Mini-Missiles and Fast Characters

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CoalPoweredPuppet CoalPoweredPuppet's picture
Mini-Missiles and Fast Characters

I have a player who has fallen in love with mini-missiles, and one possible bad he might run into is in a Fury Morph. If, given the Fury is aware of the threat and "readies" her action, could she catch the missile before it hits her? What would be the roll to do so? Would it require specialized augmentations or programs?

A few things I know would factor in:

  • most missiles of this kind would be contact triggers for the explosives, though proximity triggers would be possible.

  • Proximity and laser/energy guided systems would imply a certain bonus to hit, which could be factored into the smart link. Not sure if this would render the catch pointless.

  • The game doesn't list a meters per second for the missiles because its usually pointless. This seems to imply the missiles travels at the speed comparable to a bullet, or at least fast enough it shouldn't matter.

  • And since the target would be visible on the hero's TACNET- which could be linked to the missile- that could also set the missile off in the Fury's grip.

Lazarus Lazarus's picture
I am really tempted to post

I am really tempted to post hysterical laughter as a response to this but that is pretty unfair. Many of us have grown up conditioned by years of watching television where we watch someone look out a window, spot someone on the rooftop across the street firing an RPG-7, then as we watch the grenade (which is basically a small missile) streak across the street the hero dives out of the room moments before the room is engulfed in fire.

An RPG-7 has a flight velocity of about 300 m/s, which equates to about 675 miles per hour for people stuck in the Imperial system. I guess you could say it is comparable to a bullet, but you are definitely on the low end of things (I mean, I suppose an arrow is comparable to a bullet, it's just that the comparison is a fraction). It is, however, clearly too fast for anyone to catch, at least under normal combat conditions. The whole idea of people being able to dive out of the room (or pretty much have almost any sort of meaningful reaction to a fired RPG before it can reach them) is just Hollywood BS (a quick glance at what I consider a typical Downtown street on Google Maps shows it to be 20 meters wide, so it would take about 1/15th of a second for the RPG to cross the street).

I should note that I'm assuming an RPG-7 has roughly ithe same performance as a 'mini-missile' because the ranges roughly line up with what an RPG-7 could probably perform if it had a guidance function. I feel that they are at least close enough that the numbers have some validity. Maybe a mini-missile tops out at only around 200 m/s, but that is still way too fast for someone to catch.

Sizewise the round of an RPG-7 is probably closer to a standard missile (usable from a disposable launcher) though its antiquated technology severely impacts its range (since it can't course correct) and likely its damage and armor piercing capabilities.

My artificially intelligent spaceship is psychic. Your argument it invalid.

CoalPoweredPuppet CoalPoweredPuppet's picture
True...but...

I agree with you, especially when talking about how very, very fast RPG/mini-missiles are. But I'm not talking about a normal, or even exception bad guy. The Fury Morph has amp'ed up reflexes and the body is designed for combat. Add in some wicked tailored drugs (to bypass the toxin filters) and she is very, very fast. Hence, my question.

However, it does seem like you would put this idea solidly in the "no" category. Its a hard argument to counter.

Lazarus Lazarus's picture
Even if you were to divide

Even if you were to divide the velocity by 4 (to account for their Speed of 4) you are looking at over 165 miles per hour, which is a bit faster than an arrow fired from a recurved bow. Mythbusters did something a while back with 'arrow catching' where they took someone who had spent a great deal of time and practice learning how to catch arrows and put him in a more 'real world' situation and it did not go well for him.

I believe that the shooters weren't even using full draw on their bows but I could be mistaken on that, however I am sure that the safety equipment that they put on the arrows slowed them down even more than normal. Mini-missiles are also almost certainly smaller than arrows (since a rifle can hold 6 of them).

