Why were there three and Four Finned Aerobees?

[K38]

Why did they make both 3 and 4 finned Aerobees? The launch tower at Wallops was built for four finned rockets and the others were for three finned rockets, Did they feel that the east coast winds needed extra stability? Or did they just get ahead of themselves and build the first tower without asking the rocket guys. I would love to build a scale model of the Aerobee tower, but I bet it would be a real job.

Thanks,

Dwight

[blackshire]

Materials I've read about the Canadian (Bristol Aerospace) Black Brant sounding rockets said that the four-finned Black Brant VC (BBVC) offered greater stability with longer payloads (with less "coning" as the rocket spun during powered ascent, if memory serves) than did the three-finned Black Brant VB (BBVB). The four-finned Aerobee 150A, 170A, 200A, and 300A may have embodied this same advantage over the three-finned Aerobee 150, 170, 200, and 300. (The 22" diameter, four-engined Aerobee 350 was only built in a four-finned version, as far as I know.)

[MarkB.]

Actually, it was launch rails: There were three-finned towers at White Sands and Ft. Churchill and four-finned at Wallops Island. The later, larger Aerobee 350 were launched from standard launch rails rather than the towers. The three-fin launch tower at White Sands may have been a modification of the original WAC launch tower but that is only a supposition

Performance was the same for the 150 or 150A as minor thrust variations from rocket to rocket could and would overshadow any drag effects of the extra fin.

[Mark II]

But then the question is, why didn't the three agencies arrange to use a single standard launcher design? Oh, wait - 3 separate agencies, each with a limited budget - OK, now I get it. Never mind.

[blackshire]

Actually, it was launch rails: There were three-finned towers at White Sands and Ft. Churchill and four-finned at Wallops Island.I'm not sure if this was the reason. I've seen pictures of three-finned Aerobee 170s and four-finned Aerobee 170As (both of which used Nike motors as boosters) on single-rail surplus Nike-Ajax launchers (which were much shorter than either the 3-fin or 4-fin Aerobee towers). Also, if memory serves, I've seen a photograph of a three-finned Aerobee 150 on a Nike-Ajax launcher.The later, larger Aerobee 350 were launched from standard launch rails rather than the towers.Are you sure? (I'm not trying to start an argument here.) If you're referring to the largest Aerobee of them all (22" in diameter and powered by a cluster of four Aerobee 150 engines, with a Nike motor used as its booster), I have never seen photographs or drawings of anything other than the four-finned Aerobee 350 (which had "single-wedge" cross-section fins), and Aerojet sent me everything they had on it. All of the Aerobee 350 launch photos I've seen showed the rockets being launched from the 4-fin towers at Wallops and White Sands.The three-fin launch tower at White Sands may have been a modification of the original WAC launch tower but that is only a supposition.I'd have to dig out my copy of Peter Alway's "Rockets of the World" to be sure, but if I recall correctly the WAC Corporal tower was only 100' tall and was torn down soon after the program ended. However, I'm sure the larger 3-fin Aerobee towers were based on the WAC Corporal tower since the original Aerobee (Standard Aerobee) itself was essentially a scaled-up WAC Corporal with a more refined aerodynamic shape.Performance was the same for the 150 or 150A as minor thrust variations from rocket to rocket could and would overshadow any drag effects of the extra fin.Agreed. Since the four-finned Aerobee "A" versions often flew with longer payloads, though, I wonder if they (like the four-finned Black Brant VC versus the three-finned Black Brant VB) had less "coning" than three-finned Aerobees with similar payloads would have had during the spin-stabilized powered ascent? That could account for the development of the four-finned Aerobee 150A, 170A, 200A, and 300A.

[MarkB.]

Blackshire,

I'm with you. You're right about the 350s being launched from towers, but I am unaware of a four-fin tower at White Sands. You could be right, its just I've never seen it nor can I recall pictures of it. A three fin Nike and three fin 350 might have worked but I'm just guessing.

I've not seen a 150 on a Nike launcher, but I have seen a picture (somewhere in the attic) of a 170 on a Nike launcher.

[K38]

I think the 4 fin tower was at Wallops Island

DLB

[Bill]

Could it be that four fins are used when the intended payload was lighter (less nose weight?)


Bill

[blackshire]

Regarding the 4-fin Aerobee towers, here (see: http://www.postwarv2.com/BBV/ ) is a photograph of a Black Brant VC being launched from the 4-fin Aerobee tower at the White Sands Missile Range. This tower can also be seen well in the background of this photo (the fourth down from the top one, see: http://www.postwarv2.com/BBIX/photos.html ) of the Consort 1 launch (a Terrier-Black Brant VC, also called the Black Brant IX). This 4-fin Aerobee tower may still exist (although I don't know); the one at Wallops Island was torn down some years ago.

