Ability to reuse the rocket allows to cut launch cost significantly. At the same time, it is preferred to lower the expenses and related rocket modification, due to the fact that its primary goal is to deploy the payload to space. As the result of the research in the direction indicated, here is the following solution.
The complex consists of a ground or sea based landing site. The dimensions should be big enough in order to get the rocket (1), taking in consideration landing accuracy estimation.
Landing platform deck (2) designed to withstand the weight of the landing rocket (1) and has a cellular structure at the base for passing the jet stream.
There is a system of diversion and quenching the reactive stream of the descending rocket (1), located right under the deck (2). In the elementary case, it could be a water pool.
There are four support towers (3) located on the square perimeter. (The number of towers (3) could be different; however, four- seems to be the optimal). Holding ropes (4) are coming out from the tower and moving back and forth in the manner to form the single level capturing loop (6).
In case of using multi-leveled (5) construction of the capturing loops, there is an opportunity to suspend the rocket (1) by the loops net. In this case, the requirements for the landing site and rocket (1) design changes are minimal.
In general, the construction functions as following: Initially on the landing site, which is ready to accept the rocket (1), the capturing loop are wide open, so it forms the perimeter of capturing area.
When location of the landing coordinate becomes clear enough, the second phase starts. Positioning and forming the capturing loop (6) around the descending rocket (1).
Automated system monitors the positioning of the capturing loop around the rocket (1), and by means of winches (7), gradually narrows the capturing loop, yet, avoiding the contact with the rocket (1) hull before the touchdown. However, the loop can sometimes be used to stabilize the position of the rocket (1) during landing.
During the rocket’s touchdown, the final tightening loop (6) occurs. Thus, it ensures a secure fit of the rocket (1) at vertical position.
In the above single level loop version, the construction is only able to withhold the rocket in vertical position.
By increasing the number of the capturing loop (6) levels, it can reach capability to capture rocket and hold in suspension in the net.
Hereafter is an example of the triple leveled capturing loop used on the sea based landing platform (8). Hold the rocket (1) in suspension in the net allows to eliminate the platform deck.
That was a general scheme of the system operating. Now it is necessary to consider important devices and system components.
In case of the rocket (1) stands on the landing platform and the net of loop carry out only vertical position withholding function, the rocket (1) must be modified as following. For instance, the support ring (9) or other type of rigid framing shall be installed at the bottom base of the rocket (1) as shown on the picture. At vertical standing, the weight load of the rocket (1) transmits through the rods (10) to the support ring (9), protecting the jet nozzles (11) from damage.
With the single-level loop (5), the rocket hull require light reinforcement in the area of the contact with a capturing loop. Since the force for maintaining the rocket in a vertical position, are extremely small.
With the multi-level loop (5), the load on the rocket hull is further spread vertically and as result no need any rocket change.
When the rocket (1) is captured and held in suspension in the net of the multilevel capturing loop (5), it’s eliminates the support ring (9), but requires reinforcement of the rocket hull, especially it lower area. The cables tension control system is adjusted so that the rocket weight load fell on the lower levels of the multilevel capturing loop and upper levels are only used to stabilize the vertical position. Such tension distribution is optimal for towers (3) too.
It is obvious that it’s better if the loop gripping force location coincides with location of the rocket hull frame bulkhead (if it exists).
Kinematics of the capturing loop explained in the following simplified scheme. In fact, the single level loop consists of four independent loops that being pulled respectively toward the support towers (3).
Here is an image of one of the loops (12). Other three are hidden from view.
Loosely spinning wheels (13) of two blocks, and the auxiliary tensioner (14), allows forming the loop (12) with the maximum inner area. The main load (15) from the loop, after rocket (1) captured, will be transmitted to the rightmost support tower (3).
Here we unhide more. Add two blocks wheels (13), tensioner (14), and the loop itself. The main load (15) from the loop, after rocket (1) captured, will be transmitted to the opposite leftmost support tower (3).
On that scheme, we show only two other loops working in the perpendicular directions.
The full scheme looks as following
In reality, the block (16) and the ropes might look as pictured.
Block (16) closer.
Block spinning wheels (13). Only one rope to the block joint(fixation) place (17)
Pipes (18) of soft, flexible material could be used to give a gentle interaction of the capturing loop ropes and the hull of the rocket (1). The length of each pipe shall be equal to quarter of the rocket (1) hull circle or a bit shorter. This will allow distribution holding force of the capturing loop more evenly. Moreover, due to the rotation of pipes, it will allow vertical sliding of the loop on the hall, improving the positioning of the narrowing loop around the rocket (1) hull.
In the case of the single level loop, the tension for the ropes goes through blocks (19) (20), located on the top of each support tower.
For multi-leveled version, lower level’s ropes have their own tension blocks located along the support tower on the height of each loops respectively.
Required tension carried out by means of a winches (7), located at the towers (3) basement.
After rocket’s capturing and fixing phase, further withholding ropes tension carried out by trivial winch lock.
Highlight advantages of offered solution.
- All the complexity and structural modifications associated with the landing of the rocket, transferred from the rocket to the landing site. Consequently,it minimizes construction modification of the rocket and keep its former weight and reliability.
- System of the ropes allows firmly fix the rocket at any point of quite big landing pad
- Loop form of holding contact allows distributing load along the circle of the hull evenly and helps to avoid pin load. In case of multi-level loops scheme, the load additionally spreads along the height of rocket.
- Absent any load on ropes at the phase of loop positioning loosely around descending rocket,allows the following:
- To positioning fast and precise, which is important with unpredictable circumstances like stormy weather with strong gusty wind or in case of instability at sea rolling on sea based platform.
- To use high-speed winch of simple construction.
- When used in sea-based barge eliminates the need for additional means of fixing.
- Joint, coordinated and synchronized work of the rocket on board positioning systems and loop positioning system, at the landing site will significantly increase the reliability of withholding the rocket, even the most difficult conditions.
- At present time the level of development of jet technology does not allow to change the thrust magnitude dynamically and in a wide range. This is not necessary for liftoff phase, but become critical for soft landing.
During the landing, especially in its last phase before the touch down, changing the direction of the thrust used as the primary means to prevent from tilting and keep the rocket upright. Therefore, it is important to have thrust strong enough until the rocket fully touch the pad. If landing pad is kind of an even solid surface, on the minimal (few meters) altitude the vertical force of the thrust increases drastically due the “Ground effect”. At the same time, efficiency of transversal correction increases not significantly, however its characteristics are changing a lot. To compensate the influence of “Ground effect” it is required to decrease thrust magnitude. Which does badly affect the ability of transversal stabilization. Decreasing of thrust magnitude is possible in the quite narrow range and down to particular minimal level at which the engine shuts down. Then the thrust drops to zero. A construction of several engines were utilized to widen the range of thrust magnitude. It allows to decrease the thrust magnitude gradually by shutting down of the engines one by one.
Minimization of the “Ground effect” influence would allow to enhance the controllability at very last, crucial moments before the touchdown.
The solution offered is to use a landing pad with a cellular structure or eliminate landing pad at all by grasp hold the rocket hanging in the multi-level net. Obviously, that final capture position of the rocket should be high enough to avoid negative impact of the ground down below. Water pool located under the descent rocket could be a good help for cooling jet stream, decreasing its volume, therefore suppressing the impact of “Ground effect”.
I hope this patent will take its place next to the US8678321.
© Chikirev Sergey