Can I connect grenades with a detonator and use it as a ranged weapon in combat?

Question

We've been dipping into Starfinder and I find myself playing a mechanic. I love the idea of using grenades to their fullest advantage, it's a fun, volatile weapon that turns up as loot too often not to make use of. However, as we level up the average grenade is not as useful as one-by-one weapons and so I thought about connecting them with a detonator and using that as a ranged weapon, or as a dropped weapon that I set off when at a safe distance. A sort of "grenade bomb".

But first, the facts:

Detonators: This conical device primes and detonates explosives (including grenades) with a push of a button. Programming a detonator to a specific package of explosives takes 1 minute, after which the detonator can be triggered in one of several ways. The detonator can be set to ignite its payload with the simple press of a button (no action), a four-digit command code (a move action), or a complex input method, such as scanning your retina or thumbprint (a full action). You choose the triggering method when setting the detonator. A detonator detonates its payload only if it is within 500 feet, but some detonators can make use of signal-boosting technologies at the risk of becoming vulnerable to countermeasures like signal jammers and other effects. Explosives have the same price, effect, and weight as grenades (see page 183). If you successfully set an explosive on a stationary object with a detonator using the Engineering skill, the explosive’s damage ignores half of the object’s hardness. (SCRB, 219)

And:

Grenades: Grenades are thrown weapons that detonate in an explosive radius when they reach the target...The DC of the save is equal to 10 + half the grenade’s item level + your Dexterity modifier. Any penalty you take to your attack roll also applies to this save DC. (SCRB, 183)

Ok, now, from these descriptions, I think it's possible. The detonator is a little bit confusing because it talks about grenades and explosives as separate where explosives can damage a stationary object. So I wouldn't be using this grenade bomb to damage an object specifically. It would be against creatures.

Questions, and I'm wondering if this might just be GM discretion:

• Would this grenade bomb be a ranged weapon or something that I have to plan and place? I.E. Could it be prepared in advance (takes one minutes, but doesn't specify if that's in battle or beforehand) and used when needed?
• How many grenades can be connected to a detonator? Would there be penalties to my attack roll? How would one calculate the save against the grenade bomb?

Thank you all so much!

Answer 1

Unfortunately, this does not work entirely as you'd like

While the detonator doesn't give details about how you can attack with it, you can probably use the detonator as a 'failsafe' for missing with a thrown grenade. Because one of the options is a Free Action, you can use your action to throw the grenade to a location then detonate it as a Free action if it lands where you intended. You could also lay out one or more grenades to be detonated at you choice if you wished, instead of needing to pull the pin and attack with them.

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However, you can only explode one grenade per detonator. From the Detonator item, we can note that Usage is "1/use". Usage definition is found on the Weapons page, Ammunition subheader and I've bolded it here:

Weapons often employ electrical charges (typically stored in batteries), cartridges of ammunition, or individual missiles. A weapon’s capacity measures what size battery it uses or the number of cartridges it can hold, and its usage is how much ammunition it uses with each attack. You can use launchers to fire their corresponding missiles, which must be loaded individually. Reloading a weapon or inserting a new battery (including ejecting a spent cartridge or battery if necessary) takes a move action.

Detonators can only activate one piece of explosives (or grenade) per use. The use of plural in its description is likely to represent that they are re-usable if programmed to other explosives after using it, and because "explosives" naturally appears plural.

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What you can do

One option that is close to your intent is possible; you can set a trap with up to 4 grenades. By attaching 4 detonators to 4 grenades, you can lay out the payload somewhere and detonate it when enemies are within range. You would free activate two detonators, drop them, draw two more (move and standard-move) and activate them as well.

Answer 2

This is GM discretion territory.

What you are basically asking is if you can throw multiple grenades at once to deal increased damage. I'm not actually seeing how the detonator would even help in this situation, as the grenades detonate on impact, making the detonator pointless. As for throwing multiple grenades at once by tying them together, whether it's with a detonator or just some string, is purely a GM decision, since normally, you can only throw one at a time.

Wiring up grenades to detonators and leaving it around as a trap is certainly within the realm of doable, and is clearly intended, since grenades are even specifically called out as being able to be wired up to a detonator. Though, for stringing multiple grenades together, you'll want to check with your GM on what to expect for damage or if that's specifically doable, as stringing up multiple explosives together on a single detonator isn't necessarily covered.