Rocket sled is proposed to be used launching space rockets. They are in some degree positioned upwards, or horisontal (Hotol). Why not uising rocked sled positioned straight upwards? Now are many private space firms that are developing lightweight space rockets as cheap as possible. Rocket must be as light and efficient as possible. Rockets are launched upwards. Lightweight space rocket can use 100 - 200 m vertical rocket sled, which is in fact lengthened launch tower. Lightest space rocket is “Blue Whale”, 1,7 tons, and many lightweight rockets, including one stage to space (Haas rocket etc.) are being made. Light rocket can be “shoot” upwards using solid rocket booster that is attached to launch tower with sled system, space rocket and booster does not need any explosive bolts etc. connection, the space rocket simply rests against booster and booster pushes it upwards. Near top of launch tower booster has used all fuel and braking mechanism slows down empty booster casing, space rocket continues to upwards. Now rocket has gained speed and acceleration when it leaves launch tower / vertical rocked sled, only then rocket starts its own engines. Very heavy rockets accelerate slowly, Saturn 5 and SpaceX BFR. Even super heavy rocket like BFR can have large solid booster that pushes BFR to fast acceleration until launch tower ends. BFR has then high acceleration speed when it leaves launch tower, and it starts its own engines only then. When empty booster case reaches launch tower top it is braked to zero speed and it drops back to launch pad, braking slows down it before it drops at launch pad, and solid booster is ready to be reloaded and used again.
One booster can be used to boost launch speed of several type of rockets, all rockets that use that launch pad. Simplest solution is system where normal launch tower is used, its not lengthened, booster is just added below rocket and sled / braking system in launch tower. Minimal amount of modifications is needed in launch site. Light rockets can use long 100 - 200 m long launch tower that is used as rocket sled and launch tower.
Light rockets also can use cheap boosters, like JATO / RATO (rocket assisted takeoff) “bottles”. Aircraft do not use them as often as 1960s, but some (Hercules) do, and JATO is used now to launch some unmanned aerial vehicles. Commercial JATO rockets that has about 15 second burning time can be used. They can even be recovered after use if small parachute is if included in them, and reused, if it is cheaper that way. JATO rockets can be “first stage” of some light space rocket, only when they are burned rocket s own main engine start. Rocket with JATO is launched straight upwards, not in some angle like airplane with JATO.
Other cheap solid boosters can be used with new commercial light space rockets. India used SLV, ASLV rockets and then used them as boosters in PSLV rockets, 9 and 12 tons weight. They should be reasonably cheap, so can be used to boost performance of modern light commercial rocket. The “New space” movement has many new private rocket firms that need as cheap space rocket tech as possible.
Whole rocket could be “outsourced” to some cheap country that has rocket manufacturing, only design office is in USA or europe. So in India, China, Pakistan etc. can have “OEM space rocket factory” that makes space rockets according to orders from europe or USA, and only money and is needed if someone wants to make space rocket. Even design of rocket can be outsourced, so someone orders space rocket, gives specs to manufacturer, and manufacturer designs and makes space rocket according those specs, in India, China or Pakistan.
According to some information SpaceX Falcon 9 rocket reused version really costs only about 40% of its selling price. SpaceX has stated that if maximum turnaround time (about 10 days) between launches is used reused Falcon 9 has 5-6 million dollar cost to SpaceX, but selling price must be higher because of design costs, profit etc. Space shuttle never reached “break even” point when it could have been commercial success, 56 flights per shuttle was proposed in each year, and it would have become cheap “aerospaceplane”. But president Reagan signed law 1984 that ended shuttle monopoly in space launches, and made shuttle commercial failure then.
In order to make space rocket as cheap possible, as many as possible launches are needed. It is possible that rocket manufacturer itself invest profit from rocket launches to increase launch schedule. Rocket manufacturer itself can finance cheap scientific satellites or other satellites and launch them, when maximum turnaround time is reached and price of rocket is at its cheapest, rocket manufacturer does not need itself to finance rockets anymore because price is now so low that commercial customers can order cheap rockets as fast as manufacturer can launch them.
