"Spiral" of the development of aerospace systems

Exactly 40 years ago, having separated from the Tu-95KM carrier aircraft, the MiG-105.11, which received the nickname “bast” for its characteristic shape, set off on its first single flight . It was an analogue of an orbital ship, created as part of the Spiral aerospace system , along which an accelerator aircraft should also have been created, capable of accelerating at 6M and two rocket stages to put the ship into orbit. As a result, only the ship and several copies of it were madeon a scale of 1: 3 which flew into space. Despite this, the “Spiral” and the American project X-15, which were originally from the 1960s, turned out to be closest to the completion of all projects of air launch of space cargo at the moment.

Difficulties in creating an engine for a hypersonic accelerator aircraft ( GPVRD ) and chronic bad luck pursued such projects. And even now, when it would seem the appearance of the first scramjet workers ( X-43 and X-51 ) opened the way for space for such projects, the appearance of reusable first stages (from SpaceX , Blue Origin and India) seems going to finally put a bullet in the history of these projects. What was stopping them all the time? This will be discussed below.

Theory

Why is an air launch so beneficial? The fact is that it allows you to save in the mass of the rocket due to the fact that part of the speed and altitude is covered by the accelerator aircraft (that is, it reduces the required reserve of the characteristic speed or delta-V), it also allows you to immediately put on the first missile stage of the LRE with vacuum nozzles which have a larger specific impulse , which increases the efficiency of the engine and also reduces the weight of the rocket. At the same time, aircraft engines such as turbojet ( turbojet ), ramjet ( ramjet ) and even hypersonic ( scramjet ) - although they have a specific impulse that decreases with increasing speed, but it still remains significantly higher than that of a rocket engine up to 10 sound speeds (10M ):



In addition, until 1993, landing a rocket stage on engines seemed too complicated and was not considered as a promising direction for reusable space systems. So the vast majority of reusable projects up to this point somehow relied on the design concept with wings or a bearing body and horizontal landing.

Comparison of the benefits of an air launch from the maximum speed of the booster:
As can be seen from the table, a speed of 6M allows you to save a third of all expenses for reaching a low reference orbit ( NOO ), which for a three-stage rocket means that when you start from such a hypersonic aircraft, we can actually throw out the first stage (which introduces the maximum share in the total launch vehicle cost). For speeds of the order of 2-2.5M, two passenger aircraft and countless military were built, and even for speeds just above 3M, at least one aircraft (about which below) was manufactured in the USSR and the USA, the characteristics of which allowed to carry a significant load. At the same time, at such speeds we still have 20% savings from the required speed.

It would seem that a subsonic start saves a lot (up to 10%) - but in this case several problems appear at once: in order to get the maximum benefit when starting with a limit of ≤1M, we need to climb as high as possible. But due to the drop in air pressure at altitude, the stall speed (minimum speed) of our aircraft begins to grow, while the speed of sound (maximum speed), on the contrary, begins to fall. The most revealing in this regard was the reconnaissance aircraft Lockheed U-2, which climbed to a height of 21 km. At a cruising speed of 805 km / h, it had a safe speed window of only 19 km / h (after upgrading the aircraft, its safety window became even smaller), the exit from which threatened to stall or even destroy the aircraft. The pilots were given the very colorful name “grave angle” that converges with a height increase of one point to this graph of safe values , partly because three test pilots died due to this effect when testing the aircraft . It was possible to put up with such a danger for a strategic reconnaissance, but for an ordinary commercial “space cab” - this proves an excessive risk.

Thus, all modern air launch projects are limited by the practical ceiling of transport aircraft, usually 10-12 km. At this altitude, the LRE vacuum nozzle still has significant losses in efficiency, which means a slower launch and greater losses at the time of launch (when the proportion of losses is already the highest). Therefore, we need or use with specially designedfor such large differences in altitude, engines or make an engine with an “intermediate” nozzle. This forces us to actually make a specialized launch vehicle for air launch that will not have unification with ground samples, or to use the currently existing components of ground launch missiles that are not optimal for air launch and thus lose a significant part of its advantages.

