The first thing to consider when planning a space trip is why we want to undertake it and what we expect to gain from the findings.
The following issues concern the enterprise's viability, as indicated by the following questions:
- How much does it set you back?
- Is it reasonably priced?
- Can it be done technically (and politically)?
- How safe is it, and what are the chances of it failing?
- Can we launch (and potentially build) the necessary vehicles in space?
Without putting in a lot of time and effort into early research and modeling, even rough solutions to these issues are difficult to come by.
Additionally, there are a variety of architectural variants in space ships, their sequencing, phasing, and destinations that may be used to carry out such a space mission.
“Mission architectures” or simply “architectures” are the terms used to describe these different variants. Conducting thorough studies of each possible architectural alternative would require substantial financial resources as well as a significant amount of time and work.
- Furthermore, while planning a human trip to Mars, it is virtually difficult to predict what the status of marginal technologies like nuclear propulsion and large-scale aero entry will be many decades from now.
- As a result, the most common method includes a rudimentary first study to evaluate architectural alternatives, from which a small selection of preferred designs may be determined that should be investigated further.
The initial mass in low Earth orbit (IMLEO) is often used as an approximate gauge of mission cost in early planning, and since IMLEO can generally be predicted to some degree, it is frequently used as a proxy for mission cost.
- This is predicated on the idea that when comparing a set of possible missions to accomplish a given objective, the quantity of "stuff" that has to be transported to LEO is a significant driver of the cost.
- IMLEO is the overall mass in LEO at the start, but it doesn't say how that total mass is divided up into individual vehicles.
- Unless on-orbit assembly is used, the mass of the biggest spacecraft in LEO determines the requirements for launch vehicle capacity (how much mass a launch vehicle must lift in “one fell swoop”).
As a result, the early planning of space missions, as well as the preliminary selection of mission designs, is based on two linked parameters:
(1) IMLEO, and
(2) the necessary launch vehicle and number of launches.
It's critical to realize that the requirements for space missions are driven by the need for vehicles to accelerate to great speeds.
- Unlike a car, which has a big crew compartment and a tiny petrol tank, most spacecraft have huge propellant tanks and a small crew cabin.
- A space mission is made up of many propulsion stages, each of which contains more propellants than cargo.
Each propulsion step necessitates the acceleration of both the cargo and the propellants set aside for subsequent acceleration steps.
- As a consequence, the majority of IMLEO is spent on propellants rather than payload.
- The quantity of propellants transported to LEO to go from here to there (and back) becomes (at least in part) the decisive element in evaluating whether a space mission is possible and economical.
- As we previously said, this is reflected in the value of IMLEO, which is mostly comprised of propellants rather than payload.
- This image may alter in the future if we can effectively deliver propellants to LEO.
~ Jai Krishna Ponnappan
You may also want to read more about Space Missions and Systems here.