Of course the fact is that when you reduce things to that range you show that there is at least a sliver of possibility so I'm hesitant to say 'no, it can't be done'. It's just something that is extremely unlikely. Perhaps you could work with the player and allow them to 'stop' (not necessarily catch but at least block or deflect the mini-missile) by spending a point of Moxie. I'm not suggesting they automatically get to succeed in the action but to treat it like any other Moxie expenditure against an incoming attack where they flip the roll with the 'explanation' for what happened being that they were able to use their incredibly reflexes to pull off some superhuman feat.

My artificially intelligent spaceship is psychic. Your argument it invalid.

CoalPoweredPuppet CoalPoweredPuppet's picture
Stop using Logic!

Okay, you have sold me. My bad guy won't catch the good guy missiles. Thank you for your input.

Benny89 Benny89's picture
Not to even mention RPG-7

Not to even mention RPG-7 standard misslies are not the fastest or cutting-endge misslies you can fire from personal launcher today. There are way faster missles than that.

So now imagine how fast can be missles in EP where technology is so advanced.

I treat EP Seekers as only below Railguns when it goes for velocities.

EP already lets you roll half of your Frey vs things like Railguns or Firearms and Seekers which already should show you how fast are even base transhumans compare to us.

BUT! to give you different way of being super fast combat monster:

If you have Synth morph, High Freerunning + Pneumatic Limbs (+20 to freerunning) and Nacroalgorythms going (so you have effective 40 SOM) you can have 120-130 effective Freerunning which if used in Full Defense (freerunning can be used instead of Frey as per corebook) is Freerunning/2 +30 (Full Defense bonus to roll) giving you 90-99 roll vs incoming range attacks. So here is your typical super fast cyborg/future soldier/genetic super human that can dodge dance bullets and seekers :). You can dodge wholes squad fire of railguns with that + Moxies as not many enemies have weapon skills above 60-70 and one overload grenade + neuropath can quickly debuff them for -60 to all actions or one overload grenade/seeker to -30. Or Zap round + Overload for -60 so with your 90-99 Full Defense you can pretty much dodge everything.

But catching is imo out of question :D. Not to mention seekers can be remotely detonated by simple mental command so even catched ones will go off and deal full damage (epicentre) vs Frey roll which can put you out of epicentre at least (well, you won't dodge 10-20m explosion radius totally :D)

I allow however to shot down thrown grenades if player character has at least Speed 2 or Mental Speed implant/software. By mechanic you can catch and throw back grenades (REF + 2x COO roll if I remember correctly) so it should also be possible to shot grenade mid-air considering EP smartlink system, augmented reflex, aim and railguns.

Hope that will give you some hope ;). Also synths > Furies. You can be super duper biomorph- zap rounds/shock will still put you down given enough rounds (every zap will still give you -30 to all actions so if you add to that other debuffs like overload nade or toxins you look at rolling vs shock -60 almost all the time and then you are out of fight as biomorph), not even mention how good Narcoalgorythms are on combat synth character vs sloppy and slow chemical drugs. And Robotic enchancements + software plugins can give you way more combat potential (Mental speed alone as software for perma +3 INIT is super good).

Xagroth Xagroth's picture
CoalPoweredPuppet wrote:Okay,

CoalPoweredPuppet wrote:
Okay, you have sold me. My bad guy won't catch the good guy missiles. Thank you for your input.

Give the situation a twist... See if you can make a logical "whops" about that ammo! Like it hits the guy but doesn't explode nor does much more damage than a normal bullet from a gun... IF you have some way for the weapon to be hacked, or the ammo to be sabotaged or...

Because a guy very fast and good in a fight is a roadbump in EP. But a guy who somehow has compromised either the player's tacnet, the armscomp of their minimissile launcher, or their frigging supply lines (be it a hack on the fabbing machines with a backdoor that disables all smart ammo fired at him, or whatever) can be truly terrifying.

Be sure, however, that you can justify the situation and that the players are not doomed to total failure with that sample of baddassitude. Specially if you need them to defeat the guy, since it's possible that they decide to bail against someone who seems to have compromised them so much.

