Parasite Spacecraft....Virtually Essential For Manned Spaceships

[Spacescifi]

 

How many times in scifi shows do you see a scifi spaceship fly up close to a derelict spacecraft and engage a tractor beam to pull in something it wants? 

Even if such were possible neither may be optimal if real physics are in play because:

1. A big spaceship's main drive may be radioactive and blow very hot exhaust. You do not want that anywhere near floating astronauts in space you are trying to rescue. Even using auxillary rocket exaust from a big vessel near floating astronauts can be problematic as it may blow them farther away. Retroburning to slow down is very much a thing in space travel.

2. Small shuttlecraft are quicker about speed changes at short distances because they have lower inertia, as less mass equals less inertia a propulsion system has to push against. Same reason why surface to air missiles have less thrust overall compared to Spacex' Starship but have much higher acceleration.

3. Even if you have a drive so scifi that it does not generate harmful exhaust nor will it blow around astronauts or debris you want to pick up....a shuttlecraft is arguably still an easier low tech solution. Simple and rugged seems to always win out over overengineered complexity when a solution is fairly straightforward.

Conclusion: No matter how fictional or realistic a scifi spaceship is, parasite craft are a force multiplier for bringing stuff inside your vessel. Arguably better than using grapoeling arms or even tractor beams. I think those are best used for hauling or pushing objects too big to put inside..

 

Edited June 3, 2021 by Spacescifi

[magnemoe]

Agree with parasite crafts if your ship is large, thing the cycler in the Martian or larger.  They are even more useful on an space station there I could see something more like tugs used. Think the orion pulse nuclear had them too who makes plenty of sense. 
So my larger space stations and orions in KSP tend to have an rcs tug. 

[KSK]

7 hours ago, Spacescifi said:

How many times in scifi shows do you see a scifi spaceship fly up close to a derelict spacecraft and engage a tractor beam to pull in something it wants? 

Even if such were possible neither may be optimal if real physics are in play because:

1. A big spaceship's main drive may be radioactive and blow very hot exhaust. You do not want that anywhere near floating astronauts in space you are trying to rescue. Even using auxillary rocket exaust from a big vessel near floating astronauts can be problematic as it may blow them farther away. Retroburning to slow down is very much a thing in space travel.

2. Small shuttlecraft are quicker about speed changes at short distances because they have lower inertia, as less mass equals less inertia a propulsion system has to push against. Same reason why surface to air missiles have less thrust overall compared to Spacex' Starship but have much higher acceleration.

3. Even if you have a drive so scifi that it does not generate harmful exhaust nor will it blow around astronauts or debris you want to pick up....a shuttlecraft is arguably still an easier low tech solution. Simple and rugged seems to always win out over overengineered complexity when a solution is fairly straightforward.

Conclusion: No matter how fictional or realistic a scifi spaceship is, parasite craft are a force multiplier for bringing stuff inside your vessel. Arguably better than using grapoeling arms or even tractor beams. I think those are best used for hauling or pushing objects too big to put inside..

 

Nothing wrong with shuttlecraft or other auxiliary vessels. However your conclusion is an over-generalization that does not follow on from your reasoning.  Apart from anything else, you make an entirely arbitrary choice about the way you want tractor beams to work and use that as a justification for your statement that parasite craft(?) are a force multiplier for bringing stuff inside a vessel, no matter how fictional or realistic it is. 

Also, if real physics are in play, then an auxiliary vessel adds mass and complexity to the vessel it's auxiliary too. Is that an acceptable tradeoff for the extra utility it provides?  Impossible to tell without knowing a lot more detail, in which case the answer becomes 'yes it's acceptable under these circumstances' which defeats your conclusion that the auxiliary vessel is always a force multiplier.

Taking the rest of your points in turn.

1.  Yes,  a significant exhaust plume would be a disadvantage here. The obvious way around that is to use the main drive to match trajectories with whatever one is picking up but to come to rest (relative to that thing) at a safe distance. Then use maneuvering thrusters to close the gap.  Locating or angling those thrusters so that they don't impinge on the item to be collected is reasonably straightforward.  Besides, unless the auxiliary vessel is limited to using maneuvering thrusters only, then it will likely have a main drive of its own which again will need to be taken into account.  

2.  Possibly, maybe even probably, but not necessarily. If one ship has half the mass of another but its engines also generate half as much force, then it will accelerate at the same rate.

3.  Unless that sci-fi drive has other unspecified limitations that make it unsafe to use in this context, then using a separate vessel could easily be adding complexity here. Simple and rugged is great if you can use it as an alternative to a complex over-engineered solution, but here you need to use both.

[Nuke]

landing large space craft really doesn't make a lot of sense. 

[Spacescifi]

3 hours ago, KSK said:

Nothing wrong with shuttlecraft or other auxiliary vessels. However your conclusion is an over-generalization that does not follow on from your reasoning.  Apart from anything else, you make an entirely arbitrary choice about the way you want tractor beams to work and use that as a justification for your statement that parasite craft(?) are a force multiplier for bringing stuff inside a vessel, no matter how fictional or realistic it is. 

