Astra: A projectile missile invoked by reciting hymns,'Divyastras are not for every one only expert archers can have this Divyastras
Divyastras were astras used accompanied by chanting of the right sacred mantra. It is only when the correct mantra was chanted and used correctly...
No Divyastras could be used without an accompanying mantra that was essential to invoke the mighty power of the cosmic system.
when Divyastras were used in the earlier times... as was the mental capability of the user... so was the instrument available to him. Lord Vishnu alone was capable of handling the Sudarshan chakra and none else had the power in his times to use the Sudarshan chakra. Similar was the case with Brahmastra which was also limited to a very few individuals.
In Hindu mythology, an astra was a supernatural weapon, presided over by a specific deity. To summon or use an astra required knowledge of a specific incantation/invocation, when armed. The deity invoked would then endow the weapon, making it impossible to counter through regular means. Specific conditions existed involving the usage of astras, the violation of which could be fatal. Because of the power involved, the knowledge involving an astra was passed from a teacher to a pupil by word of mouth alone, and only following the establishment of the student's character. Certain astras had to be handed down from the deity involved directly, knowledge of the incantation being insufficient.
Astras come into importance mainly in the Ramayana and Mahabharata, where they are used in the great battles described in each epic. They are depicted as used by archers such as Rama, Arjuna, Bheeshma etc. The astras were generally invoked into arrows, although they could potentially be used with anything—Ashwatthama invoked an astra using a blade of grass as his weapon
Basically there were two types of the weapons used those days. Astras and Shastras (sha as in shall not as in sharp)
Astras were offensive weapons – Brahmastra, Pasupatastra, Agneyastra, Indrastra all come under this category
Shastras were defensive weapons – Shields, brahmadanda etc come under this category
Probably Brahmastra was a nuclear weapon as the description of this weapon in Mahabharata matches exactly that of a nuclear strike.
Aindraastra (Deity, Indra, god of weather): This would bring about a 'shower' of arrows from the sky.
Agneyastra (Agni, god of fire): The weapon discharged would emit flames inextinguishable through normal means.
Varunaastra (Varuna, god of water): The weapon discharged would release torrential volumes of water. This weapon is commonly mentioned as used to counter the Agneyastra.
Nagaastra (The Nagas): The weapon would have an inerring aim and take on the form of a snake, proving deadly upon impact.
Nagapaasha (The Nagas): Upon impact, this weapon would bind the target in coils of living venomous snakes.(in the Ramayana, it was used against Lord Rama and Lakshmana by Indrajit)
Vayvayaastra (Vayu, god of wind): This will bring about a gale capable of lifting armies off the ground.
Suryastra (Surya, god of the sun): This will create a dazzling light that would dispel any darkness about.
Vajra (Indra, god of weather): Target would be struck with bolts of lightning (vajra referring to Indra's thunderbolt).
Mohini (Mohini, an avatar of Vishnu): This will dispel any form of maya or sorcery in the vicinity.
Twashtar (Twashtri, the heavenly builder): When used against a group of opponents (such as an army), would cause them to mistake each other for enemies and fight each other.
Sammohana/Pramohana: This would cause entire hosts/armies to collapse in a trance.
Parvataastra: This would cause a Parvata/mountain to fall on the target from the skies.
Brahmaastra (Brahma, the Creator) This would destroy entire hosts at once. Could also counter most other astras.
Brahmasirsha (Brahma, the Creator): This is capable of killing devas. Was used by Ashwatthama on Parikshit. It is thought that the Brahmasirsha is the evolution of the Brahmastra.
Narayanaastra (Vishnu, the Preserver) This would create showers of arrows and discs. The astra's power would increase with the resistance offered to it. This weapon had to be obtained from Vishnu directly, and could be used only once. If the user were to attempt invoking it a second time, it would rebound on him, and possibly, his troops.
Vaishnavaastra (Vishnu, the Preserver) This would destroy target completely, irrespective of target's nature. Infallible. This weapon had to be obtained from Vishnu directly.
Pashupatastra (Shiva, the Destroyer): This would destroy target completely, irrespective of target's nature. Infallible. This weapon had to be obtained from Shiva directly.
braham dandastra-Brahma Danda is not an astra at all. That is the difference. Brahma Danda is a Y shaped stick or piece of wood. Sages have this danda and Kamandala (water vessel) with them always.
Haya-shira [The Horse-head] and Krouncha [The Wrester,] and two Impellers, one presided over by the power of Vishnu, and the other by the power of Rudra
Danda disc [Punisher disc] Dharma disc [Virtue-disc,] and like that kaala disc [Time-disc]; then oh, brave one, Vishnu disc; Brahma-shira [Brahma-crest]; the missile called the Aishiika missile [Grass-Blade missile,]
Modaki, [the Beater,] and Shikhari, [the Tower of Protection.]
Dharma paasha and kaala-paasha and Varuna paasha
shushka, [The Drier] and the other aardra, [The Drencher,] and even the missiles of Pinaaka and that of Narayana, [the missiles of god Shiva and Narayana,]
missile shikhari [The Tower,] and another the fond of Fire-god known as prathama [The Blower,] and a missile of god of wind
Haya-shira [The Horse-head] and Krouncha [The Wrester,] and two Impellers, one presided over by the power of Vishnu, and the other by the power of Rudra.
Vaidyadhara by its name, and a gem of sword named Nandana
Mohana, [The Stupefier,] the missile called Prasvapana [The Inducer of Sleep,] and the gentle Prashamana, [The Pacifier of enemy's anger.]
varshaNa, [the Rainer,] shoshana [the Drainer,] santaapana [the Humidifier,] vilaapana [the Weep-inducer,] and oh, prince, an unassailable intoxicator and a dear missile of Manmatha, namely Mohana [The Intoxicator,] and another the fond missile of gandharva-s namely maanava by its name, [The Humane missile,]
paishaca [The Monster missile.] taamasa and saumana missiles, the indomitable missiles like samvarta, mausala, satya, and then the maaya-maya missile; a solar missile the sequestrator of others' brilliance namely teja-prabha; the missile of Moon-god named shishira [The Cooler]; and a very deadly missile of tvaSTa namely sudaamana; and even the dangerous missile of bhaga namely shita-iSu,
Satyavanta, Satyakeerti, Dhristha, Rabhasa, Pratihaaratara, Paraanmuka, Avaanmukha, Lakshya, Alakshya, Dhridhanaabha, Sunaabha, Dashaaksha, Shatavaktra, Dashasheersha, Shatodara, Padmanaabha, Mahaanaabha, Dundunaabha, Svanaabha, Jyotisha, Shakuna, Nairaashya, Vimala, Yungandhara, Vinidra, Daitya, Pramadhana, Suchibaahu, Mahaabaahu, Nishkali, Virucha, Saarchirmaali, Dhritimaali, Vrittiman, Ruchira, Pitrya, Ssaumansa, and also thus Vidhoota, Makara, are two of them...Karaveerakara, Dhana, Dhaanya, Kaamaroopa, Kaamaruchira, Moha, Aavarana, and thus Jrimbhaka, Sarvanaabha, Varana..