Preexisting projects:

The X-15 rocket was



dropped from under the wing of one of the two B-52 bombers allocated for this at an altitude of 13.7 km at a speed of about 800 km / h. After that, the rocket launcher launched its rocket engine on ethanol / oxygen components and, depending on the flight plan, gained maximum height or speed, after which it planned to the bottom of the salt lake and sat on the front wheel rack and two rear skis. There were three rocketplanes in total: 1) X-15-1 - the base model that completed 82 flights; 2) X-15A-2 - a version that made a total of 53 sorties, on which additional reset tanks and ablation protection were installed during the flights, with which William Knightwas able to reach a speed of 7247 km / h in flight No. 188; 3) X-15-3 - the version used for high-altitude flights, on it in flights No. 90 and 91 Joseph Walker was able to climb to a height above 100 km - beyond the generally accepted border of space ( Karman line ), no one else could do this for 199 flights 3 rocket planes.

The flights lasted from June 8, 1959 to October 24, 1968, after 6 transfers of the 200th flight due to various reasons, it was canceled along with the entire program on December 20, 1968. In flight No. 4 on November 5, 1959 to Scott Crossfieldhad to crash due to a small fire. Not designed for landing with full tanks, the X-15-1 rocket plane broke, but the pilot was not injured. It took 2.5 months to repair the damage. In flight No. 74 on November 9, 1962, the X-15A-2 rocket engine could not reach full power, which was why it was decided to land in an unplanned place and exceeding the limits in mass and speed, which caused the rocket plane to flip over and catch fire , pilot John Mackay received serious injuries. The X-15-3 rocket plane was completely lost in flight No. 191 on November 15, 1967, when it entered a tailspin when entering the atmosphere, pilot Michael Adams died. Both remaining intact X-15s are now on display in museums.



X-15 could hardly reach space (which is now easily doingNew Glenn starting from the ground) since his fuel was far from ideal, having a specific impulse of only 276 seconds. This allowed the rocket plane to have a reserve of characteristic speed of 2.4 km / s - much less than the minimum required to enter orbit 7.8 km / s. But for this problem there was an elegant solution: it was supposed to develop deltoid wings designed for high speeds for the X-15-3 rocket plane, and the rocket plane was going to be launched with an additional rocket stage from the back of the Valkyrie XB-70 strategic bomber. New wings for the rocket plane were purged in the wind tunnel from 1966 until the X-15-3 disaster, which put an end to this idea.



The flight tests of the two Valkyries built were normal until October 14, 1965, when the first model, when tested at a speed of> 3M, the incoming air flow tore 60 cm of its honeycomb structure from the left wing. The speed of this prototype, it was decided to limit M = 2.5. During joint demonstration flights of the second Valkyrie and F-104 Starfighter samples , on July 8, 1966, the latter sucked and hit the Valkyrie wing with a turbulent flow. Piloting the F-104, Joseph Walker (setting an altitude record on the X-15) died on impact, the Valkyrie fell into a corkscrew from the damage and crashed, one of its two pilots was unable to catapult and also died.

The flights of the remaining Valkyrie continued until February 4, 1969, with speed limits, until this project was completely closed by the then Secretary of Defense Robert McNamara, along with another noteworthy project - the X-20 Dinosaur spacecraft .


In parallel with the dumping of rocket-planes, the “Stratospheric Fortresses” B-52 participated in the tests of NASA vehicles with a bearing hull named “flying bathrooms” for their shape and mediocre aerodynamics - ships of the M2-F1 , M2-F2 and M2-F3 series (in the center). As Milton Thompson spoke about this aircraft: “If a person fell out of the B-52 at the time of the separation of the M2-F1 from the aircraft, the device would be ahead of him at the Earth.” Aerodynamics were further improved, due to which the HL-10 (on the right) and X-25A (on the left) appeared, but all of these devices had only small engines and were intended exclusively for the study of aerodynamics during descent from orbit, which ultimately formed the basis of the Space design Shuttle " . So the record for all three devices was the results in 1976 km / h in speed and 27524 m in height shown on the HL-10 in flights on February 18 and 27, 1970, respectively.

"Spiral"



The heart of the program was to become a hypersonic accelerator aircraft, which was supposed to develop 4-6M. At the beginning, they wanted to entrust this project to the Tupolev Design Bureau (the Tu-144 already working at that time ), but in the end he refused it. The project was adopted by Mikoyan Design Bureau, which purged aircraft models in a wind tunnel until the project was closed. The accelerating aircraft was accelerated with the help of an accelerating trolley to a speed of 400 km / h, after which it started its engines and took off from the ground. To improve aerodynamics after takeoff, the nose of the aircraft rose, thereby limiting the view to the bottom - this option was used on the Tu-144 and Concord , and for the Soviet bomber T-4 went even further and made the cabin completely closed.