The "Old Timers Bulletin Board" on the White Sands Missile Range Museum web site (see: http://www.wsmr-history.org/index.htm ) might have members who could definitively answer these "Why?" questions about three- and four-finned Aerobee rockets and towers. Also, here are some good pictures of the Aerobee 150A (see: http://www.postwarv2.com/aerobee150A/ and http://www.postwarv2.com/aerobee150A/photos.html ) and Aerobee 350 (see: http://www.postwarv2.com/aerobee350/ ). The main rocket photo list is here (see: http://www.postwarv2.com/moreRockets.html ). I believe the Aerobee 150A in the above-linked photos is the one that carried a French VLF (Very Low Frequency) experiment--it was depicted in "Rockets of the World" by Peter Alway.

Bill's question "Could it be that four fins are used when the intended payload was lighter (less nose weight?)" could be the key to this three-finned vs four-finned Aerobee issue. Atlantic Research Corporation produced several sounding rockets that used surplus Honest John and Nike rocket motors. For their three-stage Honest John-Nike-Nike, they offered two third stage fin sets--a set of four standard upper-stage Nike trapezoidal fins and a special third stage Nike fin set intended for use with lightweight payloads. This special fin set consisted of four moderately swept-back clipped delta fins with swept trailing edges, and they had "single-wedge" cross-sections like the Aerobee 350's larger fins. Unlike the three-finned Aerobees that had double-convex cross-section fins, the four-finned Aerobee 150A/170A/200A/300A had fins with "single-wedge" leading edges, flat cross-sections behind the leading edges, and blunt (square-cut) trailing edges. These Aerobee fins are more like the "single-wedge" special Honest John-Nike-Nike third stage fins made for use with lightweight payloads.

[MarkB.]

Awesome!

At White Sands, the three fin towers were at Launch Complex 35 and launched Aerobee 150 and 170 and Black Brant VB. Two towers, both torn down in the mid-80s.

The four fin tower was at LC 36 and launched Black Brant VC. Google Image seems to indicate that the tower here still exists. I could not find a record of any Aerobee launches of any type from this site.

Early Aerobees were launched from LC33, the same site as the V-2 and WACs. This is now a National Historic Site.

The records show at least 12 Aerobee 350 launches from White Sands through 1982 but do not say from which LC

I used astronautix and the WSMR sites as sources.

[blackshire]

Awesome!

At White Sands, the three fin towers were at Launch Complex 35 and launched Aerobee 150 and 170 and Black Brant VB. Two towers, both torn down in the mid-80s.There was also a 3-fin Aerobee tower (now long gone) at Eglin Air Force Base, Florida. In addition to launching Aerobees, Marshall Cartledge (one of the USAF Eglin AFB sounding rocket personnel) told me that the Eglin AFB Aerobee tower also launched a few three-finned Iris sounding rockets (they were just like the three-finned HYDRA-Iris sustainers but with the Atlantic Research Corporation seven-motor clustered finless boosters instead of the three-finned, triple-Sparrow motor HYDRA-Iris boosters). This tower had three "braking loops" that extended upward and outward above the normal launch rails. The fly-away rail-riding "shoes" on the sub-caliber Iris rockets (which were narrower than Aerobees) separated from the rockets as they exited the tower and traveled up and then down the "braking loops" until they bumped to a stop at the top of the tower.

An enclosed 3-fin Aerobee tower (which looked a lot like the 4-fin towers at White Sands and Wallops) was also built at the Churchill Rocket Range near Hudson Bay in Canada. The upper portion of the tower that protruded out of the launcher building was also enclosed at first, but the panels on the tower were later removed. This tower also launched single-stage and multi-stage Black Brant sounding rockets. It may still exist, but I don't know.The four fin tower was at LC 36 and launched Black Brant VC. Google Image seems to indicate that the tower here still exists. I could not find a record of any Aerobee launches of any type from this site.A few Aerobee 350 rounds were launched there, including the final Aerobee 350 in 1984, which carried an ultraviolet astronomy payload. This LC35 tower (like the 4-fin Aerobee tower at Wallops) also launched the solid propellant 15" diameter Astrobee F sounding rocket (Aerojet's intended "drop-in replacement" for the 15" diameter liquid propellant Aerobees, which used Aerobee payload modules and launch shoes). The wider and more powerful Black Brant V eventually beat the Astrobee F in this sector of the sounding rocket market.Early Aerobees were launched from LC33, the same site as the V-2 and WACs. This is now a National Historic Site.Was this the tower with "wider-stance" symmetrical support legs that appears in early Aerobee launch photographs, or was that the Holloman Air Force Base Aerobee tower (which was also a 3-fin tower)? The two 3-fin towers at White Sands' Launch Complex 35 had "narrower-stance" support legs and looked like the tetrahedron formed by each tower's legs was narrower on one "face."The records show at least 12 Aerobee 350 launches from White Sands through 1982 but do not say from which LC

I used astronautix and the WSMR sites as sources.I'm pretty sure they were all launched from the 4-fin tower at LC35. The Aerobee 350 was bigger (22" in diameter as opposed to 15" for all other Aerobee versions) and heavier than other Aerobees (but it used the same Nike booster as the Aerobee 170/A and 200/A), which would have made an Aerobee 350 launch from a shorter, single-rail launcher "interesting" (in the Chinese curse way), especially on windy days... :-)