Universal Craft vs. Mission-Designed Craft

[Valley]

In playing KSP I have slowly discovered that making rockets or craft designed to do everything, like my Trucker models, seems to be a real problem when compared to making different crafts or rockets for different goals. In other words, trying to make a craft that can delivery a payload, act as a tug, go to the Mun, or help refuel as station is ten times harder than making a different space-craft for each mission.

In the real world, that is what NASA tried to do with the Shuttle program - make a workhorse, a mule, that could do everything. It failed.

But is there a way it could be done? For example, putting a payload into orbit has to be done again and again, cheaply, for a space program to get 'off the ground'. A universal rocket is something NASA and other agencies around the world are always working on (SLS for example). But is it a pipe dream to think about making a rocket that could take people to the Moon, Mars, Jupiter?

[Dkmdlb]

Universal lifters are the easiest thing to do in terms of universalizing space fligth. That's the idea behind the ULA's Common Booster Core and common upper stage. Design a modular solid booster, a modular core stage, and a modular upper stage, and you can lift anything from small payloads to big 'o interplanetary transfer stages.

A SLS block 2 sized rocket could be the common rocket for going to all those places. A moon trip would require one launch, a Mars trip might require 2, let's say (transfer stage + hab), and a Jupiter mission might require 3 (transfer stage, auxiliary tank, and hab).

You could use a common transfer stage to get to the various destinations in the solar system, and add additional fuel tanks as necessary.

[Mitchz95]

Depends on what you want to do there. If the purpose of visiting all three destinations is to conduct long-term research, you could probably get away with just adding/removing fuel and life support. Making the payloads modular would also be useful.

[shynung]

Rockets used for launch vehicles are generally heavily standardized, while spacecrafts are usually specialized for the mission they are planned to conduct. This is because for a launch vehicle, the mission is almost always the same: put payload X to LEO/GTO/TLI/whatever trajectory the client asked, and the performance margins are pretty small. Most of their development consists of trying to squeeze as much delta-V as possible while keeping costs down, all while keeping the rocket itself from exploding before the mission is done.

Spacecrafts, on the other hand, have a far wider variety of missions, from a simple communications satellite all the way to rovers, space probes, and manned landers. Compared to a launch vehicle, the dV requirements are lower, and the spacecrafts themselves must be able to do more than simply flying there, like transmitting signals or obtaining data from sensors. For this reason, the spacecraft's equipment are much more complicated than that of a launch vehicle, and generally different from other spacecrafts, custom fitted for the mission conducted in order to lower total mass as much as possible, conserving propellant needs for the same dV.

[xenomorph555]

Firstly are we talking rockets, probe/sats or manned spacecraft.

If we are talking rockets, then the term universal rocket basically revolves around a rocket having a number of common components that can be stacked together in different ways to suit different missions, not a large single rocket design to do everything. Examples are LM-5 series, Angara series and to a lesser extent Falcon 9.

Probes/sats wise most designs are universal and can do most tasks. Chang'e 1, 2, 5-T1 and Chandryaan, Manglyaan are modified designs of heavily used communication sats that just happen to be good enough to go to deep space.

Manned craft wise Apollo and Soyuz are very universal, both are capable of doing a LEO mission, visit a station or go to the moon.

[Bill Phil]

The Shuttle only failed because it was the only thing funded. If the space station planned in 1969 was done the shuttle would have been necessary. It also failed because the USAF got involved...

Besides that, a generalized spacecraft is just that, generalized. Excels at nothing. So a mission built craft will always be better, but it might not be a good interplanetary tug.

[rhoark]

I like to think that the space shuttle succeeded less thoroughly than it could have.

[Newt]

Well, the shuttle was plagued by a number of problems, funding being one of them. If you want to talk about that, start a different thread, or find an older one.

Cars are mass produced vehicles, used by many people in a diverse number of situations. The same car can be designed to operate in snow, or in swamps, at high altitudes or in the Dead Sea, as a personal transport, a cargo vehicle, a police car et cetera, with very little modification. This is possible, largely because we have the leisure of adding features and capabilities that most people do not use. This is the case for, among other things, the reason that cars are both in demand. People in many places do well to have cars for all sorts of purposes, and, when mass produced, cars are viable to sell to many people the world over.