Also, if real physics are in play, then an auxiliary vessel adds mass and complexity to the vessel it's auxiliary too. Is that an acceptable tradeoff for the extra utility it provides?  Impossible to tell without knowing a lot more detail, in which case the answer becomes 'yes it's acceptable under these circumstances' which defeats your conclusion that the auxiliary vessel is always a force multiplier.

Taking the rest of your points in turn.

1.  Yes,  a significant exhaust plume would be a disadvantage here. The obvious way around that is to use the main drive to match trajectories with whatever one is picking up but to come to rest (relative to that thing) at a safe distance. Then use maneuvering thrusters to close the gap.  Locating or angling those thrusters so that they don't impinge on the item to be collected is reasonably straightforward.  Besides, unless the auxiliary vessel is limited to using maneuvering thrusters only, then it will likely have a main drive of its own which again will need to be taken into account.  

2.  Possibly, maybe even probably, but not necessarily. If one ship has half the mass of another but its engines also generate half as much force, then it will accelerate at the same rate.

3.  Unless that sci-fi drive has other unspecified limitations that make it unsafe to use in this context, then using a separate vessel could easily be adding complexity here. Simple and rugged is great if you can use it as an alternative to a complex over-engineered solution, but here you need to use both.

 

Stuff like the following is what I am talking about. Problem could have been solved easily if they had even NASA craft lodged in the ship...which is far below the scifi stuff they use:

Could not find a video, but in Stargate SG1 on a late season episode Carter was floating in space and the main vessel's teleporter was fried in battle.

Since they never bothered to put even rudimentary NASA type parasite craft aboard, they had to literally fly the big ship so it's cargo bay swallowed her.

 

Problem was that it's lowest thrust setting was still kind of high,   so they had to burn for about a sec and coast the rest of the way .

2 hours ago, Nuke said:

landing large space craft really doesn't make a lot of sense. 

 

Generally unless you plan to stay or your delta va and thrust are just that good.....bettee to land on ocean then since high thrust/high delta v equals landing in lava.

[KSK]

But the problem was still solved right? It could have been made easier but a parasite craft (bizarre wording by the way) wasn't actually required? 

Anyway, it sounds like you have some specific scenarios in mind where having a shuttlecraft along would be useful or even essential. That's great - as I said right at the start of my post, there's nothing wrong with shuttlecraft. But there's a long way from there to a general assertion that "No matter how fictional or realistic a scifi spaceship is, parasite craft are a force multiplier for bringing stuff inside your vessel. "

[Spacescifi]

23 minutes ago, KSK said:

But the problem was still solved right? It could have been made easier but a parasite craft (bizarre wording by the way) wasn't actually required? 

Anyway, it sounds like you have some specific scenarios in mind where having a shuttlecraft along would be useful or even essential. That's great - as I said right at the start of my post, there's nothing wrong with shuttlecraft. But there's a long way from there to a general assertion that "No matter how fictional or realistic a scifi spaceship is, parasite craft are a force multiplier for bringing stuff inside your vessel. "

 

I grant you that....I just think many a plot could be solved easier if parasite craft were available.

 

Examples:

Stowaway: Scott Manley's recent contributed help movie. Really they needed a a robot with manipulators and RCS, then Anna Kendrick would not have died.

The Martian: If the crew had parasite craft Matt Damon would not have needed to play Ironman in space with his hand gloves.

 

I am sure there are mode examples. Overall I think if you cannot manage to have the extra mass of parasite craft onboard, then any disaster you find yourself in later will be all that much more critical.

 

 

 

 

 

 

 

[jimmymcgoochie]

S1 Ep1 The Expanse: Canterbury is parked, grabbing ice from Saturn’s rings with big robot arms and storing it inside its hold. Not a tractor beam or auxiliary craft in sight, just oversized litter-pickers. The Expanse also covers a lot of the rendezvous stuff too- torch drives burning to within close range and matching most of the speed then complete the velocity matching and docking with RCS, not unlike your typical KSP docking.

Re. The Martian, what is that EVA jetpack chair if not an auxiliary craft? Yes it’s tethered to the Hermes, but only for safety- it would have been possible to fly that over to the MAV, grab Witney and fly back.

Stowaway is a bad example- why would they add a robot with RCS and a set of arms sophisticated enough to gain access to the booster’s lox tank and siphon it off, just on a random hunch that it might at some point be a useful thing to have on board? A simpler solution- a winch and cable running down one of the tethers- would allow access to both the core and the booster when it was spinning without the risk of sliding down and crashing to the bottom potentially damaging you and/or the spacecraft, but why would they ever need to go to the hub or the booster when it was spinning?

