LAS - Launch Assist System

The companies involved in the space business are making efforts to reduce the launch cost, and their efforts are directed mainly to improve technologies that are decades old.They push the envelope to gain a few more seconds of specific impulse by increasing the chamber pressure, or using slightly better propellants like methane instead of kerosene, or to densify the propellants by cooling them.
ARCA made similar efforts by creating a single stage rocket supported by an innovative aerospike engine.
The reusability, another trend in today’s rocket development, did not deliver the trumped cost reduction of orbital launches yet, and the prices remain high. Why is this? Because after each flight the vehicles need extensive checking and refurbishing leading to long turnaround time.
Apparently, no effort was enough to make spaceflight significantly affordable. For us it was clear that all these efforts were doing nothing more than to improve the performance of decades old technologies. In addition, with each new improvement, sometimes the overall cost is becoming even higher.
In the case of current technology, “making it better” was leading to increased complexity, hence higher cost. It was clear that small steps towards innovation were not the answer to spaceflight cost reduction, and the answer-needed will come from a radically different approach.
Therefore, we started by asking ourselves four fundamental questions:




1. Why are rocket launches expensive?
Rocket launches are expensive because the vehicles themselves and the fabrication and launch operations are complex. Complexity leads to high costs.

2. Why are rocket systems complex?
Because their propellants are volatile, explosive, corrosive, toxic, carcinogenic, polluting, cryogenic, exhibit high burning temperatures and pressures in the engine. All these characteristics are leading to the necessity to have complex machinery, fabrication processes and operations, extreme safety measures, in order to be able to handle the extreme propellants parameters.

3. How can we avoid rocket’s complexity?
Since we identified the propellants as the root cause of rockets high cost, it was clear for us that incremental evolutions are definitely not helping towards the creation of a truly cost-effective rocket system. We knew that some radical changes were needed to get a significant cost reduction and these meant only one thing: eliminate, or at least significantly reduce the use of volatile, explosive, corrosive, toxic, carcinogenic, polluting, cryogenic propellants.

4. What potential propellant has completely different properties than the current ones?
As much as it might seem a very bold approach, we looked at the cheapest, cleanest and easily available liquid: water, and we looked at ways to work with it. And after thousands of hours we spent on the topic, analyzing various options, we concluded that the only option that has a potential at this point is an electro rocket in which the water is heated and produces thrust from evaporation accelerating the water vapor in a convergent-divergent nozzle.
Therefore, we identified the root cause of rocket launches high cost: the propellants. They are not generating high costs by themselves, but by their nature and associated measures of complex fabrication and operations. Water completely avoids these.

On top of everything, water as propellant does not lead only to an unprecedentedly cost effective vehicle to build and launch, but it came with two other great features: no pollution and unprecedented safety.



Extensive tests were done at ARCA since July 2018 to develop a water-based rocket engine, and here is how the system works:
The rocket tank is filled with regular water mixed with benign phase destabilizers, used in the food industry. The water from the tank is electrically heated to temperatures of hundreds of degrees in a process that lasts for hours.Then the water is injected into the engine where a phase change occurs from liquid to vapors. In the engine, a further heating occurs. A second electric heating phase takes place in the engine using high discharge LiPo batteries, the same type of batteries used by ARCA to power the cutting-edge ArcaBoard.
Even for our team an inherent question arose: how can we use a rocket that offers only around 50 - 60 seconds of specific impulse? Because this by itself can’t give the necessary performance for an orbital flight, and not even for a suborbital flight. We were literally struggling to find an option to work with a rocket with such low performance. Because when you look at current rockets and see specific impulses that are around four times higher, the first instinctual reaction is to quit the idea thinking: this isn’t going to work. But the tremendous advantages offered by the water in terms of cost, safety and lack of pollution was what kept us pushing and come back to it over and over again, to find an option to work with this system.
But then we looked at the Space Shuttle and Ariane 5’s SRBs that are indeed low performance rockets by themselves compared with the vehicle’s main engines from the core stages.
Their impulse is lower than their main engines and the propellant mass to empty mass ratio is very low, but the thrust to weight ratio is very high, as we can see from the below table:



It was clear that what matters for boosters is the thrust/weight ratio, while the specific impulse is of secondary importance. As long as the thrust to weight ratio is higher than the first stages’, the booster will fulfill its duty to contribute to the vehicle’s acceleration during ascent, regardless of the booster’s impulse. Also, the higher the acceleration at start, the better the flight performance of the orbital vehicle and LAS was designed with this feature in mind.
With this conclusion well structured, the team started to perform simulations to see what is the impact of the use of a water booster having a low impulse on orbital vehicle’s performance.
We named it the Launch Assist System (LAS).
At impulses in the range of 50-60 sec, the engine’s performance is lower compared with the ones using classic propellants, but we found it ideal from many points of view to assist the launch of current rockets.
The Launch Assist System (LAS) is a lifting vehicle, designed to boost the orbital vehicle’s performance, using hot water as propellant, safe and clean, allowing a major cost reduction of orbital launches. Built in the corresponding size for the lifted payload, it can transport any orbital rocket to altitudes of around 3,000m and speeds of around Mach 2.

It was concluded that LAS can be used both as booster as well as a first stage for an orbital rocket, providing a boost of their payload weight with up to 30%, or make the current rockets use 25% less polluting propellant.

For more details about the Launch Assist System, check the: White Paper.











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