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U.F.O. Redux - Surprise!

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It’s 1963 ... and the USAF has just found out – to its great consternation – that UFOs are real and they really are abducting people.

Despite strenuous efforts by Colonel Edward Straker to keep the security lid on this situation, the news leaked out and the public and politicians demanded that the USAF should “do something” about this (the hysterical demands by the politicians might have to do something with the abduction of a junior Congress member who nobody really missed before the leak).

Much shouting, screaming and running around in circles ensued.

The Navy – not to be outdone by the early successes of the USAF in this new battlefield of the continual inter-service warfare – starts to pour serious money into a little known company named General Atomics and appoint Admiral Hyman Rickover as liaison, later as program chief. This will a few years later result in the primacy of the Navy for all operations outside the Earth-Lunar space – much to the chagrin of the USAF.

The civilian space program is directed to cooperate closely with the military – NASA's budget doubles overnight and NASA basically turns itself into the USAF's R&D department...the results of this will be a much accelerated space program, although one geared mostly to produce a space station and space based interceptors fast.

The USAF also starts an immediate crash program to make its anti-aircraft and ABM missiles and its high performance interceptors capable against this new threat. Upgrades of any kind to the different Nike batteries leave the production companies almost on a daily basis.

However it was quickly realized that the existing defences were woefully inadequate – the performance of the aircraft interceptors was insufficient, the missile batteries too static and space based interceptors were still several years away.

Something was needed to plug the hole – and quickly. This resulted in the birth of the ISF (Interim Space Fighter) program.

The Interim Space Fighter (ISF) – aka S-1A&B Eagle:

The only aircraft in existence that barely had enough performance to reach space was the X-15 – at that time employed in a very successful testing program. All three existing airframes were pulled off the testing program and hastily modified into the X-15B to test its suitability as a “pop-up” space fighter.

The major changes were:

1. Lengthening of the aircraft immediately behind the cockpit in order to change the test instrument bay located there into a second, very cramped cockpit for a weapon system officer.

2. Changing of the forward section of the side strakes into weapon bays. The selected weapon was a variant of the nuclear armed Genie missile – the SIR-1A (Space Intercept Rocket) a.k.a. SSSG (Spin Stabilised Space Genie).

3. Integration of an intercept radar and weapon control systems – a AN/APG-50 “stolen” from the F-4 Phantom II. This was then successfully “married” to a digital computer that was a result of NASA's Gemini project, calculating the orbital parameters of the SIR-1A's flight path.

4. Lengthening of the airframe aft of the wing to increase tank volume and to counteract CoG shifts created by the additional cockpit and the radar and weapon systems.

5. Increasing the wingspan and wing area and beefing up of the landing gear to deal with the increased landing weight.

6. Improvements to the thermal protection system to handle the increased re-entry temperatures.

7. Increasing the drop tank volumes to raise peak altitude and adding a destruct system to them in order to prevent impact of intact tanks in civilian areas. This destruct system proved to be a rather controversial addition, continuously discussed until the end of the program. As opinions differed if it would be better to have a larger piece of debris impacting a single spot or scattering smaller, but still dangerous pieces over a wider area with more targets.

The result of these changes was an aircraft that was somewhat larger and had a markedly higher launch weight – capable of a much higher apogee then the original X-15.

General characteristics:





X-15B / S-1A








15.47 m


17,08 m



6.8 m


7,1 m



4.12 m


4,12 m

Wing area:


18.6 m²


20,3 m2

Empty weight:


7,766 kg


8,985 kg

Loaded weight:


16,069 kg


18,973 kg (without droptanks)





2 SIR-1A / B

Powerplant: 1× Thiokol XLR99-RM-2 liquid-fuel rocket engine, 313 kN, later LR99-RM-5








Maximum speed:


Mach 6.70 (7,274 km/h)


Mach 6.70 (no speed tests made)



450 km


850 km (nominal at max. height)

Service ceiling


108 km


177 km

Rate of climb:


18,000 m/min


18,000 m/min

Wing loading:


829 kg/m²


 831 kg/m (empty fuel tank)

The intended mission profile was for the S-1 to be moved by its carrier aircraft close to the ground track of an orbiting UFO after detection by ground based sensors. If the orbit data was not of sufficient quality to calculate flight parameters, the B-36S would then use its own search radar to refine the orbit – however the preferred mode was to launch “silently”, using only the ground sensor data and to use the B-36S search radar only to provide attack assessment.