Lazarus Lazarus's picture
Actually, I misunderstood

Actually, I misunderstood part of the premise and that's important. For some reason I thought that it was a player who wanted to catch the missile (a big issue with that being that if you don't institute some kind of 'limiter' such as the Moxie expenditure they will probably try and do that a lot making mini-missiles useless against them).

What is the end goal of the bad guy catching the missile? Is it just to show off how badass they are? I can possibly think of ways to do that as a one-off (if the bad guy could get access to the tacnet they might plant a virus that lets them take control of the missile so that it flies into their hand and doesn't explode. Characters will see the same thing but later on when things have cooled down you can do a 'reveal' where they realize the guy wasn't as unbelievable as they thought, as an example).

On the other hand if your goal is to get the one player to calm down on the mini-missiles because you think they are imbalanced there might be other ways to go about that.

My artificially intelligent spaceship is psychic. Your argument it invalid.

Lazarus Lazarus's picture
Benny89 wrote:. . .If you

Benny89 wrote:
. . .If you have Synth morph, High Freerunning + Pneumatic Limbs (+20 to freerunning) and Nacroalgorythms going (so you have effective 40 SOM) you can have 120-130 effective Freerunning which if used in Full Defense (freerunning can be used instead of Frey as per corebook) is Freerunning/2 +30 (Full Defense bonus to roll) giving you 90-99 roll vs incoming range attacks. So here is your typical super fast cyborg/future soldier/genetic super human that can dodge dance bullets and seekers :). You can dodge wholes squad fire of railguns with that + Moxies as not many enemies have weapon skills above 60-70 and one overload grenade + neuropath can quickly debuff them for -60 to all actions or one overload grenade/seeker to -30. Or Zap round + Overload for -60 so with your 90-99 Full Defense you can pretty much dodge everything. . . .

Except that the way Eclipse Phase works is that the lower roll wins in the contested action. Not the one with the greater MoS. So if you have a 90-99 dodge roll and someone rolls a 12 they have about an 81% chance to hit you even with your massive dodge (assuming you haven't impaired their odds so badly that a 12 is a miss and excluding Moxie since that is in very limited supply). Yes, you can burn Moxie to help out but you won't be using it on odd freak occurrences where they beat your roll. You're going to be burning through it really, really quickly.

Either way, the thing that is really causing them to miss isn't your massive dodge roll. It's the extreme -60 penalty they take, because if they beat that penalty your odds of dodging don't change if you have a massive dodge or just a moderate one.

(edit: Whoops. I just realized I'm wrong about the system. The person who succeeds is the person with the higher successful roll, not lower, so if they succeed with a 12 you have a huge chance to beat them. Never mind.)

My artificially intelligent spaceship is psychic. Your argument it invalid.

ThatWhichNeverWas ThatWhichNeverWas's picture
Minicomment away!

I always think of Seekers as being more akin to 40mm grenades than full blown RPGs. I don't know enough about RL weapons to know how much of a difference that is, but I think the idea of running around with a guided grenade launcher is easier to parse, and probably is more sensible from a tactical point of view.

Another note for the original topic: even if you could get your hand around an incoming seeker without it going off, that doesn't mean it stops. More likely it keeps going along with the flesh from what used to be your arm.

For a BBEG? Laser point defence. Rules wise, you can express this as shots from too far away automatically failing, Rolling Beam instead of Fray, or having a minimum roll requirement for the shot (The target always rolls a miumum of X to fray), or any mixture of these.

In the past we've had to compensate for weaknesses, finding quick solutions that only benefit a few.
But what if we never need to feel weak or morally conflicted again?

Lazarus Lazarus's picture
The round is probably around

The round is probably around the size of the 40mm grenade (probably a little smaller, in fact) but performance-wise (velocity of the round) the RPG-7 is probably a good real life baseline. 40mm rounds have a totally different performance profile and could never hit a target 3000m away (extreme range for a mini-missile). It isn't that they lack the accuracy. The velocity of the round is simply insufficient to carry it that far (back of the envelope calculations are that the absolute maximum range of a 40mm round is around 590m given their muzzle velocity of about 75 m/s)

My artificially intelligent spaceship is psychic. Your argument it invalid.

