7 Future Punishments

1-Spacing

Spacing is used for when a serious crime is committed in a spaceship, such as murder, rape, attempted mutiny, or something that endangers everyone aboard, and it is when the miscreant is placed in an airlock, either with or without a spacesuit, and either vented into outer space, or marooned on a planet where humans cannot breath the atmosphere. If put outside without a spacesuit it will lead to a quick and painful death but if the crime is thought to be truely dreadful, the criminal may be put outside in a  spacesuit with full oxygen tanks so that death takes a lot longer to come and he or she has time to think about what he or she did to earn the punishment.

2-Debanking

Normally used to punish political offenders, strikers, and those who go on the run rather then face trial for other offences, the criminal's bank accounts are either temporarily suspended or outright permanently closed. If the society is cashless, the person will have to at best depend on others and at worst either starve or steal from other people to survive. In serious cases, the punishment is extended to anyone who knowingly helps the offender and is made clear in the media so everyone knows  not to help that person.

3-Penal Transportation

The perpetrator is transported to a frontier world, either in cryosleep or in a very secure cell on board a prison starship or both. Violent criminals can use their violence against aggressive aliens, fraudsters can con aliens out of their land rights, and other things that are criminal on settled worlds can be a help on a poorly settled frontier world.

4-Cryosleep

Sometimes an offender is put in cryosleep. Someone in cryosleep cannot commit future offences,cannot escape from custody, does not cost much to hold,. and if new evidence comes out later and clears him or her of the offence, he or she can be woken, healed from any damage, compensated and set free with an apology.

5-Electro-gag

Normally used for cases of slander or verbally stirring up trouble, a securely attached taser is set around the criminal's throat that is set to go off if the person says more then a hundred words a day, or in some cases if the person speaks. One very patriarchal planet is known to make all women and girls wear one of these from the age of six for their whole lives. The more words the person says when the taser is activated, the worse the shocking gets.

6-Space Mining

Why not make use of the labour of the criminal? Such criminals are put on large asteroids or lifeless worlds in mines that have air pumped in, and are only fed if they mine a certain amount of ore per day. If they do escape, they will quickly die from a lack of air, and if they rebel en masse and try to take over the faculty, the air as a last resort can be vented into space killing all the criminals.

7-Replacement

This has only been legally done once, to a murderer, although there may have been one or two other cases where it was done illegally, but it is excessively rare and is only done for murder or perhaps manslaughter. The perp is surgically changed into a copy of the person they killed, including a gender change if that is needed, and then is mentally broken and then mentally rebuilt and trained so that they will act like the person they killed. They then are given to the family as a replacement son or daughter. It's extremely expensive, it's very experimental, and if the mental conditioning fails, at best the new faux son or daughter will run away, and at worst they might murder the entire  family that they have been assigned to.