4 ms·

Stupid question probably: Why are they trying to land it on a tiny barge in the sea, instead of trying to land on land?

AdamTReineke 12y ago
I assume to get the accuracy down. Once they prove they can hit that target reliably, they'll be trusted to try over land (where missing can have much bigger consequences).
Tuna-Fish 12y ago
Because if they fail badly and the rocket slams down hard, the remaining fuel and oxidizer in the tank is going to blow up like a very respectably sized bomb. It won't quite demolish a city block, but you certainly don't want to be anywhere near it. Until they can be sure they can reliably control it during descent, they are choosing their landing sites so that even in the very worst case, it can't come down on top of someone. This pretty much means it has to come down in the Atlantic.
- FrojoS 12y ago
  In addition to this, it will be required for the middle booster of the Falcon Heavy, which has its first flight next year and which will be too far away from land at separation for a boost back.
softbuilder 12y ago
I can think of several reasons, but the most significant is that the launch takes place over the ocean.
colechristensen 12y ago
If they don't have the precision to land on a tiny barge at sea (in calm seas), they don't have the precision to safely land anywhere reasonable. The worst case with a botched ground landing is something like dropping a blockbuster on a random, possibly populated area. The FAA won't allow them to attempt a non-sea landing until they've demonstrated several sea landings (along with much technical documentation).
marze 12y ago
Much easier to get FAA approval, and less propellant is required compared to reversing course completely to land near the launch site on land. Launch trajectory is always over water for US launches, so if the rocket fails there are fewer people to hit below.
ngoldbaum 12y ago
It's a big win to buy, build, and outfit the barge instead of paying an insurance payment to do the landing on land.
maaku 12y ago
Because the trajectory of where this thing ends up is in the ocean (on purpose -- think about failure modes to see why).
deleted 12y ago
[deleted]
exDM69 12y ago
In addition to what everyone else said: location and range safety. The launch sites they use were built for non-recoverable launch vehicles which are dropped to the sea. The launch sites have a narrow range eastwards, and SpaceX needs to adhere to the restrictions despite being able to land the boosters safely. This means that their rockets will inevitably be going over the sea.
InclinedPlane 12y ago
Incremental testing. They don't even have a landing site built yet, nor FAA permits for that. But get a few landings on a barge down and they'll improve confidence in the process a great deal.
Gravityloss 12y ago
1. You launch eastwards so you get the bonus speed from earth's rotation. 2. You launch over the ocean (or other sparsely populated areas) for safety purposes. All rockets so far have dropped stages or engines on the way. 3. To get to orbit, you have to do mostly horizontal acceleration (8 km/s or so). That's why the rocket points eastwards soon after launching, and staging happens already far from the launch site and why the first stage has a lot of horizontal velocity towards east. You don't want to fly a dog-leg as that wastes energy.
- trose 12y ago
  You have some valid points but I think you may be incorrect on this one. > 1. You launch eastwards so you get the bonus speed from earth's rotation Once the ship leaves the ground the earth's rotation has little to do with the flight except for landing location. source: I play KSP
  - Gravityloss 12y ago
    In Florida (28 degrees north) the earth surface travels at 400 m/s eastwards. (earth circumference * cos(28) / day) A spacecraft that would launch from the ground and start westwards, would, after gaining the first 400 m/s relative to its starting point only be stationary relative to the earth's center. Then after 800 m/s, it would travel at 400 m/s westwards. Say if your orbital velocity is 8.0 km/s. Your total delta vee would be 8.4 km/s. In comparison, an eastward flying rocket would start from 0.4 km/s , and would need rocket propulsion only for the remaining 7.6 km/s. A 10% saving compared to the westward rocket! In reality it's a bit more complex as you don't launch straight east or west anyway, and ISS is at a 50 degree inclination etc...
    - peeters 12y ago
      Exactly, and this is maximized by putting launch sites close to the equator. This is one reason why the European Space Agency launches from South America, by the way: > Kourou lies at latitude 5°3', just over 500 km north of the equator. Its nearness to the equator makes it ideally placed for launches into geostationary transfer orbit as few changes have to be made to a satellite’s trajectory. > Launchers also profit from the ‘slingshot’ effect, that is the energy created by the speed of the Earth’s rotation around the axis of the Poles. This increases the speed of a launcher by 460 m per second. These important factors save fuel and money, and prolong the active life of satellites. http://www.esa.int/Our_Activities/Launchers/Europe_s_Spaceport/Europe_s_Spaceport2 http://www.esa.int/Our_Activities/Launchers/Europe_s_Spacepo...

