This article explains in a nutshell why the ONESTAGETOSPACE MARVEL rocket launcher reaches a much higher performance in a vehicle the size of a Falcon 9.
The secret? An overlooked take on rocket staging that helps our ONESTAGETOSPACE rocket concept beat the competition on cost, reuse and performance using a simpler design.
Rocket staging improves the amount of payload a rocket can bring to orbit. This is because every kg of mass brought to orbit requires up to about 20 kg of propellant (very rough indicative numbers, abstraction of staging, propellant types, thrust levels, altitude compensation or not, and ISP)
But why reinvent the wheel? This is how wikipedia explains the main advantage and disadvantage of staging:
Advantage of staging
“The main reason for multi-stage rockets and boosters is that once the fuel is exhausted, the space and structure which contained it and the motors themselves are useless and only add weight to the vehicle which slows down its future acceleration. By dropping the stages which are no longer useful to the mission, the rocket lightens itself. The thrust of subsequent stages is able to provide more acceleration than if the earlier stage were still attached, or a single, large rocket would be capable of. When a stage drops off, the rest of the rocket is still traveling near the speed that the whole assembly reached at burn-out time. This means that it needs less total fuel to reach a given velocity and/or altitude.”
Disadvantage of staging
“On the downside, staging requires the vehicle to lift motors which are not yet being used, as well as making the entire rocket more complex and harder to build. In addition, each staging event is a significant point of failure during a launch, with the possibility of separation failure, ignition failure, and stage collision. Nevertheless, the savings are so great that every rocket ever used to deliver a payload into orbit has had staging of some sort.”
It is with regards to preventing the downside that ONESTAGETOSPACE’s MARVEL offers a breakthrough:
Since we put the altitude adaptive engines at the top, and thus only have a single engined stage, we can use drop tanks instead of engined stages. This conceptual change leads in a windfall of downstream advantages:
- We can drop the drop tanks on the go, lightening the entire vehicle;
- We can use multiple very simple drop tanks, each structurally weighing about a metric ton;
- Drop tanks do not need expensive avionics, control surfaces, nor expensive engines and their complicated plumbing;
- They are low-cost mass producible items;
- If we use a gaseous propellant or fuel in the lower drop tanks, which uses pressure to evacuate the propellant, then the plumbing becomes almost as simple as linking and jettisoning inline camping gaz pressurized fillings;
- The drop tanks can be parachuted from very low altitude;
- Especially drop tanks dropped from lower altitude will not see important stresses, which will enhance their chances of being refurbishable or 100% reusable after simple inspections.
- The fact that the upper stage, the single engined stage, now requires more engines and thus is heavier, is offset by the fact that the vehicle requires less engines overall. Equally less structural weight, overall, needs to be accelerated to orbital speeds of a given fraction thereof, resulting in reduced propellant requirements.
- The design as a whole uses structural mass more efficiently
These combinations of approaches synergistically lead to a much improved performance. Dropping one ton of structural mass early in flight, can lead to up to 1 metric ton of payload increase in orbit for the same overall vehicle weight. Subsequent drop tank staging, at a later stage in the ascent, leads to a degressive increase of payload to orbit (the incremental advantage becomes smaller), but, when repeated enough, it still leads to a massive overall payload increase that is very advantageous to the profitability of the launcher.
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