The starship ship is sure to offer a high test flight next week

Starship – An unmanned flight test of the Starship prototype is currently being prepared in Boca Chicago, Texas. The target altitude of 15 km is 100 times higher than the test flights of the model series to date.

SpaceX has tested the ship’s engines several times. The flight is scheduled to be tried next week. The exact schedule is not yet clear, but the test may start as early as Monday.

“The goal is to test the three take-off engines, the wings, and the transition from the main tank to the additional tanks and the turn of the landing,” Elon Musk commented on Twitter.

The SN8 prototype is the same size as the final one, i.e. 50 meters long and 9 meters in diameter. However, it is much lighter than the final vessel and does not have additional engines designed for vacuum conditions.

The wildest part of the unmanned flight test is that after completing its legal altitude, the ship is supposed to turn to its “stomach” to maximize air braking. This can be compared to a parachutist who spreads his limbs horizontally in a drop.

During the landing, Spaceship controls its position with its wings. The aim is to slow down as quickly as possible so that landings with rocket engines over the last two kilometers consume as little propellant as possible.

The stages of the test flight are presented, for example, in an animation created by the enthusiast. As you know, SpaceX is going to show the flight live on YouTube.

“A lot of things have to go right, so we have perhaps a 1/3 chance (to land successfully),” Musk estimates.

The biggest risks relate to the durability of Starship’s pressurized tank structures during flight operations and the success of the turn.

Even when ready, Starship will not be able to ascend itself into orbit, but will need a lower large rocket phase, Super Heavy. Both rocket phases are designed to be completely reusable and are sized to allow Mars travel for 100 people.

5 Facts About the SpaceX Starship That Set It Apart from Other Rockets

Starship

The SpaceX Starship, once operational, will become the most powerful super heavy lift vehicle to ever exist. Outclassing the capacity of even the mighty Saturn V, Starship will deliver dramatically more payload to space for only a fraction of the cost of competing rockets. Here are five facts about Starship that set it apart from other rocket vehicles.

1. It Features Raptors

The rocket engine that will loft Starship into orbit is the SpaceX’s Raptor engine. A feat of engineering on its own, the Raptor recently set a rocketry record by achieving the highest combustion chamber pressure ever of 330 bar which produces over half a million pounds of force. The Raptor is also the only engine in existence to use the full flow staged combustion cycle for power, a historically hard process to implement.

When compared to other rocket engines such as the F-1 that powered the Saturn V, or the RS-25 that powered the Space Shuttle and its SpaceX cousin the Merlin, it seems that the Raptor falls short. Only producing about a third of the force of the F-1, around half the thrust to weight ratio of the Merlin, with less specific impulse than the RS-25, its metrics seem to indicate that the Raptor isn’t the best choice to fly to space. However, there is one single metric, possibly the most important metric, which blows all of the Raptor’s competition out of the water: cost. The F-1 costs about $30 million per unit. The RS-25 costs around $50 million. The RD-180 Russian workhorse costs $25 million. The next closest from a competing company is the Blue Origin BE-4, which costs $8 million per unit. The SpaceX Merlin actually costs less than the Raptor at $1 million per unit compared to the Raptor’s $2 million per unit. But once you account for the cost per kilogram lifted to space per intended flight, the Raptor does the best at a 5x cost advantage over the Merlin over the course of its lifetime.

This is the true power of the Raptors. When you take all the engineering hurdles overcome, all the optimizations implemented, and all the decisions made, you end up with the most cost-efficient rocket engine in history. It is intended for Starship to have six Raptors mounted on it, three for sea-level use and three for vacuum use, while 28 are to be mounted on the Super Heavy booster which will carry Starship into space.

2. It Uses Methane

While on the subject of the engine, another noteworthy fact is that the Raptors use methane as their primary fuel source. Historically, the two rocket fuels of choice are kerosene (also known as RP-1) and hydrogen. For example, the Saturn V used kerosene, and the Space Shuttle used hydrogen. Without going too far into the details, the main reasons for these choices over other fuels come down to energy and storage.

Hydrogen, when burned with oxygen releases a lot of energy. In fact, it is nearly impossible to find a more energetic fuel suitable for high-velocity rocket exhaust than hydrogen. So why not use hydrogen? Well, it’s not easy to store. Hydrogen, with its high vapor pressure, tends to boil quickly. This becomes a problem when your liquid hydrogen tank warms up inside the rocket while it’s sitting on the launch pad waiting to go. It’s also unsuitable for long-term storage due to hydrogen’s tendency to cause hydrogen embrittlement in metal storage tanks, like the ones being used on Starship, reducing the strength of the metal over time.

On the other side of things is kerosene. The type used in rockets is a highly refined grade of kerosene called RP-1. Very popular in launch vehicles, especially for the main booster stage, kerosene has none of the storage problems hydrogen has. RP-1 can happily sit in a liquid state on the launch pad for hours and not cause any problems. So why not use kerosene? While not quite as energetic as hydrogen, the real issue when using kerosene is the coking problem. When kerosene is burned it releases unwanted byproducts, mainly soot. This soot tends to clog engines over time, making reuse of engine components without refurbishment a nightmare. The Raptors specifically are aiming to be as reusable as possible.