After a successful launch and pop up manoeuvre above the atmosphere the fighter would activate its own radar, make final calculations and fire a salvo of two SIR-1A at the target, hopefully bracketing the UFO. Landing would then be at any military or civilian airport in range and with sufficient runway length.

The tests with the X-15B were highly successful and in fact the two X-15B's remaining intact after testing were pressed into service until the S-1A's were fully deployed. The production of the service version, designated S-1A Eagle, was started immediately after the modifications of the X-15A’s were finished – during the X-15B's testing phase - in order to save time. Service experience with the S-1A resulted in a later upgrade to the B version.

Carrier aircraft:

During development it was soon realized that – although the B-52 had enough payload capacity – the duration of a patrol was severely limited by the endurance of the X-15's pilots sitting for extended periods in a cramped cockpit.

A solution for this problem was necessary and found in an aircraft that had been decommissioned only a short time earlier. The B-36 has a crawl space in the wing allowing the flight engineer access to the engines in flight. The pylon for the X-15 was modified to enclose the cockpit area and connected to the engineering crawlspace – making it possible for the X-15 crew to board their aircraft in flight.

The still existing and mothballed B-36 units were quickly brought back into service and updated during the refits. It was found that additional changes were made possible by the huge payload capacities of the B-36 – the refitted versions received the designation B-36S.

These changes were, in addition to the wing pylon for the X-15, a huge isolated LOX tank in the former bomb bay to fill and top off the X-15's LOX tank in flight, search radar in a bubble on top of the aircraft and a computer to generate flight parameters for the X-15 from the radar information.

Air-to-air refuelling gear (probe and drogue type) and engine updates (both of the piston engines, but especially the jet engines) were also added to the B-36 in order to increase the possible patrol endurance. The B-36 were crewed with 16 men working in two shifts, plus the ISF crew. The longest combat patrol on the record took an astounding 109 hours.


The whole program was rushed through in a war time mode and it took only a little longer than a year until the first patrol flights were started in 1964.

Surprisingly enough the whole system worked rather well despite having been improvised on a rush base and the huge B-36 carriers became a visible - and also very audible sign - that the authorities were indeed “doing something”. They also gave the USAF an opportunity to operate not only over US territory, but also to extend some marginal protective cover over the territories of allied states, which proved to be a great boon to US foreign policy.

The ISF was kept in operation until 1979 – long even after space based interceptors became available due to its operational flexibility, visibility to the public and diplomatic utility.





Enemy action




4 lost

1 lost




37 lost

48 lost








UFO landing craft

UFO motherships

















 All USAF test pilots that originally were with the X-15 test program volunteered to serve with the ISF, as did several of the civilian test pilots – Scott Walker became the first space ace, with a total of one mothership and four landing craft.

Chuck Yeager also pushed his way into the ISF program, using his political connections, and proved to be still as deadly as during his Korea war time, becoming the third space ace. Unfortunately he also become one of the casualties of the ISF program, when the mothership he was successfully engaging managed to launch a landing craft immediately before his attack, which then retaliated against him.


The ISF system filled the gap until the first real space interceptors came into production in 1968, however the USAF's initial concentration on a “fast solution” made it possible for the Navy to steal a march on the USAF by designing and testing a drive system suitable for large spaceships with long endurance.



Appendix: SIR-1A SpaceGenie aka SSSG (Spin Stabilized Space Genie)









2.95 m


2,95 m



0.44 m


0,44 m



1.02 m


not applicable

Launch weight:


373 kg


387 kg



Mach 3.3


1.250 m/s delta vee



9.6 km


not applicable



Inertial (None)


Inertial, proximity fuse

 Warhead: W-25 nuclear fission, 1.7 kiloton yield - this was soon upgraded to the SIR-1B with a W-44 warhead with 10 kt yield and a delta vee of 1.480 m/s, or the massively tritium boosted W-44B warhead with 22 kt (although this warhead was VERY expensive to procure)



Appendix: Differences between the S-1A and B versions

The S-1A Eagle was a direct copy of the X-15B, slightly tweaked to make serial production a little bit easier – serial construction started already at a time where the X-15B was still in testing, in order to speed up deliveries.

The B series was built some time later, after some operational experience had been gained. All A series spacecraft were upgraded to the B standard during major overhauls.

Neither the A nor the B series really had a definite configuration – all ISF fighters were constantly been tinkered with, pieces of equipment were often added or changed on an experimental basis. This constant tinkering made the S-1 ground crews probably the most versatile and experienced in the whole USAF.

Externally the B version was identical to the A version or the X-15B. The main changes happened “under the hood”, making the B version quite a bit more versatile and powerful.