Spacecraft are not like this. Spacecraft are expensive, and far from in demand. As a consequence, those who use them often make them themselves, and make them for a very particular purpose; flying to the Moon, to Mars, to visit a comet et cetera, and those spacecraft are designed, out of necessity to do only that which is required of them; every gram should be used, and no weight is spent on useless features. This means that they are usually extremely specialized, not that a Mars orbiter could not be useful at Jupiter, but that people want the instruments and abilities to do just what they want, and so when going to Mars it is prudent to design a vehicle just to ask the Mars questions

The main place where this is changing perhaps is the region of LEO, where spacecraft buses can be used as a standard framework to build a satellite with. I imagine, in the future it will further change, as it is more practical to frequently visit more distant places, and more people will have the ability to send more distant probes.

[EzinX]

One of the reasons what you have tried to do has failed is because KSP does not have a good way to "package up" a payload into a real fairing that structural supports all the parts inside correctly. If you could package a wide variety of mission payloads into a universal payload fairing, where KSP would model the forces on the outside of the payload fairing only, and assume that all payload inside was "strapped down" and unable to move at all in any dimension (realistic), it would be much easier. With these "universal" payload fairings, all launches of a rocket would be consistent every time. In fact, you could even make the fairings automatically have ballast added to them so that they always weigh the same even if the payload is lighter than the max capacity of the fairing.

Has any mod already done this?

[King Arthur]

There's an old saying: Jack of all trades, master of none.

It's certainly possible to design a single craft that can be versatile in the things it can do, but inevitably the design process will be harder (the F-35 Lightning II is a particularly bad example of this) and its performance in any given thing will almost always be inferior if compared to a craft that was specifically designed for a specific purpose.

[shynung]

There are places where a jack-of-all-trades craft would be useful. In the wars currently waged on the Middle East, F-16 fighter jets have been used for anything from air defense missions to ground attack missions, i.e. 'bomb trucks'. The advantage is that the same asset can be used for a variety of purposes, often at the expense of the craft's mission-related performance (number of bombs/missiles carried compared to a specialized air defense/ground attack jets). In cases where the all-purpose craft has been mass-produced anyway, a common tactic of reducing the lowered performance is to deploy multiple crafts for the same mission. This is less efficient than sending in a single special-purpose craft that have better performance, but simpler from a logistics standpoint, to further reap the benefits of economies of scale.

[Nuke]

i like to draw a line between launch vehicles and space craft. the former are rather interchangeable, so long as the launch vehicle can deliver your required tonnage you are fine. things like ssto, space planes, and rockets all belong to that category. their job is simply to get things on the ground and haul them to orbit. space craft currently have to be very mission specific, designed with specific tasks, delivering rovers to mars or landing things on comets.

eventually we will get to the point where we have a standard probe that has the best technology you can get all crammed into a tiny package, just attach whatever size fuel tank you need and you got a ship. problem with that is that technology is always moving forward, so a probe you launch last year is obsolete the next (and add 10 years of obsolescence on top of that for making the technology rad hard). when the required technologies reach their optimal point, then doing a standard probe becomes possible.

id love to see reusable transfer vehicles but that would likely require better power systems, so you can drive power hungry electric propulsion (on the order of megawatts to gigawatts) with really high isp engines. but that kind of thing is decades away (probibly requiring breakthroughs in fusion, or offworld nuclear fuel production for fission reactors).

for the time being its better to just do a custom build, then strap on as many off the shelf components that your mission calls for.

[kahlzun]

I managed to build a series of omnicraft that could travel anywhere. Regarded that as my best achievements at the time, which was around 0.18

[Nibb31]

I'm afraid another poor example of a "multipurpose exploration vehicle" is Orion.

Orion was designed originally with the mission of travelling to the Moon and back. "Apollo on steroids" was the mantra at the time. It is scaled for 21-day missions, supporting 4 crew members, high-speed reentry, contingency EVA, and radiation shielding. And that's it.

Other than going to the moon, it isn't really multipurpose, because you can't use it for much else. It's too expensive and over-engineered for LEO sorties. It can't be used for servicing or repair missions because it can't carry cargo or a manipulator arm. For interplanetary missions, it is either too small as a standalone craft or over-engineered as tender for a larger MTV.

[rhoark]

NASA has been blowing a lot of PR smoke about how Orion is going to Mars, but the fact is that it's a single component with a very specific purpose: re-entering Earth's atmosphere from a circumlunar or interplanetary trajectory. Everything else about a mission to Mars would have to be provided by other hardware.