Benny89 Benny89's picture
Um, what? Higher MOS wins.

Um, what? Higher MOS wins. Considering first thing you should do as combat character in the beginning of every fight is debuff enemies (zap rounds, neuratech, overload) to give them -60 to their rolls it's usually around 30-40 rolls vs 90-99. So you have much higher chance of dodging then they have of hitting you. You have higher chance of rolling any number above 30-40 while they can only roll below that. So usually I roll in 80% if cases higher than them. And even if you roll lower lets say against heavy hitter (you should not worry about small things like burst fire or sniper rifles if you build combat moster and stack armor) you can always use Moxie to upgrade success to critical success and dodge it anyway. Not to even mention EP mechanic where you can reroll roll with -10 penalty (cumulative). You have a lot of room for -10 rolls with 99 base roll.

Since I play combat monster myself that makes me usually dodge 80% of incoming shots after enemies debuff. I just have much higher odds of success and tools for it.

EDIT: NVM I have seen your edit :P. Please ignore abvove.

Lazarus Lazarus's picture
While my posting was

While my posting was incorrect, higher MoS is not correct either. Most of the time with Opposed Rolls it is the higher die roll that wins (assuming that both rolls succeed). Higher skill does still give you the edge since, as in your example, the defender's roll of 50 will beat an attacker's roll of 52 since a 52 is a failure for the attacker while a 50 is a success for the defender. It is complicated a little further because a critical success will always beat a standard success (meaning an attacker who rolled an 11 would succeed even against the defender who rolled a 50 unless the defender spent a Moxie to turn their standard success into a critical success).

MoS has absolutely nothing to do with who wins. The mechanism causes an interesting phenomenon because a lower roll gives you a larger MoS but also makes it more likely that your roll can be beaten. It's an interesting unique aspect to EP's challenge resolution system and it is that sort of odd, non-intuitive aspect that caused me to think earlier this morning that your high dodge roll wouldn't help you. As I said (and you noted) I was mistaken, however, because it is higher roll, not lower roll that wins.

My artificially intelligent spaceship is psychic. Your argument it invalid.

Lazarus Lazarus's picture
I think catching is out

I would like to reverse an earlier statement. Even as a sort of 'special effect' for spending Moxie or something I think catching a mini-missile is out. I was just looking up Seekers because I wanted to be sure I wasn't missing something (I think the way the rules handle seekers is a bit clumsy since you would probably not fire unless you have a lock and while getting a lock is probably skill based and a seeker can still miss even if you have a lock that probably has nothing to do with the skill of the firer) and I came across this:

EP. pg 339 wrote:
Seekers are a combination of automatic grenade launcher, micromissile, coilgun, and smart munitions technology. Unlike traditional launchers of the past, miniaturization allows the manufacture of seeker micromissile launchers in personal weapon sizes. Seeker rounds are fired at high-velocity via rings of magnetic coils, after which the micromissile or mini-missile uses scramjet technology to propel itself and maintain high velocities over great distances.

Taking that as written mini-missiles are far faster than bullets (and probably faster than rail guns at reasonable ranges). Scramjets need crazy high velocities before they can even begin to function (quick Google seems to indicate the lower range of a scramjet is about mach 6). It is possible you might want to reconsider aspects of that to be inaccurately written fluff and instead say that seekers use ramjets since the recoil of magnetically accelerating a mini-missile to mach 6 is probably pretty severe but that is probably a discussion for another thread.

It should probably also be noted that as written seekers cannot be used in a vacuum.

Of course you as a GM could decide to handwave nearly all of the fluff and say that they are far slower and carry their own oxidizers making them suitable for use in space, but I'm simply referring to fluff as written.

My artificially intelligent spaceship is psychic. Your argument it invalid.

Benny89 Benny89's picture
Lazarus wrote:.