Since the base fuel for rocket stages (fluorine / hydrogen) and fuel for the scramjet of the booster aircraft (hydrogen) were not used for this purpose before, it was decided at the initial stage to develop an intermediate version of the system with slightly worse performance. However, even this intermediate version was supposed to be, in many respects, the best that was created before, and the main version of the system is absolutely amazing:
Thus, this system could put into orbit a load of 10+ tons with a launch weight of only 115 tons - that is, the payload was about 10% of the launch weight! This is simply an unthinkable indicator for modern chemical rockets, which put into orbit an average of 3.5% of their own mass (and only in the heaviest version of the fully hydrogen Delta IV, this figure reaches 3.9%). Such characteristics were achieved by the scramjet of the accelerator aircraft, which did not have to drag the oxidizer into the stratosphere, and fluorine fuel of rocket stages, which had a specific impulse of 479 seconds in vacuum.


Despite the simultaneous start of the creation of the accelerator, the engines for it and the orbital ship, the engine was not ready for the project to be closed in the early 70s, the purges of the accelerator models continued until 1975, and only on April 25 of this year (after the official closing of the project) - the plane MiG-105.11 analogue was transferred from the manufacturer for testing. Since the ship had a military orientation, it was assumed that the cockpit would be fired, have their own engines and a parachute for the possibility of independent departure from orbit and landing on the ground. Due to common problems with the project, this part of the ship was never implemented.

The first MiG-105.11 analogue aircraft was dropped from the Tu-95KM in its 11th joint flight on October 27, 1977, after which the Groshevo runway landed. Tests of the analogue took place until September 13, 1978, when due to the flight director’s error when approaching at the wrong course in the evening, the pilot was blinded by the Sun, resulting in a hard landing that damaged the landing gear. On October 24, the aircraft was sent on the suspension of the same Tu-95KM to the Tushino Engineering Plant for repair. Although the analogue aircraft was later repaired, this flight at TMZ remained the last for the MiG-105.11. After the official closure of the project, there was still hope for using planes from other projects for launching the orbital ship; most of all, the T-4 project was suitable for this role



OKB Sukhoi, whose history is interesting in its own way. Since the USSR did not have the opportunity to create as many aircraft carrier groupings as the United States had, it was necessary to find some other way to deal with them. Conventional nuclear weapons were not suitable for these purposes, since during the time between obtaining information about the position of the aircraft carrier and the approach of the rocket, it could go out of the radius of destruction. Therefore, it was proposed for this purpose the creation of a small group of strategic bombers with nuclear missile weapons.

Calculations showed that to break through the air defense of an aircraft carrier connection they had to have a very high speed - of the order of 3M. Three design bureaus participated in the competition: Tupolev Design Bureau with the Tu-135 project, Yakovlev Design Bureau with the Yak-35 project and Sukhoi Design Bureau with the T-4 project. As a result, Sukhoi Design Bureau won the project, while Sukhoi and Tupolev quarreled, which led to their famous conversation when discussing the future of this project:

Tupolev: “Sukhoi is my student, I know him — he cannot handle the topic.”
Sukhoi: “It is because of this, Andrei Nikolaevich, that I am your student, I will deal with her.”

As a result, one instance of the T-4 was still built and tested up to the transition to supersonic, but due to the fact that Tupolev was able to ensure that the new T-4 samples were not produced at the Kazan Aviation Plant - a project in eventually braked and was soon closed. For further tests of the orbital ship, the MiG-105.12 (for testing at supersonic sound) was already manufactured and the construction of the MiG-105.13 (already for testing at hypersound) was started. Both of these analogs were not completed until the start of the Buran construction, when their construction was completely completed, while the third analog was still tested in a pressure chamber while the second simply stood on the TMZ until the late 70s. Now the only flying copy of the MiG-105.11 is in



The Central Air Force Museum in Monino, side by side with the T-4 and with the supersonic passenger Tu-144 (whose story was a little luckier).



Another very interesting point: Gagarin defended his diploma on February 17, 1968, the topic of his thesis was a spaceship with trellised rudders (as those now used on reusable versions of Falcon 9 family missiles ). In the future, this direction was to become the topic of his candidate work. Yuri Alekseevich died on March 27 of the same year in his final flight with an instructor, in which, after a long break in flights, he again had to obtain the right to fly independently ...