Main differences were:

Improved engine: The series version of the XLR-99 offered slightly better thrust, a larger throttle range, more inflight engine restarts and an Isp improved by 5 seconds. The engine also mounted an altitude compensating engine bell. All these changes were achieved while reducing the engine weight slightly and keeping the overall engine size identical.

Improved tanks: The B series received a small “tank inside the tank” as reserve. Unless the pilots had to use up all fuel – including the reserve - during ascent and combat manoeuvres, this reserve fuel allowed them to restart the engine for a few seconds after re-entry to “stretch” their dead stick glide back to an airfield – a very good and lucky pilot would even be able to do a whole go around and second landing attempt. The “tank inside tank” design was chosen in order to keep the reserve fuel cold during re-entry.

Larger APU and improved electric system: to power the advanced avionics and ECM systems of the B series

Avionics and ECM: in this area perhaps the greatest improvements were made to the B series, with constant upgrades and changes throughout the lifetime of the S-1. The S-1B received not only upgrades to its radar – especially higher pulse strength - but also several generations of on-board computer, with countless software versions.

The B version carried only one missile on a substantial number of flights – additional ECM systems or intelligence sensors were carried in the other missile bay during such flights. The development of the larger APU was partially driven by these demands.



Appendix: Diplomatic repercussions of ISF program

Perhaps the greatest diplomatic achievement of the ISF program was an increased cooperation between the US and the CCCP – after the existence of UFOs had become public knowledge, a secret conference in Vienna resulted in sharing of all the information available at that time and ensured that the teletype “hot line” installed after the Cuban Crisis was used to exchange real time orbital parameters of UFOs.

A short time later the Cosmonaut treaty was extended to space fighters in hot pursuit of UFOs, giving them emergency landing rights on Warsaw pact territory and vice versa and guaranteeing prompt return of crew and spacecraft – something that was used and honoured several times by both sides.

This cooperation – and the existence of a common foe – ensured that the cold war became a lot less nerve racking affair and may ultimately have been one of the factors that lead to today's CoDominion, safeguarding peace on Earth and its colonies.

As soon as sufficient numbers of S-1 and carrier B-36S for a defence of the North American continent had become available, landing rights for rest and refuelling were arranged with most nations not being members of the Warsaw pact. The continuous presence of ISF flights over North and South America – and them being based there - did a lot to enable US diplomacy to quieten down the permanent political crises in South America and paved the way for the GNAU – Greater North American Union - to come into existence after 2002.



Appendix: The Navy during the UFO crises

The USN realized very early during in the crisis that the USAF was initially much better positioned to respond – so it decided to temporarily pass the lead to the air force while still keeping its fingers in the pie by sending a large number of navy aviators to the ISF, where they were very effective indeed.

The USN also started a crash program to convert a substantial number of ships to act as mobile bases for Nike Zeus / Spartan / Spartan Hoplite missiles, which like many other ground based interceptors were only partially successful.

But these activities were only a smokescreen to obscure the real aim of the USN – to gain dominance in trans-lunar space over the USAF.

To achieve this the Navy gave serious funding to General Atomics, who were at this time busy developing the Orion nuclear pulse drive concept under the leadership of Freeman Dyson. The Orion concept proved viable and design and production of a prototype space battleship (codenamed Project Michael) was started with Admiral Rickover acting as a military project head.

Another reason for the Navys success was the creation of its advisory panel on long range strategy, which consisted to a large degree of well known SF-authors. Chairmanship of this panel soon devolved on the former naval officer R. A. Heinlein, who held this position for a long time until his emigration to L5 colony.

The approval of the funds for Project Michael in the US Congress is still under discussion by historians, as very many documents and files pertaining to this mysteriously are missing in the records.

The USSS John F. Kennedy was launched in 1974 on top of its Seadragon lofter stage and on its shakedown cruise engaged and destroyed two UFO motherships in the battle of L2.

Later, larger Orion drive ships opened up the entire solar system to the human race. The ultimate success for the USN came when in 2001 one of the UFO motherships was detected coming out the Rabbit Hole, the jump point inside Mercury’s orbit. This not only pointed towards a solution for the riddle of the alien's FTL drive, but also finaly offered a way to give good protection to the entire solar system, not only to specific planets or installations.

STF 1 (a.k.a. The Rabbit Hunter Squadron) soon established a continuous observation and later blockade of the jump point and also enabled scientific research of the jump point, leading to the discovery of the Alderson jump drive.