Lazarus wrote:
.

It should probably also be noted that as written seekers cannot be used in a vacuum.

You mean like they SHOULD not be able to function in vacuum (due to real life sience) or that corebook says that? Because I don't remember from corebook anything about seekers not functioning in vacuum.

Also it's worth to remember that there is "real life" aspect in EP but also a mechanical ones that just need to be there for game to be playable and enjoyable. For example game says you can't put Body Armor over synethic with combat armor which in "real life" makes no sense. Same with Liquid Thermite eating through armor while (quoting) "nova-hot plasma stream" of Plasma Rifle does not. Or EMP not working on anything in EP. And lot of other stuff- for example discussed here "dodging" lasers and Mach 6 railgun shells....

EP already heavy "punish" GMs that have no science backgroud or knowledge about physics, astronomy, math or computer science/engineering. My GM was struggling for months (came from fantasy RPGs and is Art Master) to be able to run system and he didn't catch most of science things in EP (and players can exploit that easly as there is a LOT of things EP does not explain due to them being obvious for people with science background).

Also seekers are described as able to turn and manouver with homing system to hit targets behind covers or from indirect fire etc. I am not weaponary expert but how scramjet missle with at least Mach 6-7 velocity is able to turn that fast? This is just game mechanic :).

Lazarus Lazarus's picture
Benny89 wrote:. . .You mean

Benny89 wrote:
. . .You mean like they SHOULD not be able to function in vacuum (due to real life sience) or that corebook says that? Because I don't remember from corebook anything about seekers not functioning in vacuum. . .

Sorry. I could have been clearer on that. What I mean is that if you take the fluff to be 'real' then it would mean that Seekers can't be used in a wide variety of situations*. Not that the rules actually state that.

As for turning and hitting targets behind cover, that's one of the things that's extremely vague. It certainly would be possible for a high speed missile if fired out doors. You would probably have to be firing it nearly straight up so it can turn and come down on someone a reasonable distance away. Slower missiles would obviously have a much tighter turning radius but no where are we ever given much information as too how tight the turning radius is. I've always assumed that, even at the far lower speeds that I originally believed them to have, they never had a tight enough turning radius to make a turn down a hallway, but I realize now that is just my 'head cannon' and there's nothing in the books to support that.

Steering at high speed to a target in a more or less straight line is much less of an issue. We have real world missiles today with speeds at least in the same general neighborhood that do this just fine (lots of air-to-air and surface-to-air missiles are in the Mach 4 range). There's little in physics that would say a mini-missile can't do that.

*'Can't be used' is sort of a loaded term. Since the mini-missile is magnetically accelerated to a pretty healthy velocity (for various reasons I retract my initial assessment that it has to be accelerated to at least Mach 6 before the engine can engage but the round is still magnetically accelerated to speeds well in the range of bullets) it could be used in a vacuum, just not as a guided weapon and with far shorter ranges than those listed.

My artificially intelligent spaceship is psychic. Your argument it invalid.

CordialUltimate2 CordialUltimate2's picture
Our GM allowed our Gunbunny

Our GM allowed our Gunbunny to shutdown incoming missiles but on Speed 4 with Mental Speed and 4 full-auto railguns.

Maybe that's the countermeasure OP is looking for

Also 1 baddie doesn't stand a chance against 4 PCs. Some are bound to win initiative and start piling on wound penalties.

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Xagroth Xagroth's picture
CordialUltimate2 wrote:Our GM

CordialUltimate2 wrote:
Our GM allowed our Gunbunny to shutdown incoming missiles but on Speed 4 with Mental Speed and 4 full-auto railguns.

I think you can't stack mental speed augments with physical speed augments... so Speed 4 is the limit, and only really hard to get for physical actions. Then again, firing a bunch of micromissiles and getting a player to waste all of his actions into "AA duty" is a win, since that tied-up can be done with an autonomous drone :p

Anyway. Please consider how the "first edition" (the one not currently in Beta) had 2 versions of how rolls worked. One was Blackjack-like (the one who rolls highest without surpassing the target value wins) and the other tried to be more simpler (the one closest to 01 wins), with both counting doubles as criticals (failure if over the target value, success if under), and moxie to invert dice.