Cheap standard series produced scientific satellites, that are offered to universities etc. can be used to gain as many as possible rocket launches. Astronomical satellites etc. Falcon 9 can have 5 m mirror astronomical satellites series produced, 10 - 100 unit series production. BFR can have monolithic 8,4 m beryllium mirror space telescopes, infrared, visible optical, near ultraviolet (LUVOIR) launched to Lagrange point or near earth orbit. Serial production cuts down costs, both telescope and rocket. From Hubble, Herschel and Webb telescopes, their sensors can be used, not just in one space telescope but in many dozen. Smaller space telescopes with 30 - 50 cm mirror can be manufactured and launched cheaply, those smaller astronomical telescopes can be marketed and sold to private persons, they are manufactured in series production of hundreds of units, and are cheap enough that they can be bought just like normal astronomical telescopes of 30 - 50 cm size are sold on earth. So amateur astronomers can buy space telescope of 30 - 50 cm size and are not restricted to use same size telescopes on the ground of earth. Other scientific standardised satellites can be sold and launched to space, some part of their cost is “sponsor paid” by rocket manufacturer that tries to make launch costs as small as possible launching rockets as fast as possible. When this point is reached and price of rocket is at its cheapest rocket manufacturer does not need to “sponsor” launched satellites no more.
Fast aircraft like Mig 31 and F15 are used to launch anti satellite weapons. For some reason commercial satellite launches using same principle is not used. Fast air launch in high altitude would make really economical rocket launch. Mig 31, Mig 41, F15 , F22, Eurofighter Typhoon etc. can be used. Not just solid rockets but liquid rockets, hydrogen / LOX can be used. When those aircraft launch space rockets they seem to be normal fighter versions, but special launcher version can be made, simple modifications, all equipment that is not needed is needed, radar etc, and aircraft is lightened like those fighters that are used to world speed and height records. Fuel can restricted to minimal amount that is just enough to rise to altitude and then plane glides back to earth and just before landing starts its engines again, and with minimal safety reserves. Saved weight of fuel etc. is used to make external load heavier, and one or several underfuselage hardpoints are used to transport one heavy space rocket. Underfuselage hardpoint(s) are hardened to maximum load, structural strengthening of airframe is perhaps needed. Aircrafts modified that way can carry space rockets that can offer really cheap space launch, with reasonable payload. For some reason this has not been made, only military weapons are launched to space using this fast fighter aircraft to altitude launch principle. Heavier aircraft can be used, british (Bristol) “Space cab” launcher concept has specs that are close to Tupolev Tu 160 aircraft. Space cab has additional rocket motor that increases speed from mach 2 to mach 4. Perhaps Tu 160 can be modified for additional rocket use, and air intakes of engines closed when over mach 2 speed is reached, front fuselage modified to mach 4 speed etc.
Space tourism uses in some plans airplanes / rockets that rise to upper atmosphere 60 - 100 km high. Mig 31 or F15 fighter can be modified to “tourist plane”, one pilot in plane nose and then seats for 4 - 6 passangers. Most of jet fuel weight and external weight that normally is in hardpoints is used to rocket fuel, and plane has additional rocket motor (and normal jet engines). When jet engine max altitude is reached rocket motor starts and launches plane to parabolic flight path. If plane reaches very high altitude perhaps some sort of heat protection is needed when plane glides down to atmosphere, or such gliding path is used that it generates less heat. Air intakes are closed when speed is near mach 3 or over. Air intakes can have doors that expand air intake area in high altitude 2-3 times larger than near ground, so jet engines get more thin air, and when rocket engine starts air intakes are closed.
