这些天看到火箭降落以进行软着陆是一种常见的现象，并且是太空探索的未来。当然，许多科幻小说读者都熟悉在所谓的“单级到轨道”（SSTO）中起飞和着陆的火箭飞船，这在科幻小说中比较容易，但在现实生活中并不那么简单。目前，使用多级火箭进行太空发射，这是世界各地空间机构所接受的技术。到目前为止，还没有SSTO运载火箭，但我们确实有可重复使用的火箭级。大多数人已经看到SpaceX第一阶段安置在驳船或着陆垫上，或者Blue Origins火箭安全返回其“巢穴”。这些是回到栖息地的第一阶段。这些可重复使用的发射系统（通常称为RLS）并不是一个新概念;航天飞机有可重复使用的助推器，可以将轨道飞行器送到太空。然而，猎鹰9（SpaceX）和新格伦（蓝色起源）的时代是一个相对较新的时代。其他公司，如RocketLab，正在寻求提供可重复使用的第一阶段，以便更经济地进入太空。目前还没有完全可重复使用的发射系统，尽管这种车辆的开发时机已到。在不久的将来，这些相同的发射系统将把人员带到太空舱上，然后返回发射台进行翻新以备将来的飞行。为什么我们之前没有单级到轨道和可重复使用的车辆呢？事实证明，离开地球引力所需的力量需要分阶段的导弹;每个阶段执行不同的功能。此外，火箭和发动机材料为整个项目增添了重量，航空航天工程不断寻找火箭部件的轻质材料。 SpaceX和Blue Origin等公司的出现改变了人们对发布的看法，他们使用重量较轻的火箭部件并开发了可回收的第一阶段。这项工作将获得更轻的火箭和有效载荷（包括人类将进入轨道及以外的胶囊）。但是，SSTO很难实现，不太可能很快发生。另一方面，可重复使用的火箭正在向前发展。要了解SpaceX和其他人正在做什么，了解火箭本身的工作方式非常重要（有些设计非常简单，以至于孩子们将它们作为科学项目建造）。火箭只是一个长的金属管，建在“阶段”，包含燃料，电动机和引导系统。火箭的历史可以追溯到中国人，他们被认为是在12世纪发明军事用途的。美国宇航局和其他航天机构使用的火箭基于德国V-2的设计。例如，使用Werner von Braun和其他德国工程师在第二次世界大战中创建德国军火库的原则设计了向太空发射许多早期任务的红石。他们的工作受到了美国火箭先驱罗伯特·H·戈达德的启发。向太空提供有效载荷的典型火箭分为两个或三个阶段。第一阶段是将整个火箭及其有效载荷发射到地球之外。一旦达到某个高度，那么第一阶段就会消失，第二阶段就会完成将有效载荷送到太空的剩余部分。这是一个相当简单的描述，一些火箭可能有第三级或更小的喷气机和引擎，以帮助引导它们进入轨道或进入其他地方，如月球或其中一个行星。航天飞机使用固体火箭助推器（SRB）帮助他们离开这个星球。一旦它们不再需要，助推器就会掉落并最终进入海洋。一些SRB被重新收集并重新装配以备将来使用，这使它们成为第一个可重复使用的助推器。
新加坡科技设计大学Assignment代写:可重复使用的火箭与太空飞行的未来
The sight of a rocket coming down to make a soft landing is a common one these days, and is very much the future of space exploration. Of course, many science fiction readers are familiar with rocket ships taking off and landing in what is known as “single stage to orbit” (SSTO), which is relatively easy to do in science fiction, but not so simple in real life. Right now, launches to space are done using multiple-stage rockets, a technology embraced by space agencies around the world. To date, there are no SSTO launch vehicles, but we do have reusable rocket stages. Most people have seen the SpaceX first stage settling down on a barge or a landing pad, or the Blue Origins rocket safely returning to its “nest”. Those are first stages returning to the roost. These reusable launch systems (commonly referred to as RLS), are not a new idea; the space shuttles had reusable boosters to take the orbiters to space. However, the era of the Falcon 9 (SpaceX) and New Glenn (Blue Origins), is a relatively new one. Other companies, such as RocketLab, are looking at supplying reusable first-stages for more economical access to space. There is not yet a completely reusable launch system, although the time is coming when such vehicles will be developed. In the not-too-distant future, these same launch systems will take human crews to space aboard capsules and then return to the launch pad to be refurbished for future flights. Why haven’t we had single-stage-to-orbit and reusable vehicles before now? It turns out that the power needed to leave Earth’s gravity requires staged missiles; each stage performs a different function. In addition, rocket and engine materials lend weight to the whole project, and aerospace engineering constantly looks for lightweight materials for the rocket parts. The advent of companies such as SpaceX and Blue Origin, who use lighter-weight rocket parts and have developed returnable first stages, is changing the way people think about launches. That work will pay off in lighter rockets and payloads (including the capsules humans will take to orbit and beyond). But, SSTO is very difficult to achieve and not likely to happen soon. On the other hand, reusable rockets are forging ahead. To understand what SpaceX and others are doing, it’s important to know how rockets themselves work (some designs are so simple that kids build them as science projects). A rocket is simply a long metal tube built in “stages” that contain fuel, motors, and guidance systems. The history of rockets goes back to the Chinese, who are thought to have invented them for military use in the 1200s. The rockets used by NASA and other space agencies are based on the design of the German V-2s. For example, the Redstones that launched many early missions to space were designed using the principles that Werner von Braun and other German engineers followed to create the German arsenal in World War II. Their work was inspired by American rocket pioneer Robert H. Goddard. A typical rocket that delivers payloads to space is in two or three stages. The first stage is what launches the entire rocket and its payload off Earth. Once it gets to a certain altitude, then the first stage drops away and the second stage takes on the job of getting the payload the rest of the way to space. This is a fairly simplistic description, and some rockets may have third stages or smaller jets and engines to help guide them to orbit or into trajectories to other places such as the Moon or one of the planets. The space shuttles used solid rocket boosters (SRBs) to help get them off the planet. Once they were no longer needed, the boosters dropped away and ended up in the ocean. Some of the SRBs were recollected and refitted for future use, making them the first reusable boosters.