If you have a magic warp drive, you can afford to carry around the excess weight of every “just in case” gizmo you like, but if not it’s just dead weight that’ll slow you down and potentially mean you don’t get where you’re going; see Stowaway, where the excess weight nearly caused them to abort the mission.

[Spacescifi]

33 minutes ago, jimmymcgoochie said:

S1 Ep1 The Expanse: Canterbury is parked, grabbing ice from Saturn’s rings with big robot arms and storing it inside its hold. Not a tractor beam or auxiliary craft in sight, just oversized litter-pickers. The Expanse also covers a lot of the rendezvous stuff too- torch drives burning to within close range and matching most of the speed then complete the velocity matching and docking with RCS, not unlike your typical KSP docking.

Re. The Martian, what is that EVA jetpack chair if not an auxiliary craft? Yes it’s tethered to the Hermes, but only for safety- it would have been possible to fly that over to the MAV, grab Witney and fly back.

Stowaway is a bad example- why would they add a robot with RCS and a set of arms sophisticated enough to gain access to the booster’s lox tank and siphon it off, just on a random hunch that it might at some point be a useful thing to have on board? A simpler solution- a winch and cable running down one of the tethers- would allow access to both the core and the booster when it was spinning without the risk of sliding down and crashing to the bottom potentially damaging you and/or the spacecraft, but why would they ever need to go to the hub or the booster when it was spinning?

If you have a magic warp drive, you can afford to carry around the excess weight of every “just in case” gizmo you like, but if not it’s just dead weight that’ll slow you down and potentially mean you don’t get where you’re going; see Stowaway, where the excess weight nearly caused them to abort the mission.

 

True....Stowaway is bad design all the way around.

 

Like that is not something a government agency would mess up to that degree I do not think. A corporate entity? Sure...and that is essentially who the foolish people at he top were in the movie. Probably trying to cut costs, certainly looks that way.

I am certain that were it to happen IRL Anna Kendrick's character's family would sue that company and ruin their reputation assuming they did not pay them enough to stay quiet.

[KSK]

7 hours ago, jimmymcgoochie said:

Re. The Martian, what is that EVA jetpack chair if not an auxiliary craft? Yes it’s tethered to the Hermes, but only for safety- it would have been possible to fly that over to the MAV, grab Watney and fly back.

If you have a magic warp drive, you can afford to carry around the excess weight of every “just in case” gizmo you like, but if not it’s just dead weight that’ll slow you down and potentially mean you don’t get where you’re going; see Stowaway, where the excess weight nearly caused them to abort the mission.

Which is exactly what they did in the book. They used the maneuvering thrusters to get Hermes as close as they could to Watney whilst still leaving a (just) acceptable reserve,  breached the hull as an emergency effort (escaping air created thrust) to slow down to a viable intercept velocity, then sent a crewmember over on a tethered MMU to collect Watney.

You could have a reasonable debate about where to draw the line but to be called an auxiliary craft, I'd say that any crew need to be able to work in a shirtsleeves environment inside. Whether that's necessarily wise or not is another matter. EVA suits, Manned Maneuvering Units and the like don't quite count for me but maybe that's just me.

But your last point hits the nail on the head in my opinion. If your spacecraft is large enough or capable enough that the mass of a 'just-in-case' auxiliary craft can be accommodated, then sure - why not take one. Otherwise it becomes a matter of tradeoffs. In The Martian for example, I would argue that even if Hermes had had the capacity to take an emergency shuttlecraft along just in case they needed to rescue a crew member under highly unforeseen circumstances, it would have been better to use that excess capacity to take along more life-support supplies or thruster fuel, as both are more generally useful for covering a range of emergency situations rather than one specific situation.

Oh - and on the topic of big bad cost-cutting corporations vs government agencies. Apart from being the biggest, laziest cliche in the book, I would point out that, thus far in history, the majority of spaceflight fatalities have been caused by poor and, in some cases entirely unforced, government agency decisions. 

Edited June 4, 2021 by KSK

[Nuke]

21 hours ago, Spacescifi said:

Generally unless you plan to stay or your delta va and thrust are just that good.....bettee to land on ocean then since high thrust/high delta v equals landing in lava.

theres that. though there is the possibility of actively cooled landing pads which can handle some pretty nasty thrust. 

there are a few situations that might warrant landing even with large ships. maintenance and scrapping for example or disgorging large amounts of cargo from a large freighter. i imagine all these would be done at low gravity depots (say the moon for example). delivery to a ring station or even to a freight yard orbit might also be options. would be very situational. say you are delivering freight to an outpost without a lot of infrastructure. say they dont have any orbital infrastructure at all. if you are just dropping off, orbital drop pods would probibly be adequate. but if you also had to bring freight up the well, then a lot of back and fourth flights with a few onboard shuttles would take an eternity and would end up using almost as much fuel if not more (you need to get your shuttles back up for the next load with exports in tow, multiple times). a destination with more infrastructure might just have a terminal in orbit for that kind of thing. 

[Vanamonde]

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