MAX



The project provides for a start from the AN-325 (an enlarged version of the AN-225 , built to transport the Buran, the central tank of the Energia launch vehicle and other oversized cargo weighing up to 250 tons of which it can carry inside the fuselage or on the external sling). The 275-ton construction, including a tank, an orbital ship and 7 tons of payload, was supposed to go into orbit thanks to a unique two-chamber RD-701 engineoperated on fuel components kerosene + hydrogen / oxygen. The engine had two modes: in the first of them, to increase traction, a significant proportion of kerosene was supplied to both chambers (which provided 2.5 times more traction), while later the engine switched to the second mode in which the supply of kerosene was completely stopped (providing 10 % greater specific impulse):
The project was widely known, but never received the proper funding. Despite its unique engine, the project inherits all the technical shortcomings of the subsonic carrier, and also has its own - it is a three-component tank in which it is necessary to provide thermal insulation of the three fuel components (hydrogen, oxygen, kerosene) that must be stored at different temperatures (about 20K, 50K and 300K, respectively). Much more promising in this regard (in my personal opinion, of course)it could be a complete abandonment of the carrier aircraft in favor of a ground launch, using drop tanks and preserving a one-stage circuit - this would solve the problem of thermal insulation with standard drainage systems (when the heated fuel components are dumped, and the tanks are powered by ground systems before launch) .

There were several European projects at once: RT-8



project of the German firm Junkers- provided for the launch of a two-stage cruise missile from a 3-kilometer cart with acceleration to 900 km / h; an air launch was also considered. Both stages assumed landing on the ground, the second stage involved the launch of a little less than 3 tons into orbit, and hydrogen / oxygen was also transferred from the first stage to the second stage. The project ended with the closure of the company in 1969.



The original project MUSTARD British aircraft manufacturer BAC- providing for the launch of three identical devices with a total weight of about 424 tons. After gaining 2 km / s speed and 56 km altitude, the engines were turned off, and the two outermost vehicles pumped the remaining hydrogen / oxygen fuel into the middle vehicle, after which they separated and landed on an airplane. The payload was supposed to reach 5 tons, the project did not go beyond the stage of initial design study, but gained considerable fame in the media.



The British project EAG.4396 provided for the launch of a ship and a missile stage from an airplane at a speed of 4M. The rocket stage had kerosene / oxygen and two drop tanks as fuel. The project worked out various versions of the ship / rocket as a carrier, but because of its military orientation, almost nothing is known about it.

The project “Le transporteur aerospatial” of the French company Dassault Aviation is an accelerator ramjet with ramjet ramp, booster stage and rocket plane in which hydrogen was to be used as fuel at all stages.

Modern projects

This is the Pegasus XL launch vehicle - it is launched at an altitude of 12.4 km from the Lockheed L-1011 Traistar modified wide-body passenger aircraft, an ultra-lightweight launch vehicle. The weight of the rocket is 23.12 tons, and the payload can reach 443 kg. Since 1990, only 43 missiles of this class were launched , while from mid-2013 Orbital ATK had only 2 contracts with NASA for which CYGNSS satellite was launched for $ 55 million on December 15, 2016, and ICON satellite should fly on December 8, 2017 already at a price of $ 56.3 million, after which the company does not have any contracts left. And this is not surprising: after the appearance on the SpaceX market launching tons of cargo for NASA at a price of around $ 87 million, the meaning of the use of "Pegasus" almost disappeared. And for commercial customers who cost $ 62 million to launch a Falcon 9 rocket, Pegasus looks like an even more ugly offer.

Launch of 8 microsatellites of 28.9 kg each for NASA’s CYGNSS hurricane tracking mission

Despite this, the company did not abandon its cruise missile and even signed in October 2016 an agreement on their launches from the world's largest Stratolaunch aircraft allowing to carry 3 " Pegasus "right away. But with the news about the first tests of the Electron rocket from Rocket Lab , the return to flights of the Japanese SS-520-4 rocket by the end of 2017, the first suborbital flights of the Vector-R rocket and the upcoming Firefly Alpha flights(having the same load class, but 6-10 times lower cost) - this project has almost no chances.



The project of the Swiss suborbital ship SOAR , using the achievements of another European Hermes project . It was assumed that the suborbital ship would launch an additional rocket stage (which the RSC Energia was supposed to produce under the agreement ), which would allow launching up to 250 kg into orbit. The first test flights were supposed to start in 2016, but due to financial problems, the company declared bankruptcy by the end of this year. The further fate of the project is in question.

