Learn Hardcore Spanish (Latin America): El científico lanzará un cohete pequeño desde el desierto. - The scientist will launch a small rocket from the desert.

Lanzará is the simple future tense (futuro simple) of the verb lanzar. It expresses an action that will happen. You form it by taking the infinitive (lanzar) and adding the future endings:
-é, ‑ás, ‑á, ‑emos, ‑éis, ‑án.
So lanzar + -á = lanzará (“he/she/it will launch”).

Could we use va a lanzar instead of lanzará, and what’s the difference?

Yes. Va a lanzar is the periphrastic future (ir + a + infinitive). Both express future actions, but:

Va a lanzar is more colloquial and common in spoken Spanish.
Lanzará sounds more formal or written.
Meaning is almost the same, though lanzará can feel slightly more distant or “official.”

Why is the adjective pequeño placed after cohete instead of before?

In Spanish the default position for descriptive adjectives is after the noun: cohete pequeño = “small rocket.” Adjectives before the noun (e.g. pequeño cohete) are possible but often add emphasis, stylistic nuance, or poetic tone.

What gender is cohete, and why does pequeño agree with it?

Cohete is masculine (even though it ends in ‑e). Therefore the article is un, and the adjective takes the masculine form pequeño. If the noun were feminine, both article and adjective would also be feminine.

What does desde mean here, and why not use de?

Desde means “from” in the sense of origin or starting point (both in space and time). Desde el desierto = “from the desert.”
While de can sometimes translate as “from,” desde is more precise when you want to emphasize the exact source or starting location.

Why is there a definite article before desierto? Could you omit it?

Spanish normally uses the definite article before generic places: el desierto = “the desert” (in general). Omitting it (desde desierto) sounds ungrammatical. You need desde el desierto to say “from the desert.”

How do you pronounce científico, and where is the stress?

Científico is pronounced [sjenˈtifiko]. The written accent on the í signals that the stress falls on the antepenultimate syllable: ci-en-TÍ-fi-co.

Why do we say el científico (with el), even though we’re introducing a scientist for the first time?

In Spanish you often use the definite article with professions when you speak about a specific person in context: El científico lanzará… implies a particular scientist you and the listener already know about or assume exists. If you said Un científico lanzará…, it would sound like “A scientist (anyone) will launch…” more generic or hypothetical.