Finally, if the objective was to show an overentusiastic player that one weapon is not, in fact, a solution to all firefights, I would simply go to the root of the problem: namely, terrain. Explosives are not the best tools for a job done close to the central reactor/main storage tanks for volatiles/station's hull... Not to mention that the weapons can have automatic safeties that the players have to override (I would ask for a weapon roll to let the player decide if he wants or not to have that disabled, and let him switch to another weapon if he succeeds and decides that using a less indiscriminate weapon would be best. If he fails... wasted action, the weapon did not fire because of the safeties!).

CordialUltimate2 CordialUltimate2's picture
Mechanicaly you could reach

Mechanicaly you could reach 12 actions 4 physical (1 per action phase) and 8 mental (2 per action phase). It doesn't really make sense that MRDR increases your mental processing capabilities but it is RAW.

I second the terrain suggestion.
There are 3 main ingredients to a good encounter:
- the space
- the actors
- other ;-)

Exurgents wanna eat your ass and you are low on ammo? Register to mobile gear catalogue at eldrich.host.mesh! ORDER NOW! FOR FREE PLASMA MINIMISSILE PACK! *explosive delivery options included

Benny89 Benny89's picture
CordialUltimate2 wrote:Our GM

CordialUltimate2 wrote:
Our GM allowed our Gunbunny to shutdown incoming missiles but on Speed 4 with Mental Speed and 4 full-auto railguns.

Maybe that's the countermeasure OP is looking for

Also 1 baddie doesn't stand a chance against 4 PCs. Some are bound to win initiative and start piling on wound penalties.

Hm, my combat monster has 40 REF and 40 INT when he is on narcoalgorythms plus +3 Initiative from Mental speed gives him total of 19 Initiative before rolling k10 which I think is max init you can have. Never lost in initiative roll yet. Of course GM may just copy your build or simply place enemy with 30 base Init because "GM" but our GM thinks its lazy to copy builds of players.

I don't think you can go higher than 19

ThatWhichNeverWas ThatWhichNeverWas's picture
Scramjets are cool but make no sense in context.

Lazarus wrote:
The round is probably around the size of the 40mm grenade (probably a little smaller, in fact) but performance-wise (velocity of the round) the RPG-7 is probably a good real life baseline. 40mm rounds have a totally different performance profile and could never hit a target 3000m away (extreme range for a mini-missile).

I misunderstood - I thought you were using the RPG-7 as a general baseline, not just for velocity.
My response was more more general - intended use, explosive yield, projectile size ect.
As for flight speed...

Lazarus wrote:
Taking that as written mini-missiles are far faster than bullets (and probably faster than rail guns at reasonable ranges). Scramjets need crazy high velocities before they can even begin to function (quick Google seems to indicate the lower range of a scramjet is about mach 6).

As per the RAW, a single round of 4 turns is 3 seconds. The projectile must therefore travel 3km in 0.75s, or 3 seconds if we say it takes a whole round to travel.
As V=(2S/T) we have end speeds from from (2*3000m/3s) = 2km/s to (2*3000m/0.75s) = 8km/s or in other words Mach 5.8 to Mach 23 aka bonkers fast.
I tend to say they have MH engines, because why not.

In the past we've had to compensate for weaknesses, finding quick solutions that only benefit a few.
But what if we never need to feel weak or morally conflicted again?

Lazarus Lazarus's picture
ThatWhichNeverWas wrote:. .

ThatWhichNeverWas wrote:
. . .As per the RAW, a single round of 4 turns is 3 seconds. The projectile must therefore travel 3km in 0.75s, or 3 seconds if we say it takes a whole round to travel.
As V=(2S/T) we have end speeds from from (2*3000m/3s) = 2km/s to (2*3000m/0.75s) = 8km/s or in other words Mach 5.8 to Mach 23 aka bonkers fast.
I tend to say they have MH engines, because why not.