SSTO projects can be classified as a separate category :

This is another promising branch of the development of means of launching into orbit called "single-stage-to-orbit" - a single step exit into orbit. The main problem with this approach is the need to gain 7.8 km / s of orbital speed and 200 km of altitude necessary for the reference orbit , while gravitational and aerodynamic losses lead to the fact that such a ship should have a reserve of characteristic speed of 9-10 km / s.

These are very harsh conditions for a ship with a liquid propellant rocket engine , since for the most efficient hydrogen / oxygen fuel pair that is currently used, it has a specific impulse of 3816 m / s at sea level and 4462 m / s in vacuum - according to the Tsiolkovsky formulait turns out that the ship in this situation should have a ratio of its own mass to the mass of fuel of about 1:10 or even more - that is, engines, tanks, control system and payload should have less than 10% of the mass. At the same time, the mass excellence of modern missiles using aluminum-lithium alloys and carbon fiber reaches 5%by weight only with kerosene / oxygen components, and in the case of hydrogen / oxygen fuel - this indicator is even less. That is, almost nothing remains on the payload. At the same time, the real possibility of implementing such a project appeared recently, with the first experiments on using carbon fiber as a structural material for the rocket itself and its tanks - the previous materials did not give a chance to obtain the necessary mass perfection.



X-30- The project of the reusable ship, worked out in 1982-1993. It was proposed to use a scramjet as an engine in the project, to cool the casing and recover energy - it was proposed to pump hydrogen under the casing, which, after heating, was to be ejected behind the ship creating additional traction. Alloys of titanium and aluminum and carbon-carbon composites (also used in Shuttles and Buran) were considered as cladding . The project was closed due to technical problems - in particular, the lack of existing models of scramjet engines, which were further developed and produced in projects X-43 and X-51 . The project "CROWN" from "GRTS Makeeva"



worked out from 1992 to 2012 is a single-stage launch vehicle with about 300 tons of weight, which, as the project progressed (and the transition from aluminum / magnesium alloys to carbon fiber), the payload grew from 1 to 7.5 tons of cargo. The project did not receive proper funding and was closed in 2013.



The British project HOTOL, launched in 1982, and its ideological successor, Skylonlaunched in 2004 and should lead to the first test flights in the area of ​​2025 - this is a reusable spacecraft project with hybrid hydrogen engines that should operate at a speed of 5.4 M and a height of 26 km, after which it will switch to using its own oxygen tanks . The ship should deliver up to 17 tons to the DOE and up to 7.3 tons to the GPO. The total project cost is estimated at $ 12 billion, according to plans, the ship should be used up to 200 times.

The Delta Clipper Project



Also referred to simply as DC-X, this project was the first attempt to demonstrate the viability of the SSTO idea “in the metal,” and the first rocket to land on a jet thrust on August 18, 1993 (thus becoming the basis for the Grasshopperfrom SpaceX). According to the program, 5 flights were carried out, the last of which ended in a hard landing, which damaged the rocket body. It was decided not to restore this test sample, but to make a new one (DC-XA) which, on its 3rd flight, could climb to a height of 3140 meters (4 times higher than Grasshopper flights), but landing after the next flight one of the supporting legs it didn’t come out due to which the rocket fell and caught fire (which was aggravated by a leak from the oxygen tank). Although the project costs at that time amounted to only $ 110 million (in terms of current prices), it was decided to abandon the project in favor of the following in the list:


Comparison of the sizes of the X-33, VentureStar and Shuttle

American VentureStar project- launched in 1992, it was very considerable in size as can be judged by the scheme: with a starting mass of one thousand tons, 20 of them should fall on the payload. According to the project, its smaller analogue, the X-33 , was to be built and tested , after which a full-size ship was to be built by 2004. Due to problems with the composite liquid hydrogen tank and other technical problems, the X-33 was never completed, which caused the cancellation of the entire project. In the future, NASA managed to solve the problem with composite tanks and a number of other problems - but it was already too late. Based on the achievements of these projects, the XS-1 project is being developed under the auspices of DARPA :



PSIf you were interested in the topic of air launch - I would recommend the book “Cosmic Wings” V.P. Lukashevich and I. B. Afanasyev, where the theme of pre-existing projects (like the X-15 and Spiral and many others) is covered in much more detail.