Balloon launch of rockets can lift light rockets economically. If balloon uses hydrogen, when balloon is its maximum altitude and ready to explode because of gas pressure, hydrogen can be transferred using flexible tube to rocket engine that balloon is carrying, during few seconds when rocket starts it uses gaseous hydrogen as propellant (otherwise it uses liquid hydrogen), in rocket chamber and in rocket nozzle also where gaseous hydrogen is used as sort of “afterburner”. After few seconds tube separates from rocket and and rocket goes with its own power to space, but in few seconds large amount of gaseous hydrogen from lifting balloon is used as rocket propellant, both in rocket chamber and rocket nozzle.
There are other topics in Robin Hood Coop forums that are near this subject, “High explosives as rocket propulsion”, “Useful way to use hydrogen in space station”, “Cheap astronomical telescopes”.
The additional solid booster that is used as vertical rocket sled in previous post, it does not need brakes in top of launch tower because hot gases from exhaust nozzles of rocket proper stop sled booster and push it downwards, only near launch pad braking is needed when booster drops back so landing is relatively soft. But this additional sled-booster is not efficient, 50 m/s (5 g) acceleration in 400 m high launch tower with rocked sled booster is just 200 m/s, rocket needs 7000 m/s in low earth orbit and about 1000 m/s more for “delta v” atmospheric drag etc. So only 2,5% addition, so if BFR rocket uses this and has 180 ton payload to low earth orbit it is just 4,5 ton more. If light rocket has 70 m/s (7 g) sled booster and 450 m high tower (launch tower can be like TV mast, slim and high and it has cables anchored to ground that keeps it up), it is still only 250 m/s so only about 1/30th increase of efficiency, so if rocket has 300 kg payload it is only 10 kg more, 310 kg. So less useful method. Electromagnetic catapult can be used with light rockets like used in ships with airplanes. But kilometres long rocket sled or catapult in mountainside is much better idea.
But then another idea: additional liquid, that is not fuel, is pumped to rocket when it rises, it is not pumped to rocket engine, but to nozzle. It is something that does not burn (easily), water?, or boron?, or something. It is only additive to hot exhaust gases, and makes them more faster, more dense etc., something that increases specific impulse (or maybe it has chemical reaction with exhaust gases). So gas flow from exhaust nozzle is combination of rocket engine hot gases and this additional pumped from ground liquid that turns to gas / or reacts with rocket gases and makes some other energetic compound. Most safe is option is just some liquid that increases specific impulse and does not make dangerous (explosive or burning) reaction products with hot rocket nozzle gases. Pumps are in launch tower top, launch tower is 200 m high, and from there it is pumped up to 600 m higher, so combined height is 800 m, only then liquid tubes that are flexible tube material, disconnect. Big rockets accelerate slowly, like Saturn 5, so when rocket reaches 800 m it has received plenty of this specific impulse increasing liquid.
About high speed airplanes: jet fighter airplanes can be modified for satellite rocket carrying duties. They can have strengthtened underbelly hardpoint(s), internal fuel is minimum because plane only needs to flight to altitude and glide back to airfield, only near airfield jet engines are used again. Underwing hardpoints can have additional jet engines that are from surplus old mach 2 military jets, those engines are used in full power only in high altitude, to increase flight ceiling, but those engines takes payload weight from space rocket. In ground jet fighter can use JATO in takeoff, JATO is supported in ground metal stand when connected to plane so no weight to plane, and when JATO is fired it is projected so that it has slightly lift upwards, so it does not bring extra weight to plane but upward lifting force. Also old military surplus naval catapult or electromagnetic catapult can be used in airfield to give plane speed in takeoff. It is possible to have 15 ton (or more) load (space rocket) in fast jet fighter that is stripped off / in minimal jet fuel? Space rocket can be liquid hydrogen / oxygen powered, steaming hydrogen from rocket fuel tank can be directed to jet fighter afterburner and used as “jet fuel”. Engines of plane can be changed to more powerful, for example F 22 that has two F 35 engines, and mach 2 + capacity. Wing area can be increased, wingtips extended, air intakes increased, max load increased etc.
