[X] My Assistant

[karolp]

So, in the 1960s we did it like that:

1. sending single, big spacecraft of very limited, one purpose capability and limited lifespan
2. not being able to re-use the spacecraft for other targets
3. no means of controlling the situation when something goes wrong at landing etc.
4. not being able to see the spacecraft from orbit
5. designing each spacecraft from scratch instead of reusing and further developing existing designs

All in all, this resulted in:

A. a lot of failed missions and wasted money and effort
B. only limited scientific results which usually required follow-up missions which still were inconclusive
C. very expensive missions that took years to develop and perished in seconds if something went wrong

We may have made some progress in some points with missions like MRO which can see ground spacecraft from orbit or even take snapshots of spacecraft landing in progress (Phoenix). However, this is still occasional "byproduct" and not a change in philosophy. Therefore, I'd like to suggest creating a more general thread about the specific issues listed in the first paragraph.

Let's face it, we still do relatively expensive planetary probes which still provide us only with limited "beachhead" kind of scientific results and do not have a lot of maneuvering capability nor planning flexibility.

Here are a few suggestions which I would love to see discussed by people who know more than me about space exploration technology:

1. first and foremost: no more single, big and expensive, heavy spacecraft

Instead of taking one big rover on board, we could take one small rover, one small airplane and a cluster of microbots designed for specific purposes - each providing valuable data in many areas simultanously and if one is dead, there are still plenty of others to continue the mission.

2. a spececraft already there is better than one on the drawing board

No more short lifespans. Each mission should be designed while keeping in mind that money for future missions and follow-ups may not be available. Accumulating a lot of data over a lot of time gives us insight into how things CHANGE over time on a given target.

3. no more fly-by expendable spacecraft

Flying by a planet to see what it looks like and letting the spacecraft then fly into oblivion may have been a good idea back in the early days but not any more. I tend to regard this kind of approach as extremely short-sighted, providing only short-term gains which do not balance the cost and effort involved. I think we need spacecraft that is finally able to MANEUVER itself, meaning it has its own propulsion of some kind, be it only a weak ion thruster.

This way we could actually GO PLACES rather than select one target and writing off an entire spacecraft after this target is examined. Reusing Stardust and Deep Impact were good examples of this approach. However, I think this should be a default capability of every spacecraft rather than counting on pure luck and coincidence in selecting additional targets.

Imagine the Voyagers being able to come back to their previous targets or Galileo setting itself free of Jupiter's gravity and going out to explore asteroids instead of plunging into its fiery demise.

4. no more single-spacecraft "hope it works" approach

Instead of sending just one orbiter or one lander, we should send a lander and an orbiter simultanously so that we have the possibility of tracking spacecraft as it lands and inspecting it afterwards. No more "lost spacecraft stuck somewhere". We could aim at making spaceraft COOPERATE not by coincidence but from the start.

Let me give you a nice example: imagine we might send a new orbiter and a new lander to Titan. Obviously the orbiter will provide data link capability and some basic radio tracking. But would it not be wiser to actually fit it with a decent camera that allows it to actually SEE the spaceraft if something goes wrong?

I shall go into more detail on that in another thread:

http://www.unmannedspaceflight.com/index.php?showtopic=5820

Do not worry, I won't fill the forums with lots of my threads of this kind, just this one and another one for some of the things that had been on my mind for some time now.

And finally:

5. no more reinventing the wheel each time we go somewhere

Of course each mission has its specific goals, but modifying an existing design might actually be cheaper in a lot of cases. And most of all: there is nothing wrong in sending identical spacecraft to two different asteroids

[dvandorn]

This has been discussed a number of times here, and most all of your points have been addressed. And, I must say, there are several areas in which you are not correct in your assumptions.

First, you're generally incorrect about "how we did it in the 1960s." The first successful American planetary probe, Mariner 2, was a Ranger Block II spacecraft fitted with a large parabolic antenna and some alternative sensors to those generally carried by the early Rangers. It was not custom-designed for a mission to Venus, and nearly succumbed to the increasing solar constant as it approached our nearest planetary neighbor.

We planned entire series of spacecraft for given missions back in the 60s. Each of the first three American attempts to reach Mars were designed as dual-spacecraft missions. Mariners 3 and 8 never even got into Earth orbit, but there were originally to be flotillas of Mariners 3 and 4, 6 and 7, and finally 8 and 9.

Ranger, Lunar Orbiter and Surveyor lunar probes were designed as a series of missions to be flown by the same base spacecraft, with minor changes to the sensor packages between flights. And this was even rather program-specific; all five Lunar Orbiters were nearly identical, the Surveyors only differed in the various experiments attached, and Ranger went through five spacecraft iterations, only one of which (the Block V) actually succeeded.

Even into the 70s, we sent pairs of spacecraft on every mission. Vikings 1 and 2, Pioneers 10 and 11, Voyagers 1 and 2. And as for not knowing what's happening during critical events such as landings, our ability to monitor such things back in the 60s had a lot more to do with limitations of communications and data processing techniques. Once we developed ways of monitoring these mission segments, we started doing it.

It wasn't just the pairs of spacecraft on a given mission that shared design elements -- Mariners used the same octagonal spacecraft bus starting with Mariner 3 and ending with Mariner 9, and even the Voyagers house their "guts" in octagonal buses that are similar in size to the first Mariner ever designed.

By saying "never re-invent the wheel again," you put on blinders that don't let you take advantage of new developments in a variety of engineering and scientific fields. It makes absolutely no sense to be forced to carry forward antiquated power, imaging, data processing or propulsion technologies. And trust me, it's not just a matter of "Hey, just fly Cassini or MER or Galileo again and just update whatever has been improved in the meantime." Once you factor in such technology advances, you end up re-engineering a "carry-forward" design so much that you're essentially designing a new vehicle every time.

Now, I'm speaking primarily of the American program. If you want to argue any illogic to the progression of the Soviet planetary exploration program, you need to read up on how the Soviet system worked -- there was little to no actual planning in terms of progressions of missions, each building upon the last. Each Soviet probe was an engineering demonstration championed by a specific design bureau, or most often by the little kingdom-holder of a given design bureau. As with many things, the Soviet space program reflected a nearly Byzantine maze of personal relationships and antagonisms more than it did a well-thought-out plan for planetary exploration.

So, I would agree that we ought not do many of the things you say we ought not do, Karol. The problem is, we didn't do those things back in the '60s. Please read your histories a little more thoroughly...

Why don't we send things in twos any more? Without exception, it's because of cost. When your launch vehicle accounts for a good 40% to 60% of your total mission cost, you just often can't afford to use two of them. And the MER experience tells you pretty solidly that it *does* take nearly twice as much money to make two of something as it does to make just one.

As for your insistence that we only send little tiny probes, micro-robots, things with limited resources, but with robust designs, well, that really limits what you can get out of a mission. If you're going to spend $100 million for a booster, you need to get as much as you can out of the spacecraft you're delivering. And the best example of a "small" rover vs. a "big" rover would be Sojourner vs. MER. I don't care if you landed three Sojourners at each of the MER landing sites, you would *never* have gotten the amount of science out of them that you've gotten out of the MERs. (In general, "small" means more limited, less able to handle adverse or unforeseen conditions, less capable -- be wary when recommending such approaches, as far too many *failed* missions have ascribed to that philosophy.)

-the other Doug