I assume to get the accuracy down. Once they prove they can hit that target reliably, they'll be trusted to try over land (where missing can have much bigger consequences).

Tuna-Fish 12y ago

Because if they fail badly and the rocket slams down hard, the remaining fuel and oxidizer in the tank is going to blow up like a very respectably sized bomb. It won't quite demolish a city block, but you certainly don't want to be anywhere near it. Until they can be sure they can reliably control it during descent, they are choosing their landing sites so that even in the very worst case, it can't come down on top of someone. This pretty much means it has to come down in the Atlantic.

FrojoS 12y ago
In addition to this, it will be required for the middle booster of the Falcon Heavy, which has its first flight next year and which will be too far away from land at separation for a boost back.

softbuilder 12y ago

I can think of several reasons, but the most significant is that the launch takes place over the ocean.

colechristensen 12y ago

If they don't have the precision to land on a tiny barge at sea (in calm seas), they don't have the precision to safely land anywhere reasonable. The worst case with a botched ground landing is something like dropping a blockbuster on a random, possibly populated area. The FAA won't allow them to attempt a non-sea landing until they've demonstrated several sea landings (along with much technical documentation).

marze 12y ago

Much easier to get FAA approval, and less propellant is required compared to reversing course completely to land near the launch site on land. Launch trajectory is always over water for US launches, so if the rocket fails there are fewer people to hit below.

ngoldbaum 12y ago

It's a big win to buy, build, and outfit the barge instead of paying an insurance payment to do the landing on land.

maaku 12y ago

Because the trajectory of where this thing ends up is in the ocean (on purpose -- think about failure modes to see why).

deleted 12y ago

[deleted]

exDM69 12y ago

In addition to what everyone else said: location and range safety. The launch sites they use were built for non-recoverable launch vehicles which are dropped to the sea. The launch sites have a narrow range eastwards, and SpaceX needs to adhere to the restrictions despite being able to land the boosters safely. This means that their rockets will inevitably be going over the sea.

InclinedPlane 12y ago

Incremental testing. They don't even have a landing site built yet, nor FAA permits for that. But get a few landings on a barge down and they'll improve confidence in the process a great deal.

Gravityloss 12y ago

1. You launch eastwards so you get the bonus speed from earth's rotation. 2. You launch over the ocean (or other sparsely populated areas) for safety purposes. All rockets so far have dropped stages or engines on the way. 3. To get to orbit, you have to do mostly horizontal acceleration (8 km/s or so). That's why the rocket points eastwards soon after launching, and staging happens already far from the launch site and why the first stage has a lot of horizontal velocity towards east. You don't want to fly a dog-leg as that wastes energy.

trose 12y ago
You have some valid points but I think you may be incorrect on this one. > 1. You launch eastwards so you get the bonus speed from earth's rotation Once the ship leaves the ground the earth's rotation has little to do with the flight except for landing location. source: I play KSP
- Gravityloss 12y ago
  In Florida (28 degrees north) the earth surface travels at 400 m/s eastwards. (earth circumference * cos(28) / day) A spacecraft that would launch from the ground and start westwards, would, after gaining the first 400 m/s relative to its starting point only be stationary relative to the earth's center. Then after 800 m/s, it would travel at 400 m/s westwards. Say if your orbital velocity is 8.0 km/s. Your total delta vee would be 8.4 km/s. In comparison, an eastward flying rocket would start from 0.4 km/s , and would need rocket propulsion only for the remaining 7.6 km/s. A 10% saving compared to the westward rocket! In reality it's a bit more complex as you don't launch straight east or west anyway, and ISS is at a 50 degree inclination etc...
  - peeters 12y ago
    Exactly, and this is maximized by putting launch sites close to the equator. This is one reason why the European Space Agency launches from South America, by the way: > Kourou lies at latitude 5°3', just over 500 km north of the equator. Its nearness to the equator makes it ideally placed for launches into geostationary transfer orbit as few changes have to be made to a satellite’s trajectory. > Launchers also profit from the ‘slingshot’ effect, that is the energy created by the speed of the Earth’s rotation around the axis of the Poles. This increases the speed of a launcher by 460 m per second. These important factors save fuel and money, and prolong the active life of satellites. http://www.esa.int/Our_Activities/Launchers/Europe_s_Spaceport/Europe_s_Spaceport2 http://www.esa.int/Our_Activities/Launchers/Europe_s_Spacepo...