So that leaves methane the seeming rocket fuel choice of the future, as it’s used by two next-generation rocket engines, the Raptor and the Blue Origin BE-4. Liquid methane sits in the middle of other rocket fuels. Not as energetic as hydrogen, it can be stored long term in metal containers. It’s not as easy to handle as kerosene, but it’s much more energetic without having the coking problem. As an added bonus, methane can be made on the surface of Mars relatively easily, which kerosene can’t. All the above makes methane the ideal choice for a rocket vehicle designed to launch to and from the Red Planet.

3. Starship – It’s Made Out of Steel

When deciding what to construct the body of a rocket out of, a great many materials are quickly eliminated. Whatever material you end up going with has to have many desirable properties. It has to be strong enough to support the weight of the rocket payload, propellant, and body, while also being light enough to not be a significant weight contribution. It must be able to handle the massive temperature swings of storing incredibly cold cryogenic fuel while also maintaining integrity during the extremely high temperatures experienced during reentry. Lastly, you want your material to be as cheap as possible.

The majority of rockets use either aluminum or titanium for their main body, with some additional parts being made out of carbon composites. Starship is being made out of steel, specifically a combination of 301 and 304L stainless steel. Titanium and aluminum, both being light and strong metals, tend to fail around 300-400 °F, while steel can tolerate closer to 1500-1600 °F.  Steel also tends to become stronger when dealing with low cryogenic temperatures, something the other two do not.

Carbon composites may be promising in the future as they are very lightweight yet strong materials. Unfortunately, they’re expensive when compared to steel. According to Elon Musk, SpaceX was spending close to $200 per kilogram of carbon fiber compared to the $3 per kilogram they are now paying for steel. This switch to steel has allowed SpaceX to prototype and iterate at a rapid pace that they wouldn’t have been able to do if they were still using carbon composites.

4. It Can Land

Of course much of the above wouldn’t matter if Starship was incapable of landing back on Earth after a flight. Landing and reuse is central to the SpaceX strategy. Musk often likes to compare modern rockets to commercial airliners. He likes to point out that our current rocket paradigm of discarding the rocket after use is akin to throwing away the airplane after a single flight. In that light, it seems obvious why rockets have been so historically expensive.

Landing a rocket is not easy, to say the least. To date, the only other orbital rocket to have landed successfully is the SpaceX Falcon 9. The Starship landing will be much more challenging than the Falcon 9 landing. For starters, the Falcon 9 does not land the whole rocket stack. Only the booster lands, and sometimes the fairings are caught, constituting around 70% of the rocket recovered. Starship, on the other hand, will not only need to land itself, but the Super Heavy booster stage will need to land as well, constituting 100% of the vehicle.

Starship will also have to deal with dramatically higher velocities than the Falcon 9 booster. Once the upper stage of the Falcon 9 separates, the booster is only on a relatively slower suborbital trajectory and does not need to shed as much velocity to get down to the ground. Starship, on the other hand, will have to shed all the velocity it picks up on its way back from Mars. Musk estimates that at minimum, two aerobraking flybys in Earth’s upper atmosphere will be necessary to slow Starship down before it can land.

Lastly, the landing procedure itself is much different than the Falcon 9 booster. Whereas the Falcon 9 comes down in a vertical orientation the entire time, Starship will have to perform a belly flop maneuver. Starship will orient itself horizontally to the ground when descending in order to make use of its actuating fins for steering through the air. Then at the last moment, it will flip itself around vertically again in order to deploy its landing legs and touch down on the ground, a much more complicated and dangerous maneuver compared to the Falcon 9.

5. It Will Be Able to Refuel in Space

Science-fiction author Robert Heinlein once said in an interview that “If you can get your ship into orbit, you’re halfway to anywhere.” It turns out that roughly half of all the energy expended traveling to anywhere in the solar system, be it the Moon, Mars, or even the outer planets, is spent just getting into the orbit of Earth. The problem is that for every kilogram of payload you have, you also need the fuel to lift it into orbit, but then that fuel also needs additional fuel to lift the first amount. Eventually, the math works out to be that you need an absurdly large rocket to get anywhere at all. The exception to this is if you are able to refuel your rocket while in orbit already.

This is the plan for Starship: in-orbit refueling. It’s a step so critical to leaving our planet behind that NASA has announced that they will work with SpaceX to tackle the problem. The SpaceX plan is to send up a single Starship into orbit first. Then additional tanker Starships will be sent up in sequence afterward. These tankers will rendezvous with the first Starship and transfer their excess fuel into it. In this way, Starship will double its capacity to visit other destinations in the solar system.

In-orbit refueling will not be easy. The task of automatic docking has been demonstrated to be within SpaceX’s capability with the Dragon demo missions to the International Space Station, but transferring large amounts of propellant between two spacecraft of this size has never been done before. In space, liquids tend to spread out within their containers. It will take a great deal of coordination between the two Starships to pull the maneuver off.

Article source: avaruus.fi and thomasnet.com

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