Actually assuming a round travels its entire maximum distance in a 'round' for any game (for the purposes of figuring out how fast something moves) is not a good choice, especially when you are dealing with rounds that are less than about 5 seconds. There are lots of things such as mortars or air-to-air missiles that could exceed the time. We still tend to resolve them in the same round because it is an enormous pain tracking such rounds over multiple turns and so use a convenience to simplify. It doesn't mean the rounds travel faster, just that we are admitting that what we are doing is a game and not a simulation (even though there may be some elements of simulation that are considered such as 'how much room does a seeker round need to make a turn?').

As written seekers apparently use chemical (scramjet) motors. There would never be such a thing as a metallic hydrogen scramjet because it doesn't make any sense. The two are very different mechanism. That isn't to say you couldn't, as a Ref, handwave and say in your campaign that they use motors that aren't scramjets, but I probably still wouldn't use MH. MH needs either massive pressures to store or else (in EP lore) a magnetic field to hold them metastable. The first case would simply add a prohibitive amount of weight to the round and the second case would mean you have a real risk of rounds exploding because their battery dies or an electrical fault (how much redundancy can you put in the EM field generator of something that small?). It would probably be much more practical to simply be a solid rocket motor with its own oxidizer (perhaps an electric solid propellant for better stability and in flight control given EP's advanced technology). Nice and simple and reliable.

My artificially intelligent spaceship is psychic. Your argument it invalid.

ubik2 ubik2's picture
Lazarus wrote:...it could be

Lazarus wrote:
...it could be used in a vacuum, just not as a guided weapon and with far shorter ranges than those listed.

You could use something like a reaction control system for guidance. Obviously, you wouldn't get the turn radius available in atmosphere. Also, you didn't bring this up, but a scramjet typically gets oxygen from the atmosphere, but it would be easy to modify it to have an oxygen source.

Assuming these projectiles are about the same mass as those fired by a 40mm grenade launcher (230g), you'd want the muzzle velocity to be around 75 m/s for reasonable recoil (Mach 6 is right out). You might be able to fire the rocket some while in the barrel, like the Javelin for a minor boost. I'd assume that the "scramjet" is some adaptive design that's just a normal rocket until it gets to scramjet speeds, and then switches mode.

Lazarus Lazarus's picture
ubik2 wrote:Lazarus wrote:..

ubik2 wrote:
Lazarus wrote:
...it could be used in a vacuum, just not as a guided weapon and with far shorter ranges than those listed.

You could use something like a reaction control system for guidance. Obviously, you wouldn't get the turn radius available in atmosphere. Also, you didn't bring this up, but a scramjet typically gets oxygen from the atmosphere, but it would be easy to modify it to have an oxygen source.

Assuming these projectiles are about the same mass as those fired by a 40mm grenade launcher (230g), you'd want the muzzle velocity to be around 75 m/s for reasonable recoil (Mach 6 is right out). You might be able to fire the rocket some while in the barrel, like the Javelin for a minor boost. I'd assume that the "scramjet" is some adaptive design that's just a normal rocket until it gets to scramjet speeds, and then switches mode.


Adding a reaction control system on top of the scramjet system when some of these rounds are so small they are being fired from a pistol seems a bit excessive. Even then I think we can safely assume that a missile using only the RCS will be far less effective at tracking (meaning reduced ranges) over a missile using the scramjet and thrust vectoring (along with using its RCS because what would be the point in not using it?).

As for an oxygen source, yes, the rocket could carry it which would allow it to function in situations such as being used on Titan or Mars (where there is an atmosphere but it is oxygen poor). However, this doesn't fix the situation of using them in vacuum because you need to compress the incoming atmosphere to generate heat in order to ignite the fuel. If you have some design that does not require the compression of atmosphere it is no longer a ramjet/scramjet. It is simply a hypergolic rocket or some other design.

