted by jparenti

I honestly did not know the underside has patchy places!

Indeed, I’ve certainly never seen it modeled before. But the splotchy look is clear as can be in photos, and I ran it past X-15 expert Michelle Evans (author of The X-15 Rocket Plane) and she said that when it came to sealing the ablative on the bottom of the wings and tailplanes, technicians didn’t get anal about covering everything.

This is from her website. I’ve added the yellow ovals….

[Kazziga]

I love your obsession with X-15s ;-)

[dhanners]

Originally Posted by Kazziga

I love your obsession with X-15s ;-)

Thanks. I think I’ve got a couple more X-15 builds in me, but as YukonJohn will attest, I’ve said that before….

Last night it struck me that I failed to add the optical glass port on the ventral sensor bay, as well as a couple of equipment/experiment boxes attached to the rear of the rudder. So I added them.

[dhanners]

An X-15A-2 Mystery…. While building my model of Pete Knight’s world speed-record flight of 3 October 1967, I came upon a mystery. The X-15A-2 carried a dummy scramjet on the ventral stabilizer (a bad idea, as it turned out) and based on photos from the flight, I modeled the nose of the scramjet in white.

But I came across another photo — also said to be from the flight — showing the nose as a darker color, a type of orangey red. So which was it — white or orangey red?

As far as we know, the white X-15A-2 flew twice. On 21 August 1967, Knight flew it (without external tanks) on a test flight, hitting Mach 4.94. It carried the dummy scramjet, which then had a carried a distinctive black stripe along the side and a white nose. Then in October, with external tanks attached, Knight set the speed record at Mach 6.70.

I contacted author and X-15 expert Michelle Evans to see if she could clear up the white vs. orangey red issue. She said she had no definitive answer, but it would seem the nose of the scramjet on the record flight was orangey red; there’s at least one photo of the vehicle in flight showing it. Adding to this evidence is a post-flight photo of the recovered scramjet, which was jettisoned prematurely and hit the desert floor quite hard. Although the photo is black and white, the nose appears a darker color than the visible white portion of the structure.

So where did the photos of the white-nose version come from? She said one possibility is that there was a captive flight of the ‘A-2 with empty tanks before the speed record flight, but there’s no documentation of such a flight.

One interesting note: As the X-15 program wound down in 1967-68, photographic coverage of X-15 flights was harder to come by. NASA had little photo coverage of Knight’s record flight. In fact, Knight even hired his own photographer to document the flight.

So my model went back to the workbench to paint the nose and add the double-spiked sensor it carried. Fortunately for me, the technicians who painted the nose of the real dummy scramjet did it freehand, so the lines weren’t exactly straight.

[dhanners]

I think the “mystery” is solved. The X-15 Flight Log shows that mission 2-C-93, flown on 7 August 1967, was a scheduled captive flight of the X-15A-2 with full ablative coating, dummy scramjet AND external tanks to test the effects of cold-soaking the vehicle.

That would explain the discrepancies….

[-Jim G]

David,
your wholes series of X-15 models intrigues me. Thank you for sharing!
You have a keen sense of detail.

[dhanners]

Decided my X-15A-2 looked bare without its external tanks (although they were only attached for about a minute on the actual vehicle’s flight) so I added tanks re-sized to 1/48th scale from Ken West’s “In-Flight” version.

Ken’s tanks come in a white-and-silver scheme that represent, as best I can discern, silver-and-bare metal dummy tanks that never flew. The tanks used on Pete Knight’s speed-record flight were far more colorful — and each was different.

Both had noses in Dayglo Red/Orange, but the left tank was silver and white with a black end dome, and the right tank was silver with a black band, and a black end dome. Both had a camera-target spiral on them. There were other distinctions; the left tank had some irregular silver stripes inboard, while the paint on the nose of the right tank was chipped, exposing some of the natural metal underneath.

I have zero repainting skills or capability, so to replicate the tanks, I used colored cardstock. Ken’s parts were used as templates and I cut parts out of a red/orange cardstock, as well as silver, white and black cardstock. I used Ken’s tank domes but colored them with a black marker. I plumbed them with fuse wire.

[mbauer]

Originally Posted by dhanners

Decided my X-15A-2 looked bare without its external tanks (although they were only attached for about a minute on the actual vehicle’s flight) so I added tanks re-sized to 1/48th scale from Ken West’s “In-Flight” version.

Ken’s tanks come in a white-and-silver scheme that represent, as best I can discern, silver-and-bare metal dummy tanks that never flew. The tanks used on Pete Knight’s speed-record flight were far more colorful — and each was different.

Both had noses in Dayglo Red/Orange, but the left tank was silver and white with a black end dome, and the right tank was silver with a black band, and a black end dome. Both had a camera-target spiral on them. There were other distinctions; the left tank had some irregular silver stripes inboard, while the paint on the nose of the right tank was chipped, exposing some of the natural metal underneath.

I have zero repainting skills or capability, so to replicate the tanks, I used colored cardstock. Ken’s parts were used as templates and I cut parts out of a red/orange cardstock, as well as silver, white and black cardstock. I used Ken’s tank domes but colored them with a black marker. I plumbed them with fuse wire.

Awesome looking.

Mike