The tourist plane version that is used to lift space tourists to 60 - 80 km height needs rocket engine in plane together with jet engines, if rocket motor uses RP1 and jet engine JP10 same fuel tanks are suitable for both, only liquid oxygen tanks are needed or other oxidizer. Like in space rocket carrying aircraft, all that can be taken off from plane is taken away , radar etc, so pilot sits in radar compartment and behind him is 4-8 passengers, sitting in pairs, where previously was cockpit. Some heat shielding perhaps is also needed, and doors that close air intakes in over mach 3 speeds. But using jet fighter is simpler and faster than make space “tourist plane” from scratch. South Korea is making its Yun Feng ramjet missile to a space rocket version. Such ramjets / scramjets (missiles) can be turned to space rockets for civilian use. Jet fighter can carry ramjet/scramjet rocket, and this is second stage of space launch system (first is jet aircraft), third stage is liquid fuelled (or solid fuelled) rocket that carries the satellite payload. This rocket is connected to ramjet/scramjet vehicle, and this to airplane. Three vehicles of this launch system (jet aircraft, ramjet/scramjet, and rocket) can be used like rocket stages.
Light privately made space rockets need all extra power they can have, so if they have access to russian Syntin fuel they can increase payload, russians used it only in upper stages, but small rockets can use it in all stages. Syntin was expensive for russians, their low kerosene prices, but westeners perhaps have money to buy Syntin. Also tripropellant engine has more specific impulse than bipropellant LOX/RP1. If only small amount of hydrogen is needed to increase specific impulse of LOX/RP1 engine, then LOX/RP1 stage can have tube to upper hydrogen/LOX stage, and through this tube comes hydrogen to tripropellant rocket engine. So second stage has used some of its hydrogen when it separates from first stage, but this is one way to increase specific impulse. “Ecosene” is new rocket fuel made from plastic waste. And “Synthesis of strained high-energy rocket bio-kerosene”. Also cheap additional solid boosters are available (perhaps) for private firms that develop light and cheap space rockets. Those are not so small, indian additional boosters connected to rocket sides are 9 and 12 weighting, from China and other countries perhaps is available cheap and small boosters that can be connected in sides of small 50 - 100 ton rocket.
Big rocket manufacturers can increase their rocket manufacturing if they direct some of their profit from making rockets to sponsoring space satellite programs. Sponsor money does not go to cheaper rocket prices, but for scientific satellite programs, rocket maker can offer cheap series manufactured satellite bus, and for example series manufactured space telescope, with satellite bus and mirror blank, but buyer must arrange mirror polishing and also buyer must have sensors, cameras, electronics etc. for that space telescope. Space telescopes can be different sizes, 12 m fits inside enlarged BFR rocket fairing or 15 m if mirror is sideways and fairing extra wide like some russian rocket fairing that has wide satellite dish inside. Telescope is then short focal length like Herschel space telescope. Large but light single piece (monolithic) mirrors can be made from beryllium etc, although biggest mirror making machinery is 8,4 m nowadays. From 15 m can be go down to small 30 - 50 cm space telescopes that are sold as complete “package” to amateur astronomers and launched like cubesats to space most economical way. When rocket manufacturer offers series manufactured (cheaper than unique designed / manufacured things) standard parts to scientific community, and also sponsors science offering some seed money to those who buy these scientific satellites, rocket manufacturer gets more rocket orders, and in the end rocket mass manufacturing is in its most cheapest. Then when rocket manufacturing has reached its saturated phase and rockets cannot be made any cheaper, rocket manufacturer can keep all profit and not direct part of it to scientific community (seed money, sponsor money), because rockets are now at optimal low price range and their series manufacturing is in full swing. Reused Falcon 9 rocket has minimum turnaround time of 10 days, and several rockets can be used. With 10 rockets rocket can be launched every day. Price is 5-6 million dollar for Falcon 9 plus profit.