My artificially intelligent spaceship is psychic. Your argument it invalid.

ubik2 ubik2's picture
You're absolutely right that

You're absolutely right that scramjets in vacuum don't make sense. I'd go with a more liberal reading, and view it as something like the SABRE concept, where it can operate like a scramjet when there's atmosphere, and as a rocket when there's not (or you're not moving Mach 6).

In the EP world, doing things the cool high tech way generally wins out over what we really do. Obviously, anyone building rocket munitions is going to use a solid-fuel or hypergolics today, since you can leave the rocket in storage, don't have to deal with leaking/boiloff/embrittlement, or all the other problems the neat fuels have. In EP, I like to imagine they've solved those issues, and have clean hydrogen engines.

Of course, the toxicity of hypergolics (or the lead in solid-fuel munitions) isn't really a problem in EP with medicine as advanced as it is. I figure people in those habitats are just getting blasted with radiation all the time too, but they go in for a weekly checkup, and all the cancerous cells are just removed from their system. So long as it doesn't reach the level where you die in the next day, you don't have to worry.

Edit: thinking more about this, you could just gimbal the engine instead of RCS.

Lazarus Lazarus's picture
ubik2 wrote:You're absolutely

ubik2 wrote:
You're absolutely right that scramjets in vacuum don't make sense. I'd go with a more liberal reading, and view it as something like the SABRE concept, where it can operate like a scramjet when there's atmosphere, and as a rocket when there's not (or you're not moving Mach 6).

But at that point they should probably just say that it uses a SABRE rocket and not a scramjet (honestly, I'm fine with them being able to work in vacuum. Just don't say they're scramjets. It's like saying something is made out of iron and then when people want to stick magnets to it saying you didn't really mean iron).

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In the EP world, doing things the cool high tech way generally wins out over what we really do.

Yes and no. There's typically some pretty solid science behind how they do things. Yeah, the nanofabrication and digitization of personalities requires some handwaving but for the most part things behave in ways we can pretty well understand (even if we can't duplicate). The exceptions to this tend to be things like Pandora gates and Basilisk hacks but those are the product of alien technologies so they are a bit freer to fall into the area of 'we can't really explain it'.

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Edit: thinking more about this, you could just gimbal the engine instead of RCS.

I assumed that was how the rounds did the majority of their steering and the proposed RCS was added to deal with vacuum operations. The problem with this idea is that the round should be more maneuverable (i.e. have better range) in an atmosphere because it would use both the RCS and the gimbal (after all, there's no point in saving the RCS fuel).

My artificially intelligent spaceship is psychic. Your argument it invalid.

o11o1 o11o1's picture
Lazarus wrote:

Lazarus wrote:

But at that point they should probably just say that it uses a SABRE rocket and not a scramjet (honestly, I'm fine with them being able to work in vacuum. Just don't say they're scramjets. It's like saying something is made out of iron and then when people want to stick magnets to it saying you didn't really mean iron).

Agreed.I Actually didn't even see the scramjet stuff when I first read Seekers and was mentally assuming it was some sort of clever rocket-missile with optional aerofoils. A reliable hypergolic rocket with a gimbal on it seems like a nice "all Purpose" solution.

A slight smell of ions....

ubik2 ubik2's picture
To clarify the gimbal portion

To clarify the gimbal portion, that's just changing the angle of the rear thrust. It lets you turn in vacuum or atmosphere. In atmosphere, you could use fins, but those are useless in vacuum. In practice, we mainly use RCS for turning rockets because it's hard to gimbal an engine, engines have limited restarts, and engines can't generally run at low thrust. All of those are technical challenges that can be overcome without superscience, though.

I agree that turning characteristics should be better in a relatively dense atmosphere.

Not important for missiles, but RCS is also way easier for docking maneuvers than a gimbaled engine. To back up, you don't have to spin around, cancel your spin, and cancel your velocity.