A garden tractor battery would be fine !
2 9V batteries would not...they do NOT have the amperage (current) needed to reliably fire Copperheads.
Do not try the cigarette lighter trick in the car....this car circuit does not have enough amperage either (you will probably blow a fuse in the car)....how do I know this one ?
I'm an Electrical engineer for one of the big auto companies up in Michigan.

I personally use a 12V motorcycle battery to launch my Aerotech engines with Copperheads and for up to 4 engine Estes clusters. Works great, has plenty of current and capacity, and does not break your back carrying it to the launch site.

One word of advice....save the "J (blackjack) propellant type" Aerotech loads for lighter rockets....that is the lowest average thrust propellant Aerotech offers.

In general, for order of average thrust/burn rate from high to low this is the Aerotech propellant chart:

1) Warp9 "N propellant" fastest burning/highest avg. thrust
2) Blue Thunder "T propellant"
3) Red Line "R propellant"
4) "fast" White Lightning "W propellant"
5) Black Max (Fast Jack) "FJ propellant"
6) "standard" White Lighting "W propellant"
7) Black Jack "J propellant" slowest burning/lowest avg. thrust.

Note 1: Aerotech does not officialy denote between "Fast" and "standard" White Lightning.

Note 2: Not all of the above propellants are offered in the "Hobby line"/ non high-power RMS cases. Only Blue Thunder, "standard" White Lightning, and Black Jack are offered in the hobby line cases.

Note 3: one does not have to be HPR certified to use the following HPR cases: 29/60, 29/100, 29/120. Redline propellant is offered in a load for the 29-100 case in the form of the G77-R.

Note 4: The hobby-line RMS 29/40-120 load of G33J technically requires HPR certification to fly it due to total propellant mass being over 62.5 grams. This is due to our "friends" at the Gestapo...oops I mean BATFE.



The E18W should be fine in your SLS Laser X, but for a first flight I think I'd use the RMS 24 D15-4T instead....It will only get to 300' or so but it would give you an idea of the flight profile of the Laser. 1000' is kind of high for a first flight even in a rocket this large. I personally used the RMS24 D15-4T for the first flight of my Semroc SLS Hustler, which is bigger and draggier than the SLS Laser. It flew to about 300' and recovered fine. Also used that engine for my Enerjet Athena and '72 Enerjet Aero Dart clones for the maiden flight. It was a good choice.

__________________
When in doubt, WHACK the GAS and DITCH the brake !!!

Yes, there is such a thing as NORMAL, if you have to ask what is "NORMAL" , you probably aren't !
Failure may not be an OPTION, but it is ALWAYS a POSSIBILITY.
ALL systems are GO for MAYHEM, CHAOS, TURMOIL, FIASCOS, and HAVOC !